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The last frontiers of wilderness: Tracking loss of intact forest landscapes from 2000 to 2013

The last frontiers of wilderness: Tracking loss of intact forest landscapes from 2000 to 2013 SCIENCE ADVANCES RESEARCH ARTICLE CONSERVATION BIOLOGY 2017 © The Authors, some rights reserved; exclusive licensee The last frontiers of wilderness: Tracking loss of intact American Association for the Advancement forest landscapes from 2000 to 2013 of Science. Distributed under a Creative 1 1 2 1 Peter Potapov, * Matthew C. Hansen, Lars Laestadius, Svetlana Turubanova, Commons Attribution 3 4 5 3 3 Alexey Yaroshenko, Christoph Thies, Wynet Smith, Ilona Zhuravleva, Anna Komarova, License 4.0 (CC BY). 6 7 Susan Minnemeyer, Elena Esipova An intact forest landscape (IFL) is a seamless mosaic of forest and naturally treeless ecosystems with no remote- ly detected signs of human activity and a minimum area of 500 km . IFLs are critical for stabilizing terrestrial carbon storage, harboring biodiversity, regulating hydrological regimes, and providing other ecosystem functions. Although the remaining IFLs comprise only 20% of tropical forest area, they account for 40% of the total aboveground tropical forest carbon. We show that global IFL extent has been reduced by 7.2% since the year 2000. An increasing rate of global IFL area reduction was found, largely driven by the tripling of IFL tropical forest loss in 2011–2013 compared to that in 2001–2003. Industrial logging, agricultural expansion, fire, and mining/resource extraction were the primary causes of IFL area reduction. Protected areas (International Union for Conservation of Nature categories I to III) were found to have a positive effect in slowing the reduc- tion of IFL area from timber harvesting but were less effective in limiting agricultural expansion. The certifica- tion of logging concessions under responsible management had a negligible impact on slowing IFL fragmentation in the Congo Basin. Fragmentation of IFLs by logging and establishment of roads and other infrastructure initiates a cascade of changes that lead to landscape transformation and loss of conservation values. Given that only 12% of the global IFL area is protected, our results illustrate the need for planning and investment in carbon sequestration and biodiversity conservation efforts that target the most valuable remaining forests, as identified using the IFL approach. INTRODUCTION scales. A number of global ecosystem wilderness and intactness maps Human modification of terrestrial ecosystems has a range of impacts, have been created over the past 30 years (3, 13, 14). Most have relied from a complete transformation at a local scale to distant effects such on outdated, coarse spatial resolution and static input data, which may as the impact of global climate change on ecosystem functions and dy- impede the accurate delineation of wilderness loss over time (15). namics (1, 2). No ecosystems may be considered truly intact because some Delineating forest wildlands includes two components: assessing degree of human impact is present everywhere (3). Alteration and frag- direct forest structural alteration (including forest conversion, tim- mentation of forest landscapes compromise their ecosystem functions, in- ber extraction, and indirect effects, such as human-ignited fires) and cluding loss of biological diversity and reduction of carbon storage (4, 5). the resulting fragmentation of the remaining forest landscapes due Forest wildlands, those forests least affected by human activity, to such changes. Satellite data provide the most feasible solution for have the highest conservation value in terms of the range of ecosystem recurrent global mapping and monitoring of human-caused forest services they provide (6–10). These areas are often irreplaceable in alteration and fragmentation (16). harboring biological diversity, stabilizing terrestrial carbon storage, We define an intact forest landscape (IFL) as a seamless mosaic of regulating hydrological regimes, and providing other ecosystem forests and associated natural treeless ecosystems that exhibit no remote- functions (11). Their ability to perform ecosystem functions and their ly detected signs of human activity or habitat fragmentation and are resilience to natural disturbance and climate change are functions of large enough to maintain all native biological diversity, including viable their size. Many “umbrella” mammal and bird species, whose conser- populations of wide-ranging species (15). The global IFL mapping is vation also may enhance the protection of co-occurring species, re- based on a set of clear and straightforward criteria, designed to enable quire large natural habitats to survive (12). Large forest wildlands satellite-based mapping (see Materials and Methods). The term “intact are the greatest terrestrial carbon stores, a function at risk from forest forest landscape” is not congruent with the term “primary forest” as conversion (deforestation) and degradation (10). Small forest areas, defined by the Food and Agriculture Organization of the United even if pristine, have less potential for preserving wide-range species Nations (FAO) (17), and the two must not be confused. Primary forests populations and have lower resilience to natural disturbance and are part of IFLs, which also include nonforest intact ecosystems where effects of climate change (4). Hence, thesizeof the wildland matters: climatic, soil, or hydrological conditions prevent tree growth, tempo- the larger the size, the higher the conservation value of the territory. rally treeless areas after the natural disturbance (for example, wildfires), Preservation of forest wildlands requires a robust mapping and and water bodies. IFLs may also include areas affected by low-intensity monitoring system that can be implemented at national to global and historic human influence, such as hunting, scattered small-scale shifting cultivation, and preindustrial selective logging. IFLs include 1 2 large fragments of primary forests with a minimum extent of 500 km , University of Maryland, College Park, MD 20740, USA. Laestadius Consulting LLC, 3 4 Silver Spring, MD 20901, USA. Greenpeace Russia, Moscow, Russia. Greenpeace while smaller fragments of primary forests may be found outside IFLs. Germany, Hamburg, Germany. Global Forest Watch Canada, Ottawa, Ontario, Here, we use the archive of Landsat satellite imagery to map the global 6 7 Canada. World Resources Institute, Washington, DC 20002, USA. NGO Transpar- extent of IFLs in the years 2000 and 2013, to locate changes due to ent World, Moscow, Russia. *Corresponding author. Email: potapov@umd.edu alteration and fragmentation, and to identify causes of change. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 1of13 | SCIENCE ADVANCES RESEARCH ARTICLE RESULTS retaining more than 40% of their respective forest zone as IFLs in the We assessed the distribution and dynamics of IFLs within the ex- year 2000. tent of present-day forest ecosystems. We defined “forest” as lands Globally, 30% of the world forest area (land with tree canopy cover with a tree canopy cover greater than 20% in the year 2000, using a of 20% or greater) was within IFLs in the year 2000. Most of the IFL global tree canopy cover data set (18) as a reference. The present- area (82.3%) is covered with forest. The rest is covered with intact day extent of forest landscapes (mosaics of forests, naturally treeless treeless ecosystems (montane grasslands, treeless wetlands, and ecosystems, and deforested areas) is referred to as the “forest zone.” burned areas as a consequence of wildfires) and a small fraction of The forest zone extends over 58 million km , or 44% of Earth’s ice- nonvegetated areas (water, rocks, and ice). free land area. The extent of IFLs in the year 2000 totaled 12.8 mil- From 2000 to 2013, the global IFL area decreased by 7.2%, a reduc- 2 2 lion km , or 22% of the forest zone area. tion of 919,000 km (Table 1). Tropical regions are responsible for 60% The IFLs form distinctive regional groupings (Fig. 1 and Table 1), of the total reduction of IFL area. In particular, tropical South America 2 2 each with a unique history of alteration and fragmentation. In the hu- lost 322,000 km of IFL area, whereas Africa lost 101,000 km .Tempe- mid tropics, IFLs are found in the Amazon and Congo River basins, rate and southern boreal regions contributed 21% to the global IFL area the islands of Borneo and New Guinea, and the Southeast Asian high- loss. Northern Eurasia alone lost 112,000 km of its IFL area. The re- lands. Tropical regions comprise 48% of the total global IFL area. In maining 19% of IFL area reduction occurred within the northern boreal dry tropical and subtropical regions, IFLs are scarce or absent due to forests of Eurasia and North America. Compared to the year 2000 IFL extensive conversions to agriculture, some of which happened many extent, the proportion of the IFL area reduction was lowest in the north- centuries ago. Within the temperate and southern boreal forests of ern boreal regions and in the temperate forests of South America and North America and Eurasia, IFLs remain only in small areas spared highest in Australia, Southeast Asia, Africa, and the temperate regions from commercial logging and agriculture. IFLs are abundant in north- of North America and Eurasia (Fig. 2). ern boreal forests, interrupted mainly by mining, extraction of fossil Three countries comprise 52% of the total reduction of IFL area: 2 2 fuels, and human-ignited wildfires associated with roads. Northern Russia (179,000 km of IFL area lost), Brazil (157,000 km ), and Canada boreal IFLs comprise 36% of the total global IFL area. (142,000 km ). Proportional to the year 2000 IFL area, the highest per- IFLs were found within 65 countries in the year 2000 (Table 2). centages of IFL area reduction were found in Romania, which lost all Three countries (Russia, Brazil, and Canada) account for nearly IFLs,and Paraguay,where 79% of IFL area was lost; Laos, Equatorial two-thirds of the global IFL area. These countries are followed by Guinea, Cambodia, and Nicaragua each lost more than 35% of their IFL the Democratic Republic of the Congo, Peru, the United States (pri- area (Fig. 3 and Table 2). Assuming that the loss of IFLs continues at marily Alaska), Indonesia, Colombia, and Venezuela, each con- the average rate between 2000 and 2013, Paraguay, Laos, Cambodia, tributing more than 2% to the global IFL area. French Guiana has and Equatorial Guinea will lose their entire IFL area during the next the highest proportion of intactness of all countries, with IFLs making 20 years. Another 15 countries will lose all IFLs within a 60-year period, up 79% of the forest zone. This country is followed by Suriname, including such IFL-rich nations as the Republic of the Congo, Gabon, Guyana, Peru, Canada, Gabon, and the Republic of the Congo, each Cameroon, Bolivia, and Myanmar. Fig. 1. The world’s IFLs. IFL extent for the year 2013, IFL area reduction from 2000 to 2013, and boundaries of geographic regions used for the analysis. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 2of13 | SCIENCE ADVANCES RESEARCH ARTICLE Table 1. IFL extent and area reduction per geographic region. IFL area IFL proportion *Forest IFL proportion Forest IFL IFL area reduction Geographic IFL 2000 area of the forest proportion of global IFL zone area 2013 area reduction 2000–2013, 2 6 region (km ×10 ) zone in within IFL area in 2 6 2 6 (km ×10 ) (km ×10 ) 2000–2013 (%) not attributed 2000 (%) 2000 (%) 2000 (%) to fire (%) Africa 9.08 1.00 11.0 99.8 7.8 0.90 10.1 10.1 Australia 1.01 0.13 12.4 55.6 1.0 0.10 21.9 15.3 South America, temperate 0.41 0.16 38.2 43.4 1.2 0.15 1.3 0.9 South America, tropical 14.70 4.43 30.1 98.9 34.6 4.11 7.3 7.1 North America, temperate 5.85 0.54 9.2 66.5 4.2 0.46 15.5 11.2 and southern boreal North America, 3.89 3.04 78.2 63.8 23.7 2.94 3.3 0.3 northern boreal Northern Eurasia, temperate and 11.96 1.23 10.3 69.8 9.6 1.12 9.1 7.4 southern boreal Northern Eurasia, 3.33 1.57 47.0 75.7 12.2 1.50 4.4 1.8 northern boreal Southeast Asia 7.38 0.72 9.8 93.7 5.6 0.62 13.9 13.9 World total 57.60 12.81 22.2 82.3 100.0 11.89 7.2 5.7 *Forest is defined here as land with tree canopy cover above 25%, as depicted by the global tree cover product (18). from infrastructure and logging sites (21.2%). Other causes includ- ed fragmentation by roads for mining and oil/gas extraction, pipe- lines, and power lines (12.1%) and expansion of the transportation road network (2.0%). At the regional level, we observed a diversity of leading IFL area reduction causes (Fig. 4 and Table 3), whereas for each particular region, a single cause accounted for more than 50% of the regional IFL area reduction. Using sample-based analysis and the annual forest loss data set (18), we found that 14% of the total IFL area reduction was due to direct alteration caused by logging, clearing, and fires. The remaining 86% was due to fragmentation by such disturbances and construction of infrastructure. The annual forest loss within IFLs may be used as a proxy to understand the temporal dynamics of IFL area reduction. In tropical regions, the annual forest loss within IFLs increased during the past 13 years (Fig. 5). The average annual forest loss within IFL reduction area for the 2011–2013 period was triple the average for the 2001–2003 period for each of the three tropical regions, with the high- est increase observed in central Africa. Of the total IFL area in the year 2000, 12.4% fell within protected Fig. 2. Distribution of IFL area in the year 2000 and reduction of IFL area areas (PAs), with a management regime consistent with the Interna- 2000–2013 by geographic region. The y axis shows the initial IFL proportion tional Union for Conservation of Nature (IUCN) categories I to III of the forest zone in the year 2000. The x axis shows the reduction in IFL area (19). Australia and temperate South America have the largest propor- from 2000 to 2013 as the proportion of IFL 2000 area. The area of each bubble tion of IFLs under legal protection (47.4 and 43.7%, respectively), 2 6 indicates the IFL area in km ×10 . Values within each bubble represent the re- whereas temperate and southern boreal northern Eurasia (7.7%) gional IFL area in the year 2000 as a percent of the global total. and northern boreal regions (7.7% in North America and 5.2% in Eur- asia) have the lowest. Forty of the 65 countries, in which IFLs were We used stratified sampling to identify the primary causes of the present in the year 2000, had at least 10% of the IFL area under legal IFL area reduction. At the global level, the leading fragmentation protection. Uganda, the Dominican Republic, Thailand, and Cuba had and alteration agents were timber harvesting (37.0% of global IFL protected more than 90% of their IFL area. Some countries do not in- area reduction), agricultural expansion (27.7%), and wildfire spread clude any IFLs within category I to III PAs, including many Southeast Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 3of13 | SCIENCE ADVANCES RESEARCH ARTICLE Table 2. IFL extent and area reduction per country. IFL area IFL proportion IFL proportion IFL area reduction Country code IFL 2000 of the forest of global IFL Country name reduction 2000–2013, 2 3 (for Fig. 3) area (km ×10 ) zone in area in 2000–2013 (%) not attributed 2000 (%) 2000 (%) to fire (%) Angola AGO 2.9 0.3 0.02 13.7 13.7 Argentina ARG 39.9 6.5 0.3 2.0 1.8 Australia AUS 82.2 9.8 0.6 32.7 22.8 Belize BLZ 4.3 19.7 0.03 4.8 4.8 Bhutan BTN 6.4 19.3 0.05 15.5 15.5 Bolivia BOL 233.3 28.9 1.8 19.6 18.3 Brazil BRA 2476.1 31.7 19.3 6.3 6.2 Brunei BRN 2.0 35.1 0.02 17.0 17.0 Cambodia KHM 1.1 0.9 0.01 38.2 38.2 Cameroon CMR 52.8 13.4 0.4 25.2 25.2 Canada CAN 3040.3 51.0 23.7 4.7 2.3 Central African Republic CAF 8.7 1.5 0.1 34.4 34.4 Chile CHL 131.4 36.9 1.0 1.3 0.9 China CHN 45.0 1.6 0.4 11.5 11.2 Colombia COL 349.2 31.0 2.7 1.3 1.3 Costa Rica CRI 3.2 6.2 0.02 3.0 3.0 Côte d’Ivoire CIV 4.6 1.7 0.04 17.5 17.5 Cuba CUB 0.5 0.5 0.004 0 0 Democratic Republic COD 643.9 27.7 5.0 4.2 4.2 of the Congo Dominican Republic DOM 0.8 1.7 0.01 29.0 1.6 Ecuador ECU 53.3 22.3 0.4 5.3 5.3 Equatorial Guinea GNQ 4.2 15.8 0.03 45.2 45.2 Ethiopia ETH 3.7 1.4 0.03 9.6 9.6 Finland FIN 9.7 3.1 0.1 0.2 0.2 French Guiana GUF 65.4 79.1 0.5 5.7 5.7 Gabon GAB 108.8 41.2 0.8 22.9 22.9 Georgia GEO 9.0 18.3 0.1 0.7 0.7 Guatemala GTM 5.7 5.2 0.04 13.3 13.3 Guyana GUY 144.1 69.6 1.1 11.3 11.3 Honduras HND 6.7 6.0 0.1 28.6 28.6 India IND 33.7 5.6 0.3 1.6 1.6 Indonesia IDN 359.2 20.1 2.8 10.8 10.8 Japan JPN 1.2 0.4 0.01 0.01 0.01 continued on next page Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 4of13 | SCIENCE ADVANCES RESEARCH ARTICLE IFL area IFL proportion IFL proportion IFL area reduction Country code IFL 2000 of the forest of global IFL Country name reduction 2000–2013, 2 3 (for Fig. 3) area (km ×10 ) zone in area in 2000–2013 (%) not attributed 2000 (%) 2000 (%) to fire (%) Kazakhstan KAZ 4.4 16.6 0.03 2.3 2.3 Laos LAO 8.5 3.8 0.1 47.9 47.9 Liberia LBR 4.7 5.0 0.04 32.2 32.2 Madagascar MDG 17.2 7.2 0.1 19.0 18.5 Malaysia MYS 21.1 6.5 0.2 25.1 25.1 Mexico MEX 15.0 1.8 0.1 2.8 2.6 Mongolia MNG 11.7 12.6 0.1 12.5 0.4 Myanmar MMR 52.9 10.1 0.4 30.9 30.9 Nepal NPL 0.6 0.6 0.004 0 0 New Zealand NZL 43.1 25.4 0.3 1.3 1.2 Nicaragua NIC 10.3 8.0 0.1 38.1 38.1 Nigeria NGA 3.0 1.3 0.02 5.3 5.3 Norway NOR 1.8 1.4 0.01 1.0 1.0 Panama PAN 14.5 19.6 0.1 19.8 19.8 Papua New Guinea PNG 159.8 35.1 1.2 13.3 13.3 Paraguay PRY 44.5 11.1 0.3 79.3 79.3 Peru PER 567.2 68.5 4.4 6.1 6.1 Philippines PHL 4.0 1.6 0.03 9.5 9.5 Republic of the Congo COG 138.7 40.7 1.1 17.7 17.7 Romania ROU 1.0 0.6 0.01 100.0 100.0 Russia RUS 2744.3 28.3 21.4 6.5 4.3 Samoa WSM 0.7 23.8 0.01 0.6 0.6 Solomon Islands SLB 7.8 32.3 0.1 52.9 52.9 Suriname SUR 107.4 73.8 0.8 5.7 5.7 Sweden SWE 11.6 3.0 0.1 0.8 0.8 Tanzania TZA 4.1 0.8 0.03 2.3 2.3 Thailand THA 19.4 7.0 0.2 7.8 7.8 Uganda UGA 1.0 0.7 0.01 0.9 0.9 United States USA 539.3 14.2 4.2 7.9 0.2 Vanuatu VUT 0.7 7.5 0.01 1.1 1.1 Venezuela VEN 312.8 35.7 2.4 1.5 1.5 Vietnam VNM 4.1 1.7 0.03 25.5 25.5 Asian countries (Lao People’s Democratic Republic, Vietnam, Cambodia, IFL area reduction (Table 4). In Africa, North America, and Eurasia, and Philippines), Papua New Guinea, Ethiopia, Angola, and Nicaragua. the reduction of IFL area was more than 4 times higher outside PAs Using matching sampling analysis, we found that the reduction than inside PAs, whereas it was 2.6 times higher in Southeast Asia and of IFL area for reasons other than fire was 3.4 times higher outside almost double in tropical South America. PAs (6.2%) than within PAs (1.8%). We found a large difference in To study the effect of legal protection and voluntary forest man- most regions between protected and unprotected areas in terms of agement certification on IFL area reduction by logging, we analyzed Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 5of13 | SCIENCE ADVANCES RESEARCH ARTICLE Fig. 3. Distribution of IFLs by country in the year 2000 and reduction of IFL area 2000–2013. The y axis shows the IFL area in the year 2000. The x axis shows the reduction in IFL area from 2000 to 2013 as the proportion of IFL 2000 area. Country codes are given in Table 2. PAs and timber concessions in the three central African countries, Expansion of logging into intact forest areas has many direct where up-to-date spatial information on forest management exists: effects on ecosystem functions, including reduction of carbon stor- Cameroon, Gabon, and the Republic of the Congo. Some of the con- age (20), decrease of habitat suitability (6, 21), and increase of vul- cessions were certified to the Forest Stewardship Council (FSC) stan- nerability to human-induced wildfires (22, 23). Fragmentation of dard. Certified concessions had thesameorhigherproportionofIFL forest landscapes by logging and logging roads causes direct habitat area reduction than noncertified concessions, whereas the IFL area loss (24) and increases the incidence of poaching (25), resulting in loss wasatleast four timeslower in PAsthanintimber concessions species loss. Even within areas designated for sustainable forest (Table 5). management, like some tropical timber concessions, the construc- tion of new logging roads initiates a cascade of land use changes and subsequent reduction in landscape conservation value. The ex- DISCUSSION ample from the Republic of the Congo (Fig. 6) shows how expan- Causes of IFL area reduction sion of logging infrastructure and a new hydropower project have Industrial timber extraction, resulting in forest landscape alteration and markedly reduced IFL area. Agricultural expansion, forest fires, and fragmentation, was the primary global cause of IFL area reduction. In the potential increase of unregulated hunting (26) are coincident Africa and Southeast Asia, selective logging was the dominant IFL loss with the expansion of the logging road network. cause (77 and 75% of the total loss of IFL area, respectively), whereas Agricultural expansion was the second most important cause of clear-cutting was the main IFL loss cause in the temperate and southern IFL area reduction. In tropical South America, expansion of agri- boreal regions of North America and Eurasia (68 and 54%, respective- culture overall and of pastures in particular contributed 65 and ly). Therelativeproportion of forest loss and fragmentation within IFL 53% of the overall IFL area loss, respectively. Expansion of indus- reduction area depends on the logging method and the intensity of tim- trial crops (for example, soybean) was not detected as a cause of ber extraction. Clear-cuts caused a higher proportion of forest alteration IFL area reduction using our sample-based analysis. IFLs were (15% of the total IFL area reduction) compared to selective logging not directly affected by industrial crop expansion in South America (1.2%), with the remaining IFL reduction attributed to fragmentation because it mainly occurred in areas previously converted to pas- by logging sites and roads. Southeast Asia had a higher proportion of tures (27). In tropical Africa and Southeast Asia, slash-and-burn clearing within selectively logged areas than tropical Africa and South smallholder agricultural expansion contributed 23 and 15%, respec- America (1.4 versus 0.3% for each of the latter). tively, to the total IFL area reduction. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 6of13 | SCIENCE ADVANCES RESEARCH ARTICLE Establishment of oil palm plantations contributed 0.2% of the Forest fires associated with infrastructure and therefore assumed to total IFL area reduction. We found new oil palm plantations be human-induced accounted for 21% of the total IFL area reduction. affecting IFLs in all tropical regions (Fig. 7). Plantations usually fol- Fire-related degradationwas foundwithinall regionsexceptSoutheast low selective logging expansion and represent an example of how Asia. The absence of fires as an IFL degradation cause in Indonesia is industrial logging operations can set off a cascade of interventions explained by the fact that the remaining IFLs are located within that eventually result in the final conversion of natural forests to remote mountain areas, whereas fires are much more prevalent in industrial monoculture plantations (28). fragmented and degraded lowland forests. Fire was the main cause 2 3 Fig. 4. Regional reduction of IFL area (km ×10 ) and causes of change. Table 3. Sample-based assessment of the causes of IFL area reduction. 2 3 2 3 The IFL area reduction by proximate cause, km ×10 (standard error, km ×10 ) Total IFL Number Mining, oil area reduction of samples Timber Agriculture and Other transportation, 2 3 2 Wildfire and gas, (km ×10 ) (1 km each) harvesting pasture expansion tourism hydropower Africa 101.3 100 0 77.5 (0.4) 22.8 (0.4) 0 1.0 (0.1) Australia 27.4 50 6.6 (0.2) 0 0.5 (0.1) 17.6 (0.2) 2.7 (0.1) South America, 2.1 50 0.5 (0.01) 0.9 (0.01) 0 0 0.7 (0.01) temperate South America, 321.5 300 7.5 (0.3) 68.1 (0.8) 209.0 (0.9) 28.4 (0.5) 8.6 (0.3) tropical North America, temperate and 83.3 84 24.8 (0.4) 56.6 (0.4) 0 1.0 (0.1) 1.0 (0.1) southern boreal North America, 101.2 116 92.5 (0.3) 0 0 8.7 (0.3) 0 northern boreal Northern Eurasia, temperate and 112.1 113 23.8 (0.4) 60.0 (0.5) 0 26.3 (0.4) 2.0 (0.1) southern boreal Northern Eurasia, 69.5 87 39.2 (0.4) 1.6 (0.1) 0 28.8 (0.4) 0 northern boreal Southeast Asia 100.2 100 0 75.6 (0.4) 22.6 (0.4) 0 2.0 (0.1) Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 7of13 | SCIENCE ADVANCES RESEARCH ARTICLE of IFL area reduction in northern boreal regions (91% in North of disturbance. The highest percent of forest clearing was observed for America and 56% in northern Eurasia) and accounted for more than oil palm plantation establishment (43% of the total IFL area reduction) 20% of IFL reduction in temperate North America, temperate Eurasia, and forest fires (41%), followed by clear-cut logging (15%), pasture and Australia. Excluding fires as a cause of IFL degradation would (15%), and other agricultural expansion (8%). However, the core areas change the global IFL area reduction from 7.2 to 5.7% (Table 1) but of IFL also experience natural forest loss events. Intact landscapes are would not lead to notable changes in the ranking of regions by the not static in terms of land cover change. Large-scale wildfires, pest proportion of IFL area lost. attacks, and wind damage occur naturally in many temperate and bo- Energy production (oil and gas extraction and hydropower) and real forests, where they are followed by natural regeneration. Accord- mining operations are globally important causes of IFL area reduction ing to the global forest cover loss product (18), the total area of forest due to the fragmenting effect of their transportation infrastructure. Oil loss within IFL from 2001 to 2013 was 314,000 km ,or2.5%ofthe and gas extraction was the leading fragmentation cause in northern IFL area. This includes both anthropogenic and natural disturbances. Eurasia (specifically in the Russian Federation), accounting for 41% The IFL 2000–2013 change data set shows that 55% of the total forest of IFL reduction in the northern boreal and 23% in the southern bo- loss area fell within stable IFL areas and was therefore assumed to repre- real and temperate forests. Russia is the largest producer of crude oil sent natural ecosystem dynamics. However, for the tropical regions, the and the second largest producer of natural gas in the world. Recent proportion of natural disturbance within IFLs was small (8.6% of the expansion of oil and gas exploration and extraction in East Siberia total forest loss area within year 2000 IFLs). caused fragmentation of the forest wildlands through establishment of new pipelines and extraction infrastructure, usually accompanied Legal protection of IFLs by logging and human-ignited fires. Mining and mineral exploration In all regions, the proportion of the reduction of IFL area was lower (mostly for gold) played a significant role in Australia (64% of the total inside of PAs than outside of PAs (Table 4), suggesting that legal IFL reduction) and tropical South America (9%). protection was effective in preventing IFL loss. However, this con- Fragmentation generally dominatesoverforestclearingasafactor clusion may be invalid due to the nonrandom distribution of PAs of IFL area reduction. Their relative contribution depends on the type within IFL areas (29). To control for the varying vulnerability of IFLs to human alteration and fragmentation, we implemented a sample matching method to account for the nonrandom distribution of PAs. The results confirmed that legal protection has been effective at lessening the reduction of IFL areainall regionsexceptAustralia (where roads have been constructed near PA boundaries) and tempe- rate South America (where new tourist infrastructure has been devel- oped in a national park). However,when analyzing thecausesofIFL area reduction, we noticed that legal protection was not always an ef- fective way to limit agricultural expansion. Of the 10 PAs in Africa, classified as IUCN categories I and II that experienced more than 1% IFL area loss, 7 were subjected to smallholder agricultural expan- sion. Two of these PAs are in Andasibe-Mantadia National Park (in which all IFLs disappeared) and Tsaratanana Strict Nature Reserve Fig. 5. Annual proportion of the total forest loss within tropical forests that (in which 28% of the IFL area was lost). In both cases, slash-and-burn lost IFL status between 2000 and 2013. agriculture expanded within park boundaries. The same process was Table 4. IFL area reduction inside and outside IUCN category I to III PAs. Area-based estimate represents area calculated from the map. Sample-based estimate is based on matching sampling analysis performed only within portions of IFLs vulnerable for degradation. This analysis only considers the reduction of IFL area 2000–2013 that was not attributed to fire. Area-based estimate Sample-based estimate and standard error (SE) IFL 2000 within Region IFL area reduction IFL area reduction IFL area reduction IFL area reduction IUCN category within PAs (%) outside PAs (%) within PAs, % (SE, %) outside PAs, % (SE, %) I–III PAs (%) Africa 10.8 1.6 11.2 5.5 (0.72) 25 (1.37) Australia and New Zealand 47.4 9.6 20.5 54.6 (1.57) 44.1 (1.57) Temperate South America 43.7 0.4 1.3 1.6 (0.40) 1.1 (0.33) Tropical South America 15.1 2.0 8.0 8.0 (0.86) 14.6 (1.12) Temperate North America 34.0 1.1 16.4 5.2 (0.70) 24.6 (1.36) Temperate Northern Eurasia 7.7 1.4 7.9 3.2 (0.56) 17.5 (1.20) Southeast Asia 12.7 4.6 15.2 6.8 (0.80) 17.9 (1.21) Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 8of13 | SCIENCE ADVANCES RESEARCH ARTICLE observed in Virunga National Park (Democratic Republic of the IFL area reduction worldwide. Standards for responsible forest Congo), which lost 3.3% of its IFL area due to agricultural expansion. management, including those of the FSC, seek to balance forest- Another cause of IFL area reduction within PAs is the development based economic development with conservation. FSC regards IFLs of new infrastructure. In some cases, new transportation infrastructure as a type of high conservation value forest, and the FSC standard causes fragmentation, as in Domogled-Valea Cernei National Park states that their degradation should be avoided. In 2014, the General (Romania). In other cases, the development of infrastructure for Assembly of FSC adopted a motion (Motion 65) that calls upon FSC tourism and recreation caused IFL area reduction, for example, the ex- to do the following: “within IFL cores ensure that Certificate Holders pansion of the road network in Puyehue National Park (Chile) and the implement protection measures (for example, set-asides, legal construction of a ski resort within Sochinsky National Park (Russia). protected areas, conservation reserves, deferrals, community reserves, Although some of these infrastructure projects were developed to in- indigenous protected areas etc.) ensuring management for intactness” crease PA income and stimulate public awareness of the importance of (30). If Motion 65 is implemented, we should, at least, in the future, nature conservation, they nevertheless had the effect of reducing the expect IFL fragmentation to proceed more slowly within FSC-certified extent of remaining forest wildlands through fragmentation. concessions than in noncertified concessions. Our results from the Many IFLs contain high-value timber resources, and logging period 2000–2013 suggest that the pace of IFL fragmentation due and associated fragmentation by roads are the leading causes of to selective logging in central Africa is faster within FSC-certified Table 5. IFL extent and area reduction within logging concessions in three central African countries. The spatial database of logging concessions in Cameroon (2013), Republic of the Congo (2013), and Gabon (2012) was obtained from the World Resources Institute (www.wri.org/our-work/project/congo- basin-forest-atlases). IFL area IFL area IFL area IFL area IFL proportion IFL proportion reduction reduction reduction reduction of FSC-certified Country of total concession 2000–2013 2000–2013 2000–2013 2000–2013 concession area area in 2000 (%) within the within all within FSC-certified within PAs in 2000 (%) country (%) concessions (%) concessions (%) (IUCN category I–III) (%) Cameroon 40.5 38.4 25.2 41.1 84.5 0.3 Republic of the Congo 42.4 61.6 17.7 37.1 41.9 4.8 Gabon 48.4 29.7 22.9 37.9 37.0 9.0 Fig. 6. Stages and causes of the IFL area reduction and landscape transformation in the Republic of the Congo (map center at 16°0′E1°12′N). The infrastructure and IFL extent within the area are shown as of September 2016. The map shows expansion of settlements and regional transportation and logging roads from the year 2000 until 2016. Logging road expansion caused the reduction of IFL area. IFL extent was mapped for the years 2000, 2013, and 2016. New settlements and agricultural areas appeared along existing and established roads. Logging expansion triggered forest fires that initiated from the roads and forest clearings. In September 2016, a water reservoir was constructed within the remaining IFL area, which caused continuous fragmentation and transformation of the surrounding landscape. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 9of13 | SCIENCE ADVANCES RESEARCH ARTICLE Fig. 7. Examples of the ongoing expansion of oil palm plantations within IFLs in tropical regions. Each example shows IFL degradation depicted in year 2015 or 2016 cloud-free Landsat-8 satellite images. All maps have the same scale. The IFL boundary in 2013 is marked by a yellow line, and the IFL boundary for the year 2000 is marked by a red line. Oil palm plantations established before the year 2013 are denoted as “A,” and plantations established after 2013 are denoted as “B”. (1) Gabon; image subset centered at 11°47′E 2°7′N; image date, 12 January 2015. (2) Indonesia; subset centered at 139°45′E 7°21′S; image date, 10 May 2016. (3) Peru; subset centered at 75°7′W 8°15′S; image date, 24 June 2016. concessions than outside them, due to selective logging and fragmen- portation infrastructure, agricultural areas, and logging sites were as- tation by logging road construction (Table 5). By definition, selective sumed to be caused by humans and thus were treated as an IFL logging and establishment of associated infrastructure in an IFL re- reduction factor. Although lightning strikes can ignite forest fires, sev- duce its area. Although we do not know the degree to which IFL frag- eral studies have found that most fires in the vicinity of infrastructure mentation is actively avoided by logging operations, it is evident that and logging sites are of human origin, in boreal (22, 34)aswell asin selective logging within FSC-certified concessions is a significant temperate (35, 36)and tropical forests(37). However, large fires may driver of IFL area reduction in central Africa. For other regions, suf- be of natural origin even if colocated with infrastructure (38, 39). Our ficiently detailed spatial information on logging concessions and cer- approach has been to construct a set of mapping rules that can be tification is largely unavailable, precluding similar analysis. applied consistently at the global scale. For burned areas, our rule as- sumes that fires in the vicinity of areas with human access are likely to Regional approaches to IFL monitoring have a human cause. Regional conservation specialists (40)havechal- National projects focused on characterizing “primary forests,”“high lenged the utility of applying globally consistent criteria at regional conservation value forests,” or “wilderness areas” are complementary scales, specifically in interpreting the causes of fires in boreal Canada. to the global IFL mapping initiative. Such maps often provide In response to these concerns, our global analysis differentiates IFL information on smaller fragments of high conservation value forests reduction due to fire from other causes. located outside of the largest wilderness areas. The work of Global The IFL concept is defined to map the large unfragmented tracts of Forest Watch Canada (GFWC) represents an example of regional primary forests. A different set of criteria, using a smaller threshold for IFL mapping that uses different criteria from our global method. minimum patch size, would be needed to map small fragments of GFWC criteria allow for inclusion of all burned areas within IFLs, re- primary forest. Our earlier work in central Africa and insular South- gardless of the cause of fire, and require a smaller minimum area for a east Asia showed that substantial areas of primary forests exist outside patch to qualify as an IFL (31, 32). The GFWC IFL map has been of IFLs. We found that 38.6% of the primary forest area in the Dem- updated for the year 2013 (33), allowing for a comparison of regional ocraticRepublicofthe Congo(41) is located outside of IFLs, whereas and global IFL maps. The GFWC map for 2013 showed that Canada on the island of Sumatra, Indonesia, the proportion is 73.2% (28). The has a total IFL area that is 1.4 times larger than the one shown in our method presented here can be used to identify conservation priority global map. However, 98.6% of the intact area from our global map is areas at the regional and national levels if the criteria for minimum included in the GFWC map, illustrating agreement on the location eligible patch size and alteration are adjusted for this purpose. and extent of core wilderness areas. The standard method presented in this paper is capable of Accuracy of the global IFL map providing a globally consistent characterization of the extent of IFLs To assess the accuracy of the IFL 2000–2013 change map, we used the and its change over time. However, for regional mapping initiatives, same 1000 random samples that were used to assess the causes of IFL regional relevance may be a higher priority than global consistency. area reduction. The samples were interpreted separately from the gen- Regional assessments may wish to deviate from the standard global eration of the map. The sampling design made it possible to estimate method by using criteria that are adapted to the regional context, as commission error (that is, change that had been falsely attributed to GFWC does. It is important to be clear on the differences in criteria as human causes) but not omission error (human-caused change that they may explain a major part of the seeming discrepancy between a had been overlooked, that is, that was not reflected in the change regional and a global map. map). Visual interpretation of Landsat imagery and of high-resolution An important difference between the global IFL assessment imagery available through Google Earth confirmed that 92% of the presented here and the regional IFL assessment produced by GFWC sampled area of IFL area reduction had been correctly classified. It is the treatment of fire-related disturbances. It is typically not possible was not possible to confirm whether the alterations for the remaining to determine whether a fire had a natural origin or was caused by sampled area (8%) were human-caused based on Landsat or high spa- people. In the global assessment, burned areas in the vicinity of trans- tial resolution satellite imagery. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 10 of 13 | SCIENCE ADVANCES RESEARCH ARTICLE A partial field validation of the IFL 2000 map by Greenpeace in Hawaii in 2016 adopted a motion (Motion 048) that “encourages Russia and GFWC (42, 43) confirmed that intact areas within the states, the private sector and international financial institutions to: a. boreal and temperate forests of European Russia and Canada had avoid loss and degradation of primary forests, including intact forest been correctly classified. An alternative approach to validation focused landscapes;b.promote conservation of primary forests, including in- on forest structure to differentiate intact forests from forests within tact forest landscapes” (51). National approaches to protecting IFLs degraded or altered landscapes. Studies by Margono et al. (28)and include expansion of the PA network and the establishment of a sys- Zhuravleva et al. (41) used data from the Geoscience Laser Altimeter tem for wilderness area management similar to that of the United System to examinethe tree canopy structureinsideand outsideofIFLs States (52). Large forested wildlands often straddle international in Sumatra (Indonesia) and the Democratic Republic of the Congo. Their boundaries, highlighting the need for effective international conserva- results revealed a statistically significant difference in average forest tion strategies (10). IFLs provide a framework for maintaining large, height between intact forests and other forests (fragmented and altered). contiguous, and often transnational blocks of forest wildlands. The high carbon stocks found within IFLs illustrate their potential benefit IFL role in climate change mitigation to climate change mitigation strategies. This study has demonstrated The primary forests that remain within IFLs represent the most signif- that legal protection is an effective policy for reducing the degradation icant carbon pool within the tropical biome (44). Using a benchmark of IFLs. We suggest that IFLs should be considered when existing PA tropical forest carbon map produced for the early 2000s (45), we networks are revised and expanded. We also suggest that monitoring estimate that the total biomass carbon pool in the tropical forest zone of forest intactness should be treated as an important aspect of nation- was 243 Gt C around year 2000, of which IFLs stored 97 Gt C (40%). al and global forest assessments. The average carbon density was greater in IFLs than in the rest of the tropical forest zone: 3.7 times higher in Africa, 3.4 times higher in South America, and 1.7 times higher in Southeast Asia. MATERIALS AND METHODS IFLs in the boreal and temperate regions differ from those in the The extent of the forest zone was mapped using the global year 2000 tropics by having lower biomass per unit area and lower produc- tree canopy cover data set (18) with a 20% tree canopy cover thresh- tivity than managed forests. In the year 2000, the average growing old. Inland water bodies and naturally treeless ecosystems were includ- stock in North America and Eurasia was 1.4 times higher in forests ed in the forest zone. Fragments of land in the forest zone with a 3 3 2 outside IFLs (145.5 m /ha) than within IFLs (103.1 m /ha) (46). This contiguous area smaller than 500 km were excluded from consider- has historical reasons. In the past, temperate and southern boreal ation. Geographic regions within the forest zone (Fig. 1) were delineated forests have been cleared, converted into managed forests, or fragmen- using natural boundaries between forested areas. The boundary be- ted by infrastructure, leaving mostly low productivity forests (specifi- tween northern boreal and southern boreal/temperate regions in cally, peatlands and mountains) as IFLs (42). Nevertheless, the vast North America and northern Eurasia was based on Landsat data areas of boreal IFLs represent a large and relatively stable above- analysis and represents the de facto dividing line between lands that and belowground carbon storage that plays an important role in the have, and have not, been subjected to industrial logging as of the global climate system. Although the recent increase in boreal wildfire year 2013. frequency and intensity (39) threatens long-term aboveground carbon An IFL is defined as a seamless mosaic of forests and asso- storage in northern forests, it has been shown that IFLs have a lower ciated natural treeless ecosystems that exhibit no remotely de- fire frequency compared to fragmented and developed areas (22). Per- tected signs of human activity or habitat fragmentation and is mafrost protection is another important IFL function. Road and large enough to maintain all native biodiversity, including viable pipeline constructions have multiple direct and indirect effects on populations of wide-ranging species (15). An IFL includes both permafrost, increasing its vulnerability to thawing (47). Almost 52% forest and naturally treeless ecosystems. Two main criteria were (2.6 million km ) of the total continuous and discontinuous perma- used to distinguish an IFL patch from the surrounding landscape: frost area within forest zone in North America and Eurasia is located (i) ecosystem alteration and (ii) landscape fragmentation by infra- within the remaining IFLs (48). structure and disturbance. Areas that have been altered or man- aged (through agriculture, logging, and mining) were excluded, along with a buffer zone of 1 km (53)oneithersideofinfra- CONCLUSIONS structure elements (roads, pipelines, power lines, and navigable Intactness is a good indicator of the comprehensive conservation value rivers). Past disturbances that occurred more than 30 to 70 years of a forest landscape (7, 8). It is related to specific ecosystem values, ago, scattered small-scale shifting cultivation, nonindustrial timber such as ecosystem integrity and resilience to natural disturbances and harvesting by indigenous forest dwellers, and low-intensity distur- to ongoing climate change. It is also related to other forest ecosystem bance not directly observable in remotely sensed data (hunting functions, such as biodiversity (49). It can be reduced very rapidly, in a and forest grazing) were not considered IFL alteration or frag- matter of months and years, by increased fragmentation and access, mentation factors. An IFL patch must have (i) a minimum size even without changes in tree canopy cover. On the other hand, intact- of 500 km , (ii) a minimum width of 10 km, and (iii) a minimum ness is hard to gain, at least within a short time span. That is why corridor/appendage width of 2 km. Any patch that falls below these intact landscapes should be treated as having high (or even the high- thresholds, for example, due to fragmentation, logging, or fire, was est) conservation value. The conservation value of an intact area is rejected in its entirety. dependent on its size because many umbrella mammal and bird spe- Source data for IFL mapping and monitoring were taken from cies require large natural habitats to survive (12, 50). That is why the the global archive of medium spatial resolution Landsat satellite size of the intact area should always be taken into consideration when imagery. We used a collection of single-date Landsat images (15)to assessing wildland conservation value. The Congress of the IUCN held map IFLs for the year 2000. Landsat images circa year 1990 were used Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 11 of 13 | SCIENCE ADVANCES RESEARCH ARTICLE 3. E. W. Sanderson, M. Jaiteh, M. A. Levy, K. H. Redford, A. V. Wannebo, G. 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Davidson, Positive feedbacks in the fire dynamic of closed canopy tropical forests. (GMTED2010) (U.S. Geological Survey, 2011). Science 284, 1832–1835 (1999). 38. M. P. Calef, A. D. McGuire, F. S. Chapin, Human influences on wildfire in Alaska from 1988 Acknowledgments: We would like to thank all organizations and their representatives who through 2005: An analysis of the spatial patterns of human impacts. Earth Interact. 12, participated in the global Intact Forest Landscapes mapping and monitoring initiative, 1–17 (2008). including Greenpeace, the World Resources Institute, Transparent World, WWF Russia, Luonto 39. E. S. Kasischke, D. L. Verbyla, T. S. Rupp, A. D. McGuire, K. A. Murphy, R. Jandt, J. L. Barnes, Liitto, and other regional nongovernmental organizations. We greatly appreciate help from E. E. Hoy, P. A. Duffy, M. Calef, M. R. Turetsky, Alaska’s changing fire regime—Implications remote sensing data interpretation specialists, Geographic Information Systems technicians, and for the vulnerability of its boreal forests. Can. J. For. Res. 40, 1313–1324 (2010). nature conservation experts who provided invaluable knowledge and assistance in the 40. P. Lee, Caution against using intact forest-landscapes data at regional scales. Ecol. Soc. 14, development and validation of the IFL data set. Funding: The IFL 2000–2013 global update was r1 (2009). funded by Greenpeace Russia and Global Forest Watch, an initiative of the World Resources 41. I. Zhuravleva, S. Turubanova, P. Potapov, M. Hansen, A. Tyukavina, S. Minnemeyer, Institute. Author contributions: A.Y., L.L., C.T., P.P., and S.T. designed the IFL concept. S.T., I.Z., N. Laporte, S. Goetz, F. Verbelen, C. Thies, Satellite-based primary forest degradation A.K., E.E., and P.P. performed global IFL change mapping. S.M. provided data and analysis of assessment in the Democratic Republic of the Congo, 2000–2010. Environ. Res. Lett. 8, FSC-certified concessions in central Africa. W.S. performed the national IFL mapping in Canada. 024034 (2013). P.P performed sample-based analysis of IFL change causes and effectiveness of legal protection. 42. A. Y. Yaroshenko, P. V. Potapov, S. A. Turubanova, The Last Intact Forest Landscapes of The manuscript was prepared by P.P., M.C.H., and L.L. with contributions from S.T., A.Y., C.T., S.M., Northern European Russia (Greenpeace Russia and Global Forest Watch, 2001). and W.S. Competing interests: The authors declare that they have no competing interests. 43. P. Lee, D. Aksenov, L. Laestadius, R. Nogueron, W. Smith, Canada’s Large Intact Forest Data and materials availability: The IFL extent and change maps in GIS format are available on Landscapes (Global Forest Watch Canada, 2003). the project website (www.intactforests.org/) and through the Global Forest Watch data portal 44. A. Tyukavina, A. Baccini, M. C. Hansen, P. V. Potapov, S. V. Stehman, R. A. Houghton, (www.globalforestwatch.org/). All tabular data needed to evaluate our conclusions are present in A. M. Krylov, S. Turubanova, S. J. Goetz, Aboveground carbon loss in natural the paper. Additional data related to this paper may be requested from the authors. and managed tropical forests from 2000 to 2012. Environ. Res. Lett. 10, 074002 (2015). Submitted 18 April 2016 45. S. S. Saatchi, N. L. Harris, S. Brown, M. Lefsky, E. T. A. Mitchard, W. Salas, B. R. Zutta, Accepted 29 November 2016 W. Buermann,S.L.Lewis,S.Hagen, S.Petrova, L. White, M. Silman,A.Morel, Benchmark Published 13 January 2017 map of forest carbon stocks in tropical regions across three continents. Proc. Natl. Acad. 10.1126/sciadv.1600821 Sci. U.S.A. 108, 9899–9904 (2011). 46. M. Santoro, C. Beer, O. Cartus, C. Schmullius, A. Shvidenko, I. McCallum, U. Wegmüller, Citation: P. Potapov, M. C. Hansen, L. Laestadius, S. Turubanova, A. Yaroshenko, C. Thies, A. Wiesmann, Retrieval of growing stock volume in boreal forest using hyper-temporal W. Smith, I. Zhuravleva, A. Komarova, S. Minnemeyer, E. Esipova, The last frontiers of series of Envisat ASAR ScanSAR backscatter measurements. Remote Sens. Environ. 115, wilderness: Tracking loss of intact forest landscapes from 2000 to 2013. Sci. Adv. 3, 490–507 (2011). e1600821 (2017). Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 13 of 13 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Science Advances Pubmed Central

The last frontiers of wilderness: Tracking loss of intact forest landscapes from 2000 to 2013

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SCIENCE ADVANCES RESEARCH ARTICLE CONSERVATION BIOLOGY 2017 © The Authors, some rights reserved; exclusive licensee The last frontiers of wilderness: Tracking loss of intact American Association for the Advancement forest landscapes from 2000 to 2013 of Science. Distributed under a Creative 1 1 2 1 Peter Potapov, * Matthew C. Hansen, Lars Laestadius, Svetlana Turubanova, Commons Attribution 3 4 5 3 3 Alexey Yaroshenko, Christoph Thies, Wynet Smith, Ilona Zhuravleva, Anna Komarova, License 4.0 (CC BY). 6 7 Susan Minnemeyer, Elena Esipova An intact forest landscape (IFL) is a seamless mosaic of forest and naturally treeless ecosystems with no remote- ly detected signs of human activity and a minimum area of 500 km . IFLs are critical for stabilizing terrestrial carbon storage, harboring biodiversity, regulating hydrological regimes, and providing other ecosystem functions. Although the remaining IFLs comprise only 20% of tropical forest area, they account for 40% of the total aboveground tropical forest carbon. We show that global IFL extent has been reduced by 7.2% since the year 2000. An increasing rate of global IFL area reduction was found, largely driven by the tripling of IFL tropical forest loss in 2011–2013 compared to that in 2001–2003. Industrial logging, agricultural expansion, fire, and mining/resource extraction were the primary causes of IFL area reduction. Protected areas (International Union for Conservation of Nature categories I to III) were found to have a positive effect in slowing the reduc- tion of IFL area from timber harvesting but were less effective in limiting agricultural expansion. The certifica- tion of logging concessions under responsible management had a negligible impact on slowing IFL fragmentation in the Congo Basin. Fragmentation of IFLs by logging and establishment of roads and other infrastructure initiates a cascade of changes that lead to landscape transformation and loss of conservation values. Given that only 12% of the global IFL area is protected, our results illustrate the need for planning and investment in carbon sequestration and biodiversity conservation efforts that target the most valuable remaining forests, as identified using the IFL approach. INTRODUCTION scales. A number of global ecosystem wilderness and intactness maps Human modification of terrestrial ecosystems has a range of impacts, have been created over the past 30 years (3, 13, 14). Most have relied from a complete transformation at a local scale to distant effects such on outdated, coarse spatial resolution and static input data, which may as the impact of global climate change on ecosystem functions and dy- impede the accurate delineation of wilderness loss over time (15). namics (1, 2). No ecosystems may be considered truly intact because some Delineating forest wildlands includes two components: assessing degree of human impact is present everywhere (3). Alteration and frag- direct forest structural alteration (including forest conversion, tim- mentation of forest landscapes compromise their ecosystem functions, in- ber extraction, and indirect effects, such as human-ignited fires) and cluding loss of biological diversity and reduction of carbon storage (4, 5). the resulting fragmentation of the remaining forest landscapes due Forest wildlands, those forests least affected by human activity, to such changes. Satellite data provide the most feasible solution for have the highest conservation value in terms of the range of ecosystem recurrent global mapping and monitoring of human-caused forest services they provide (6–10). These areas are often irreplaceable in alteration and fragmentation (16). harboring biological diversity, stabilizing terrestrial carbon storage, We define an intact forest landscape (IFL) as a seamless mosaic of regulating hydrological regimes, and providing other ecosystem forests and associated natural treeless ecosystems that exhibit no remote- functions (11). Their ability to perform ecosystem functions and their ly detected signs of human activity or habitat fragmentation and are resilience to natural disturbance and climate change are functions of large enough to maintain all native biological diversity, including viable their size. Many “umbrella” mammal and bird species, whose conser- populations of wide-ranging species (15). The global IFL mapping is vation also may enhance the protection of co-occurring species, re- based on a set of clear and straightforward criteria, designed to enable quire large natural habitats to survive (12). Large forest wildlands satellite-based mapping (see Materials and Methods). The term “intact are the greatest terrestrial carbon stores, a function at risk from forest forest landscape” is not congruent with the term “primary forest” as conversion (deforestation) and degradation (10). Small forest areas, defined by the Food and Agriculture Organization of the United even if pristine, have less potential for preserving wide-range species Nations (FAO) (17), and the two must not be confused. Primary forests populations and have lower resilience to natural disturbance and are part of IFLs, which also include nonforest intact ecosystems where effects of climate change (4). Hence, thesizeof the wildland matters: climatic, soil, or hydrological conditions prevent tree growth, tempo- the larger the size, the higher the conservation value of the territory. rally treeless areas after the natural disturbance (for example, wildfires), Preservation of forest wildlands requires a robust mapping and and water bodies. IFLs may also include areas affected by low-intensity monitoring system that can be implemented at national to global and historic human influence, such as hunting, scattered small-scale shifting cultivation, and preindustrial selective logging. IFLs include 1 2 large fragments of primary forests with a minimum extent of 500 km , University of Maryland, College Park, MD 20740, USA. Laestadius Consulting LLC, 3 4 Silver Spring, MD 20901, USA. Greenpeace Russia, Moscow, Russia. Greenpeace while smaller fragments of primary forests may be found outside IFLs. Germany, Hamburg, Germany. Global Forest Watch Canada, Ottawa, Ontario, Here, we use the archive of Landsat satellite imagery to map the global 6 7 Canada. World Resources Institute, Washington, DC 20002, USA. NGO Transpar- extent of IFLs in the years 2000 and 2013, to locate changes due to ent World, Moscow, Russia. *Corresponding author. Email: potapov@umd.edu alteration and fragmentation, and to identify causes of change. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 1of13 | SCIENCE ADVANCES RESEARCH ARTICLE RESULTS retaining more than 40% of their respective forest zone as IFLs in the We assessed the distribution and dynamics of IFLs within the ex- year 2000. tent of present-day forest ecosystems. We defined “forest” as lands Globally, 30% of the world forest area (land with tree canopy cover with a tree canopy cover greater than 20% in the year 2000, using a of 20% or greater) was within IFLs in the year 2000. Most of the IFL global tree canopy cover data set (18) as a reference. The present- area (82.3%) is covered with forest. The rest is covered with intact day extent of forest landscapes (mosaics of forests, naturally treeless treeless ecosystems (montane grasslands, treeless wetlands, and ecosystems, and deforested areas) is referred to as the “forest zone.” burned areas as a consequence of wildfires) and a small fraction of The forest zone extends over 58 million km , or 44% of Earth’s ice- nonvegetated areas (water, rocks, and ice). free land area. The extent of IFLs in the year 2000 totaled 12.8 mil- From 2000 to 2013, the global IFL area decreased by 7.2%, a reduc- 2 2 lion km , or 22% of the forest zone area. tion of 919,000 km (Table 1). Tropical regions are responsible for 60% The IFLs form distinctive regional groupings (Fig. 1 and Table 1), of the total reduction of IFL area. In particular, tropical South America 2 2 each with a unique history of alteration and fragmentation. In the hu- lost 322,000 km of IFL area, whereas Africa lost 101,000 km .Tempe- mid tropics, IFLs are found in the Amazon and Congo River basins, rate and southern boreal regions contributed 21% to the global IFL area the islands of Borneo and New Guinea, and the Southeast Asian high- loss. Northern Eurasia alone lost 112,000 km of its IFL area. The re- lands. Tropical regions comprise 48% of the total global IFL area. In maining 19% of IFL area reduction occurred within the northern boreal dry tropical and subtropical regions, IFLs are scarce or absent due to forests of Eurasia and North America. Compared to the year 2000 IFL extensive conversions to agriculture, some of which happened many extent, the proportion of the IFL area reduction was lowest in the north- centuries ago. Within the temperate and southern boreal forests of ern boreal regions and in the temperate forests of South America and North America and Eurasia, IFLs remain only in small areas spared highest in Australia, Southeast Asia, Africa, and the temperate regions from commercial logging and agriculture. IFLs are abundant in north- of North America and Eurasia (Fig. 2). ern boreal forests, interrupted mainly by mining, extraction of fossil Three countries comprise 52% of the total reduction of IFL area: 2 2 fuels, and human-ignited wildfires associated with roads. Northern Russia (179,000 km of IFL area lost), Brazil (157,000 km ), and Canada boreal IFLs comprise 36% of the total global IFL area. (142,000 km ). Proportional to the year 2000 IFL area, the highest per- IFLs were found within 65 countries in the year 2000 (Table 2). centages of IFL area reduction were found in Romania, which lost all Three countries (Russia, Brazil, and Canada) account for nearly IFLs,and Paraguay,where 79% of IFL area was lost; Laos, Equatorial two-thirds of the global IFL area. These countries are followed by Guinea, Cambodia, and Nicaragua each lost more than 35% of their IFL the Democratic Republic of the Congo, Peru, the United States (pri- area (Fig. 3 and Table 2). Assuming that the loss of IFLs continues at marily Alaska), Indonesia, Colombia, and Venezuela, each con- the average rate between 2000 and 2013, Paraguay, Laos, Cambodia, tributing more than 2% to the global IFL area. French Guiana has and Equatorial Guinea will lose their entire IFL area during the next the highest proportion of intactness of all countries, with IFLs making 20 years. Another 15 countries will lose all IFLs within a 60-year period, up 79% of the forest zone. This country is followed by Suriname, including such IFL-rich nations as the Republic of the Congo, Gabon, Guyana, Peru, Canada, Gabon, and the Republic of the Congo, each Cameroon, Bolivia, and Myanmar. Fig. 1. The world’s IFLs. IFL extent for the year 2013, IFL area reduction from 2000 to 2013, and boundaries of geographic regions used for the analysis. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 2of13 | SCIENCE ADVANCES RESEARCH ARTICLE Table 1. IFL extent and area reduction per geographic region. IFL area IFL proportion *Forest IFL proportion Forest IFL IFL area reduction Geographic IFL 2000 area of the forest proportion of global IFL zone area 2013 area reduction 2000–2013, 2 6 region (km ×10 ) zone in within IFL area in 2 6 2 6 (km ×10 ) (km ×10 ) 2000–2013 (%) not attributed 2000 (%) 2000 (%) 2000 (%) to fire (%) Africa 9.08 1.00 11.0 99.8 7.8 0.90 10.1 10.1 Australia 1.01 0.13 12.4 55.6 1.0 0.10 21.9 15.3 South America, temperate 0.41 0.16 38.2 43.4 1.2 0.15 1.3 0.9 South America, tropical 14.70 4.43 30.1 98.9 34.6 4.11 7.3 7.1 North America, temperate 5.85 0.54 9.2 66.5 4.2 0.46 15.5 11.2 and southern boreal North America, 3.89 3.04 78.2 63.8 23.7 2.94 3.3 0.3 northern boreal Northern Eurasia, temperate and 11.96 1.23 10.3 69.8 9.6 1.12 9.1 7.4 southern boreal Northern Eurasia, 3.33 1.57 47.0 75.7 12.2 1.50 4.4 1.8 northern boreal Southeast Asia 7.38 0.72 9.8 93.7 5.6 0.62 13.9 13.9 World total 57.60 12.81 22.2 82.3 100.0 11.89 7.2 5.7 *Forest is defined here as land with tree canopy cover above 25%, as depicted by the global tree cover product (18). from infrastructure and logging sites (21.2%). Other causes includ- ed fragmentation by roads for mining and oil/gas extraction, pipe- lines, and power lines (12.1%) and expansion of the transportation road network (2.0%). At the regional level, we observed a diversity of leading IFL area reduction causes (Fig. 4 and Table 3), whereas for each particular region, a single cause accounted for more than 50% of the regional IFL area reduction. Using sample-based analysis and the annual forest loss data set (18), we found that 14% of the total IFL area reduction was due to direct alteration caused by logging, clearing, and fires. The remaining 86% was due to fragmentation by such disturbances and construction of infrastructure. The annual forest loss within IFLs may be used as a proxy to understand the temporal dynamics of IFL area reduction. In tropical regions, the annual forest loss within IFLs increased during the past 13 years (Fig. 5). The average annual forest loss within IFL reduction area for the 2011–2013 period was triple the average for the 2001–2003 period for each of the three tropical regions, with the high- est increase observed in central Africa. Of the total IFL area in the year 2000, 12.4% fell within protected Fig. 2. Distribution of IFL area in the year 2000 and reduction of IFL area areas (PAs), with a management regime consistent with the Interna- 2000–2013 by geographic region. The y axis shows the initial IFL proportion tional Union for Conservation of Nature (IUCN) categories I to III of the forest zone in the year 2000. The x axis shows the reduction in IFL area (19). Australia and temperate South America have the largest propor- from 2000 to 2013 as the proportion of IFL 2000 area. The area of each bubble tion of IFLs under legal protection (47.4 and 43.7%, respectively), 2 6 indicates the IFL area in km ×10 . Values within each bubble represent the re- whereas temperate and southern boreal northern Eurasia (7.7%) gional IFL area in the year 2000 as a percent of the global total. and northern boreal regions (7.7% in North America and 5.2% in Eur- asia) have the lowest. Forty of the 65 countries, in which IFLs were We used stratified sampling to identify the primary causes of the present in the year 2000, had at least 10% of the IFL area under legal IFL area reduction. At the global level, the leading fragmentation protection. Uganda, the Dominican Republic, Thailand, and Cuba had and alteration agents were timber harvesting (37.0% of global IFL protected more than 90% of their IFL area. Some countries do not in- area reduction), agricultural expansion (27.7%), and wildfire spread clude any IFLs within category I to III PAs, including many Southeast Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 3of13 | SCIENCE ADVANCES RESEARCH ARTICLE Table 2. IFL extent and area reduction per country. IFL area IFL proportion IFL proportion IFL area reduction Country code IFL 2000 of the forest of global IFL Country name reduction 2000–2013, 2 3 (for Fig. 3) area (km ×10 ) zone in area in 2000–2013 (%) not attributed 2000 (%) 2000 (%) to fire (%) Angola AGO 2.9 0.3 0.02 13.7 13.7 Argentina ARG 39.9 6.5 0.3 2.0 1.8 Australia AUS 82.2 9.8 0.6 32.7 22.8 Belize BLZ 4.3 19.7 0.03 4.8 4.8 Bhutan BTN 6.4 19.3 0.05 15.5 15.5 Bolivia BOL 233.3 28.9 1.8 19.6 18.3 Brazil BRA 2476.1 31.7 19.3 6.3 6.2 Brunei BRN 2.0 35.1 0.02 17.0 17.0 Cambodia KHM 1.1 0.9 0.01 38.2 38.2 Cameroon CMR 52.8 13.4 0.4 25.2 25.2 Canada CAN 3040.3 51.0 23.7 4.7 2.3 Central African Republic CAF 8.7 1.5 0.1 34.4 34.4 Chile CHL 131.4 36.9 1.0 1.3 0.9 China CHN 45.0 1.6 0.4 11.5 11.2 Colombia COL 349.2 31.0 2.7 1.3 1.3 Costa Rica CRI 3.2 6.2 0.02 3.0 3.0 Côte d’Ivoire CIV 4.6 1.7 0.04 17.5 17.5 Cuba CUB 0.5 0.5 0.004 0 0 Democratic Republic COD 643.9 27.7 5.0 4.2 4.2 of the Congo Dominican Republic DOM 0.8 1.7 0.01 29.0 1.6 Ecuador ECU 53.3 22.3 0.4 5.3 5.3 Equatorial Guinea GNQ 4.2 15.8 0.03 45.2 45.2 Ethiopia ETH 3.7 1.4 0.03 9.6 9.6 Finland FIN 9.7 3.1 0.1 0.2 0.2 French Guiana GUF 65.4 79.1 0.5 5.7 5.7 Gabon GAB 108.8 41.2 0.8 22.9 22.9 Georgia GEO 9.0 18.3 0.1 0.7 0.7 Guatemala GTM 5.7 5.2 0.04 13.3 13.3 Guyana GUY 144.1 69.6 1.1 11.3 11.3 Honduras HND 6.7 6.0 0.1 28.6 28.6 India IND 33.7 5.6 0.3 1.6 1.6 Indonesia IDN 359.2 20.1 2.8 10.8 10.8 Japan JPN 1.2 0.4 0.01 0.01 0.01 continued on next page Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 4of13 | SCIENCE ADVANCES RESEARCH ARTICLE IFL area IFL proportion IFL proportion IFL area reduction Country code IFL 2000 of the forest of global IFL Country name reduction 2000–2013, 2 3 (for Fig. 3) area (km ×10 ) zone in area in 2000–2013 (%) not attributed 2000 (%) 2000 (%) to fire (%) Kazakhstan KAZ 4.4 16.6 0.03 2.3 2.3 Laos LAO 8.5 3.8 0.1 47.9 47.9 Liberia LBR 4.7 5.0 0.04 32.2 32.2 Madagascar MDG 17.2 7.2 0.1 19.0 18.5 Malaysia MYS 21.1 6.5 0.2 25.1 25.1 Mexico MEX 15.0 1.8 0.1 2.8 2.6 Mongolia MNG 11.7 12.6 0.1 12.5 0.4 Myanmar MMR 52.9 10.1 0.4 30.9 30.9 Nepal NPL 0.6 0.6 0.004 0 0 New Zealand NZL 43.1 25.4 0.3 1.3 1.2 Nicaragua NIC 10.3 8.0 0.1 38.1 38.1 Nigeria NGA 3.0 1.3 0.02 5.3 5.3 Norway NOR 1.8 1.4 0.01 1.0 1.0 Panama PAN 14.5 19.6 0.1 19.8 19.8 Papua New Guinea PNG 159.8 35.1 1.2 13.3 13.3 Paraguay PRY 44.5 11.1 0.3 79.3 79.3 Peru PER 567.2 68.5 4.4 6.1 6.1 Philippines PHL 4.0 1.6 0.03 9.5 9.5 Republic of the Congo COG 138.7 40.7 1.1 17.7 17.7 Romania ROU 1.0 0.6 0.01 100.0 100.0 Russia RUS 2744.3 28.3 21.4 6.5 4.3 Samoa WSM 0.7 23.8 0.01 0.6 0.6 Solomon Islands SLB 7.8 32.3 0.1 52.9 52.9 Suriname SUR 107.4 73.8 0.8 5.7 5.7 Sweden SWE 11.6 3.0 0.1 0.8 0.8 Tanzania TZA 4.1 0.8 0.03 2.3 2.3 Thailand THA 19.4 7.0 0.2 7.8 7.8 Uganda UGA 1.0 0.7 0.01 0.9 0.9 United States USA 539.3 14.2 4.2 7.9 0.2 Vanuatu VUT 0.7 7.5 0.01 1.1 1.1 Venezuela VEN 312.8 35.7 2.4 1.5 1.5 Vietnam VNM 4.1 1.7 0.03 25.5 25.5 Asian countries (Lao People’s Democratic Republic, Vietnam, Cambodia, IFL area reduction (Table 4). In Africa, North America, and Eurasia, and Philippines), Papua New Guinea, Ethiopia, Angola, and Nicaragua. the reduction of IFL area was more than 4 times higher outside PAs Using matching sampling analysis, we found that the reduction than inside PAs, whereas it was 2.6 times higher in Southeast Asia and of IFL area for reasons other than fire was 3.4 times higher outside almost double in tropical South America. PAs (6.2%) than within PAs (1.8%). We found a large difference in To study the effect of legal protection and voluntary forest man- most regions between protected and unprotected areas in terms of agement certification on IFL area reduction by logging, we analyzed Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 5of13 | SCIENCE ADVANCES RESEARCH ARTICLE Fig. 3. Distribution of IFLs by country in the year 2000 and reduction of IFL area 2000–2013. The y axis shows the IFL area in the year 2000. The x axis shows the reduction in IFL area from 2000 to 2013 as the proportion of IFL 2000 area. Country codes are given in Table 2. PAs and timber concessions in the three central African countries, Expansion of logging into intact forest areas has many direct where up-to-date spatial information on forest management exists: effects on ecosystem functions, including reduction of carbon stor- Cameroon, Gabon, and the Republic of the Congo. Some of the con- age (20), decrease of habitat suitability (6, 21), and increase of vul- cessions were certified to the Forest Stewardship Council (FSC) stan- nerability to human-induced wildfires (22, 23). Fragmentation of dard. Certified concessions had thesameorhigherproportionofIFL forest landscapes by logging and logging roads causes direct habitat area reduction than noncertified concessions, whereas the IFL area loss (24) and increases the incidence of poaching (25), resulting in loss wasatleast four timeslower in PAsthanintimber concessions species loss. Even within areas designated for sustainable forest (Table 5). management, like some tropical timber concessions, the construc- tion of new logging roads initiates a cascade of land use changes and subsequent reduction in landscape conservation value. The ex- DISCUSSION ample from the Republic of the Congo (Fig. 6) shows how expan- Causes of IFL area reduction sion of logging infrastructure and a new hydropower project have Industrial timber extraction, resulting in forest landscape alteration and markedly reduced IFL area. Agricultural expansion, forest fires, and fragmentation, was the primary global cause of IFL area reduction. In the potential increase of unregulated hunting (26) are coincident Africa and Southeast Asia, selective logging was the dominant IFL loss with the expansion of the logging road network. cause (77 and 75% of the total loss of IFL area, respectively), whereas Agricultural expansion was the second most important cause of clear-cutting was the main IFL loss cause in the temperate and southern IFL area reduction. In tropical South America, expansion of agri- boreal regions of North America and Eurasia (68 and 54%, respective- culture overall and of pastures in particular contributed 65 and ly). Therelativeproportion of forest loss and fragmentation within IFL 53% of the overall IFL area loss, respectively. Expansion of indus- reduction area depends on the logging method and the intensity of tim- trial crops (for example, soybean) was not detected as a cause of ber extraction. Clear-cuts caused a higher proportion of forest alteration IFL area reduction using our sample-based analysis. IFLs were (15% of the total IFL area reduction) compared to selective logging not directly affected by industrial crop expansion in South America (1.2%), with the remaining IFL reduction attributed to fragmentation because it mainly occurred in areas previously converted to pas- by logging sites and roads. Southeast Asia had a higher proportion of tures (27). In tropical Africa and Southeast Asia, slash-and-burn clearing within selectively logged areas than tropical Africa and South smallholder agricultural expansion contributed 23 and 15%, respec- America (1.4 versus 0.3% for each of the latter). tively, to the total IFL area reduction. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 6of13 | SCIENCE ADVANCES RESEARCH ARTICLE Establishment of oil palm plantations contributed 0.2% of the Forest fires associated with infrastructure and therefore assumed to total IFL area reduction. We found new oil palm plantations be human-induced accounted for 21% of the total IFL area reduction. affecting IFLs in all tropical regions (Fig. 7). Plantations usually fol- Fire-related degradationwas foundwithinall regionsexceptSoutheast low selective logging expansion and represent an example of how Asia. The absence of fires as an IFL degradation cause in Indonesia is industrial logging operations can set off a cascade of interventions explained by the fact that the remaining IFLs are located within that eventually result in the final conversion of natural forests to remote mountain areas, whereas fires are much more prevalent in industrial monoculture plantations (28). fragmented and degraded lowland forests. Fire was the main cause 2 3 Fig. 4. Regional reduction of IFL area (km ×10 ) and causes of change. Table 3. Sample-based assessment of the causes of IFL area reduction. 2 3 2 3 The IFL area reduction by proximate cause, km ×10 (standard error, km ×10 ) Total IFL Number Mining, oil area reduction of samples Timber Agriculture and Other transportation, 2 3 2 Wildfire and gas, (km ×10 ) (1 km each) harvesting pasture expansion tourism hydropower Africa 101.3 100 0 77.5 (0.4) 22.8 (0.4) 0 1.0 (0.1) Australia 27.4 50 6.6 (0.2) 0 0.5 (0.1) 17.6 (0.2) 2.7 (0.1) South America, 2.1 50 0.5 (0.01) 0.9 (0.01) 0 0 0.7 (0.01) temperate South America, 321.5 300 7.5 (0.3) 68.1 (0.8) 209.0 (0.9) 28.4 (0.5) 8.6 (0.3) tropical North America, temperate and 83.3 84 24.8 (0.4) 56.6 (0.4) 0 1.0 (0.1) 1.0 (0.1) southern boreal North America, 101.2 116 92.5 (0.3) 0 0 8.7 (0.3) 0 northern boreal Northern Eurasia, temperate and 112.1 113 23.8 (0.4) 60.0 (0.5) 0 26.3 (0.4) 2.0 (0.1) southern boreal Northern Eurasia, 69.5 87 39.2 (0.4) 1.6 (0.1) 0 28.8 (0.4) 0 northern boreal Southeast Asia 100.2 100 0 75.6 (0.4) 22.6 (0.4) 0 2.0 (0.1) Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 7of13 | SCIENCE ADVANCES RESEARCH ARTICLE of IFL area reduction in northern boreal regions (91% in North of disturbance. The highest percent of forest clearing was observed for America and 56% in northern Eurasia) and accounted for more than oil palm plantation establishment (43% of the total IFL area reduction) 20% of IFL reduction in temperate North America, temperate Eurasia, and forest fires (41%), followed by clear-cut logging (15%), pasture and Australia. Excluding fires as a cause of IFL degradation would (15%), and other agricultural expansion (8%). However, the core areas change the global IFL area reduction from 7.2 to 5.7% (Table 1) but of IFL also experience natural forest loss events. Intact landscapes are would not lead to notable changes in the ranking of regions by the not static in terms of land cover change. Large-scale wildfires, pest proportion of IFL area lost. attacks, and wind damage occur naturally in many temperate and bo- Energy production (oil and gas extraction and hydropower) and real forests, where they are followed by natural regeneration. Accord- mining operations are globally important causes of IFL area reduction ing to the global forest cover loss product (18), the total area of forest due to the fragmenting effect of their transportation infrastructure. Oil loss within IFL from 2001 to 2013 was 314,000 km ,or2.5%ofthe and gas extraction was the leading fragmentation cause in northern IFL area. This includes both anthropogenic and natural disturbances. Eurasia (specifically in the Russian Federation), accounting for 41% The IFL 2000–2013 change data set shows that 55% of the total forest of IFL reduction in the northern boreal and 23% in the southern bo- loss area fell within stable IFL areas and was therefore assumed to repre- real and temperate forests. Russia is the largest producer of crude oil sent natural ecosystem dynamics. However, for the tropical regions, the and the second largest producer of natural gas in the world. Recent proportion of natural disturbance within IFLs was small (8.6% of the expansion of oil and gas exploration and extraction in East Siberia total forest loss area within year 2000 IFLs). caused fragmentation of the forest wildlands through establishment of new pipelines and extraction infrastructure, usually accompanied Legal protection of IFLs by logging and human-ignited fires. Mining and mineral exploration In all regions, the proportion of the reduction of IFL area was lower (mostly for gold) played a significant role in Australia (64% of the total inside of PAs than outside of PAs (Table 4), suggesting that legal IFL reduction) and tropical South America (9%). protection was effective in preventing IFL loss. However, this con- Fragmentation generally dominatesoverforestclearingasafactor clusion may be invalid due to the nonrandom distribution of PAs of IFL area reduction. Their relative contribution depends on the type within IFL areas (29). To control for the varying vulnerability of IFLs to human alteration and fragmentation, we implemented a sample matching method to account for the nonrandom distribution of PAs. The results confirmed that legal protection has been effective at lessening the reduction of IFL areainall regionsexceptAustralia (where roads have been constructed near PA boundaries) and tempe- rate South America (where new tourist infrastructure has been devel- oped in a national park). However,when analyzing thecausesofIFL area reduction, we noticed that legal protection was not always an ef- fective way to limit agricultural expansion. Of the 10 PAs in Africa, classified as IUCN categories I and II that experienced more than 1% IFL area loss, 7 were subjected to smallholder agricultural expan- sion. Two of these PAs are in Andasibe-Mantadia National Park (in which all IFLs disappeared) and Tsaratanana Strict Nature Reserve Fig. 5. Annual proportion of the total forest loss within tropical forests that (in which 28% of the IFL area was lost). In both cases, slash-and-burn lost IFL status between 2000 and 2013. agriculture expanded within park boundaries. The same process was Table 4. IFL area reduction inside and outside IUCN category I to III PAs. Area-based estimate represents area calculated from the map. Sample-based estimate is based on matching sampling analysis performed only within portions of IFLs vulnerable for degradation. This analysis only considers the reduction of IFL area 2000–2013 that was not attributed to fire. Area-based estimate Sample-based estimate and standard error (SE) IFL 2000 within Region IFL area reduction IFL area reduction IFL area reduction IFL area reduction IUCN category within PAs (%) outside PAs (%) within PAs, % (SE, %) outside PAs, % (SE, %) I–III PAs (%) Africa 10.8 1.6 11.2 5.5 (0.72) 25 (1.37) Australia and New Zealand 47.4 9.6 20.5 54.6 (1.57) 44.1 (1.57) Temperate South America 43.7 0.4 1.3 1.6 (0.40) 1.1 (0.33) Tropical South America 15.1 2.0 8.0 8.0 (0.86) 14.6 (1.12) Temperate North America 34.0 1.1 16.4 5.2 (0.70) 24.6 (1.36) Temperate Northern Eurasia 7.7 1.4 7.9 3.2 (0.56) 17.5 (1.20) Southeast Asia 12.7 4.6 15.2 6.8 (0.80) 17.9 (1.21) Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 8of13 | SCIENCE ADVANCES RESEARCH ARTICLE observed in Virunga National Park (Democratic Republic of the IFL area reduction worldwide. Standards for responsible forest Congo), which lost 3.3% of its IFL area due to agricultural expansion. management, including those of the FSC, seek to balance forest- Another cause of IFL area reduction within PAs is the development based economic development with conservation. FSC regards IFLs of new infrastructure. In some cases, new transportation infrastructure as a type of high conservation value forest, and the FSC standard causes fragmentation, as in Domogled-Valea Cernei National Park states that their degradation should be avoided. In 2014, the General (Romania). In other cases, the development of infrastructure for Assembly of FSC adopted a motion (Motion 65) that calls upon FSC tourism and recreation caused IFL area reduction, for example, the ex- to do the following: “within IFL cores ensure that Certificate Holders pansion of the road network in Puyehue National Park (Chile) and the implement protection measures (for example, set-asides, legal construction of a ski resort within Sochinsky National Park (Russia). protected areas, conservation reserves, deferrals, community reserves, Although some of these infrastructure projects were developed to in- indigenous protected areas etc.) ensuring management for intactness” crease PA income and stimulate public awareness of the importance of (30). If Motion 65 is implemented, we should, at least, in the future, nature conservation, they nevertheless had the effect of reducing the expect IFL fragmentation to proceed more slowly within FSC-certified extent of remaining forest wildlands through fragmentation. concessions than in noncertified concessions. Our results from the Many IFLs contain high-value timber resources, and logging period 2000–2013 suggest that the pace of IFL fragmentation due and associated fragmentation by roads are the leading causes of to selective logging in central Africa is faster within FSC-certified Table 5. IFL extent and area reduction within logging concessions in three central African countries. The spatial database of logging concessions in Cameroon (2013), Republic of the Congo (2013), and Gabon (2012) was obtained from the World Resources Institute (www.wri.org/our-work/project/congo- basin-forest-atlases). IFL area IFL area IFL area IFL area IFL proportion IFL proportion reduction reduction reduction reduction of FSC-certified Country of total concession 2000–2013 2000–2013 2000–2013 2000–2013 concession area area in 2000 (%) within the within all within FSC-certified within PAs in 2000 (%) country (%) concessions (%) concessions (%) (IUCN category I–III) (%) Cameroon 40.5 38.4 25.2 41.1 84.5 0.3 Republic of the Congo 42.4 61.6 17.7 37.1 41.9 4.8 Gabon 48.4 29.7 22.9 37.9 37.0 9.0 Fig. 6. Stages and causes of the IFL area reduction and landscape transformation in the Republic of the Congo (map center at 16°0′E1°12′N). The infrastructure and IFL extent within the area are shown as of September 2016. The map shows expansion of settlements and regional transportation and logging roads from the year 2000 until 2016. Logging road expansion caused the reduction of IFL area. IFL extent was mapped for the years 2000, 2013, and 2016. New settlements and agricultural areas appeared along existing and established roads. Logging expansion triggered forest fires that initiated from the roads and forest clearings. In September 2016, a water reservoir was constructed within the remaining IFL area, which caused continuous fragmentation and transformation of the surrounding landscape. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 9of13 | SCIENCE ADVANCES RESEARCH ARTICLE Fig. 7. Examples of the ongoing expansion of oil palm plantations within IFLs in tropical regions. Each example shows IFL degradation depicted in year 2015 or 2016 cloud-free Landsat-8 satellite images. All maps have the same scale. The IFL boundary in 2013 is marked by a yellow line, and the IFL boundary for the year 2000 is marked by a red line. Oil palm plantations established before the year 2013 are denoted as “A,” and plantations established after 2013 are denoted as “B”. (1) Gabon; image subset centered at 11°47′E 2°7′N; image date, 12 January 2015. (2) Indonesia; subset centered at 139°45′E 7°21′S; image date, 10 May 2016. (3) Peru; subset centered at 75°7′W 8°15′S; image date, 24 June 2016. concessions than outside them, due to selective logging and fragmen- portation infrastructure, agricultural areas, and logging sites were as- tation by logging road construction (Table 5). By definition, selective sumed to be caused by humans and thus were treated as an IFL logging and establishment of associated infrastructure in an IFL re- reduction factor. Although lightning strikes can ignite forest fires, sev- duce its area. Although we do not know the degree to which IFL frag- eral studies have found that most fires in the vicinity of infrastructure mentation is actively avoided by logging operations, it is evident that and logging sites are of human origin, in boreal (22, 34)aswell asin selective logging within FSC-certified concessions is a significant temperate (35, 36)and tropical forests(37). However, large fires may driver of IFL area reduction in central Africa. For other regions, suf- be of natural origin even if colocated with infrastructure (38, 39). Our ficiently detailed spatial information on logging concessions and cer- approach has been to construct a set of mapping rules that can be tification is largely unavailable, precluding similar analysis. applied consistently at the global scale. For burned areas, our rule as- sumes that fires in the vicinity of areas with human access are likely to Regional approaches to IFL monitoring have a human cause. Regional conservation specialists (40)havechal- National projects focused on characterizing “primary forests,”“high lenged the utility of applying globally consistent criteria at regional conservation value forests,” or “wilderness areas” are complementary scales, specifically in interpreting the causes of fires in boreal Canada. to the global IFL mapping initiative. Such maps often provide In response to these concerns, our global analysis differentiates IFL information on smaller fragments of high conservation value forests reduction due to fire from other causes. located outside of the largest wilderness areas. The work of Global The IFL concept is defined to map the large unfragmented tracts of Forest Watch Canada (GFWC) represents an example of regional primary forests. A different set of criteria, using a smaller threshold for IFL mapping that uses different criteria from our global method. minimum patch size, would be needed to map small fragments of GFWC criteria allow for inclusion of all burned areas within IFLs, re- primary forest. Our earlier work in central Africa and insular South- gardless of the cause of fire, and require a smaller minimum area for a east Asia showed that substantial areas of primary forests exist outside patch to qualify as an IFL (31, 32). The GFWC IFL map has been of IFLs. We found that 38.6% of the primary forest area in the Dem- updated for the year 2013 (33), allowing for a comparison of regional ocraticRepublicofthe Congo(41) is located outside of IFLs, whereas and global IFL maps. The GFWC map for 2013 showed that Canada on the island of Sumatra, Indonesia, the proportion is 73.2% (28). The has a total IFL area that is 1.4 times larger than the one shown in our method presented here can be used to identify conservation priority global map. However, 98.6% of the intact area from our global map is areas at the regional and national levels if the criteria for minimum included in the GFWC map, illustrating agreement on the location eligible patch size and alteration are adjusted for this purpose. and extent of core wilderness areas. The standard method presented in this paper is capable of Accuracy of the global IFL map providing a globally consistent characterization of the extent of IFLs To assess the accuracy of the IFL 2000–2013 change map, we used the and its change over time. However, for regional mapping initiatives, same 1000 random samples that were used to assess the causes of IFL regional relevance may be a higher priority than global consistency. area reduction. The samples were interpreted separately from the gen- Regional assessments may wish to deviate from the standard global eration of the map. The sampling design made it possible to estimate method by using criteria that are adapted to the regional context, as commission error (that is, change that had been falsely attributed to GFWC does. It is important to be clear on the differences in criteria as human causes) but not omission error (human-caused change that they may explain a major part of the seeming discrepancy between a had been overlooked, that is, that was not reflected in the change regional and a global map. map). Visual interpretation of Landsat imagery and of high-resolution An important difference between the global IFL assessment imagery available through Google Earth confirmed that 92% of the presented here and the regional IFL assessment produced by GFWC sampled area of IFL area reduction had been correctly classified. It is the treatment of fire-related disturbances. It is typically not possible was not possible to confirm whether the alterations for the remaining to determine whether a fire had a natural origin or was caused by sampled area (8%) were human-caused based on Landsat or high spa- people. In the global assessment, burned areas in the vicinity of trans- tial resolution satellite imagery. Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 10 of 13 | SCIENCE ADVANCES RESEARCH ARTICLE A partial field validation of the IFL 2000 map by Greenpeace in Hawaii in 2016 adopted a motion (Motion 048) that “encourages Russia and GFWC (42, 43) confirmed that intact areas within the states, the private sector and international financial institutions to: a. boreal and temperate forests of European Russia and Canada had avoid loss and degradation of primary forests, including intact forest been correctly classified. An alternative approach to validation focused landscapes;b.promote conservation of primary forests, including in- on forest structure to differentiate intact forests from forests within tact forest landscapes” (51). National approaches to protecting IFLs degraded or altered landscapes. Studies by Margono et al. (28)and include expansion of the PA network and the establishment of a sys- Zhuravleva et al. (41) used data from the Geoscience Laser Altimeter tem for wilderness area management similar to that of the United System to examinethe tree canopy structureinsideand outsideofIFLs States (52). Large forested wildlands often straddle international in Sumatra (Indonesia) and the Democratic Republic of the Congo. Their boundaries, highlighting the need for effective international conserva- results revealed a statistically significant difference in average forest tion strategies (10). IFLs provide a framework for maintaining large, height between intact forests and other forests (fragmented and altered). contiguous, and often transnational blocks of forest wildlands. The high carbon stocks found within IFLs illustrate their potential benefit IFL role in climate change mitigation to climate change mitigation strategies. This study has demonstrated The primary forests that remain within IFLs represent the most signif- that legal protection is an effective policy for reducing the degradation icant carbon pool within the tropical biome (44). Using a benchmark of IFLs. We suggest that IFLs should be considered when existing PA tropical forest carbon map produced for the early 2000s (45), we networks are revised and expanded. We also suggest that monitoring estimate that the total biomass carbon pool in the tropical forest zone of forest intactness should be treated as an important aspect of nation- was 243 Gt C around year 2000, of which IFLs stored 97 Gt C (40%). al and global forest assessments. The average carbon density was greater in IFLs than in the rest of the tropical forest zone: 3.7 times higher in Africa, 3.4 times higher in South America, and 1.7 times higher in Southeast Asia. MATERIALS AND METHODS IFLs in the boreal and temperate regions differ from those in the The extent of the forest zone was mapped using the global year 2000 tropics by having lower biomass per unit area and lower produc- tree canopy cover data set (18) with a 20% tree canopy cover thresh- tivity than managed forests. In the year 2000, the average growing old. Inland water bodies and naturally treeless ecosystems were includ- stock in North America and Eurasia was 1.4 times higher in forests ed in the forest zone. Fragments of land in the forest zone with a 3 3 2 outside IFLs (145.5 m /ha) than within IFLs (103.1 m /ha) (46). This contiguous area smaller than 500 km were excluded from consider- has historical reasons. In the past, temperate and southern boreal ation. Geographic regions within the forest zone (Fig. 1) were delineated forests have been cleared, converted into managed forests, or fragmen- using natural boundaries between forested areas. The boundary be- ted by infrastructure, leaving mostly low productivity forests (specifi- tween northern boreal and southern boreal/temperate regions in cally, peatlands and mountains) as IFLs (42). Nevertheless, the vast North America and northern Eurasia was based on Landsat data areas of boreal IFLs represent a large and relatively stable above- analysis and represents the de facto dividing line between lands that and belowground carbon storage that plays an important role in the have, and have not, been subjected to industrial logging as of the global climate system. Although the recent increase in boreal wildfire year 2013. frequency and intensity (39) threatens long-term aboveground carbon An IFL is defined as a seamless mosaic of forests and asso- storage in northern forests, it has been shown that IFLs have a lower ciated natural treeless ecosystems that exhibit no remotely de- fire frequency compared to fragmented and developed areas (22). Per- tected signs of human activity or habitat fragmentation and is mafrost protection is another important IFL function. Road and large enough to maintain all native biodiversity, including viable pipeline constructions have multiple direct and indirect effects on populations of wide-ranging species (15). An IFL includes both permafrost, increasing its vulnerability to thawing (47). Almost 52% forest and naturally treeless ecosystems. Two main criteria were (2.6 million km ) of the total continuous and discontinuous perma- used to distinguish an IFL patch from the surrounding landscape: frost area within forest zone in North America and Eurasia is located (i) ecosystem alteration and (ii) landscape fragmentation by infra- within the remaining IFLs (48). structure and disturbance. Areas that have been altered or man- aged (through agriculture, logging, and mining) were excluded, along with a buffer zone of 1 km (53)oneithersideofinfra- CONCLUSIONS structure elements (roads, pipelines, power lines, and navigable Intactness is a good indicator of the comprehensive conservation value rivers). Past disturbances that occurred more than 30 to 70 years of a forest landscape (7, 8). It is related to specific ecosystem values, ago, scattered small-scale shifting cultivation, nonindustrial timber such as ecosystem integrity and resilience to natural disturbances and harvesting by indigenous forest dwellers, and low-intensity distur- to ongoing climate change. It is also related to other forest ecosystem bance not directly observable in remotely sensed data (hunting functions, such as biodiversity (49). It can be reduced very rapidly, in a and forest grazing) were not considered IFL alteration or frag- matter of months and years, by increased fragmentation and access, mentation factors. An IFL patch must have (i) a minimum size even without changes in tree canopy cover. On the other hand, intact- of 500 km , (ii) a minimum width of 10 km, and (iii) a minimum ness is hard to gain, at least within a short time span. That is why corridor/appendage width of 2 km. Any patch that falls below these intact landscapes should be treated as having high (or even the high- thresholds, for example, due to fragmentation, logging, or fire, was est) conservation value. The conservation value of an intact area is rejected in its entirety. dependent on its size because many umbrella mammal and bird spe- Source data for IFL mapping and monitoring were taken from cies require large natural habitats to survive (12, 50). That is why the the global archive of medium spatial resolution Landsat satellite size of the intact area should always be taken into consideration when imagery. We used a collection of single-date Landsat images (15)to assessing wildland conservation value. The Congress of the IUCN held map IFLs for the year 2000. Landsat images circa year 1990 were used Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 11 of 13 | SCIENCE ADVANCES RESEARCH ARTICLE 3. E. W. Sanderson, M. Jaiteh, M. A. Levy, K. H. Redford, A. V. Wannebo, G. 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Turetsky, Alaska’s changing fire regime—Implications remote sensing data interpretation specialists, Geographic Information Systems technicians, and for the vulnerability of its boreal forests. Can. J. For. Res. 40, 1313–1324 (2010). nature conservation experts who provided invaluable knowledge and assistance in the 40. P. Lee, Caution against using intact forest-landscapes data at regional scales. Ecol. Soc. 14, development and validation of the IFL data set. Funding: The IFL 2000–2013 global update was r1 (2009). funded by Greenpeace Russia and Global Forest Watch, an initiative of the World Resources 41. I. Zhuravleva, S. Turubanova, P. Potapov, M. Hansen, A. Tyukavina, S. Minnemeyer, Institute. Author contributions: A.Y., L.L., C.T., P.P., and S.T. designed the IFL concept. S.T., I.Z., N. Laporte, S. Goetz, F. Verbelen, C. Thies, Satellite-based primary forest degradation A.K., E.E., and P.P. performed global IFL change mapping. S.M. provided data and analysis of assessment in the Democratic Republic of the Congo, 2000–2010. Environ. Res. Lett. 8, FSC-certified concessions in central Africa. W.S. performed the national IFL mapping in Canada. 024034 (2013). P.P performed sample-based analysis of IFL change causes and effectiveness of legal protection. 42. A. Y. Yaroshenko, P. V. Potapov, S. A. Turubanova, The Last Intact Forest Landscapes of The manuscript was prepared by P.P., M.C.H., and L.L. with contributions from S.T., A.Y., C.T., S.M., Northern European Russia (Greenpeace Russia and Global Forest Watch, 2001). and W.S. Competing interests: The authors declare that they have no competing interests. 43. P. Lee, D. Aksenov, L. Laestadius, R. Nogueron, W. Smith, Canada’s Large Intact Forest Data and materials availability: The IFL extent and change maps in GIS format are available on Landscapes (Global Forest Watch Canada, 2003). the project website (www.intactforests.org/) and through the Global Forest Watch data portal 44. A. Tyukavina, A. Baccini, M. C. Hansen, P. V. Potapov, S. V. Stehman, R. A. Houghton, (www.globalforestwatch.org/). All tabular data needed to evaluate our conclusions are present in A. M. Krylov, S. Turubanova, S. J. Goetz, Aboveground carbon loss in natural the paper. Additional data related to this paper may be requested from the authors. and managed tropical forests from 2000 to 2012. Environ. Res. Lett. 10, 074002 (2015). Submitted 18 April 2016 45. S. S. Saatchi, N. L. Harris, S. Brown, M. Lefsky, E. T. A. Mitchard, W. Salas, B. R. Zutta, Accepted 29 November 2016 W. Buermann,S.L.Lewis,S.Hagen, S.Petrova, L. White, M. Silman,A.Morel, Benchmark Published 13 January 2017 map of forest carbon stocks in tropical regions across three continents. Proc. Natl. Acad. 10.1126/sciadv.1600821 Sci. U.S.A. 108, 9899–9904 (2011). 46. M. Santoro, C. Beer, O. Cartus, C. Schmullius, A. Shvidenko, I. McCallum, U. Wegmüller, Citation: P. Potapov, M. C. Hansen, L. Laestadius, S. Turubanova, A. Yaroshenko, C. Thies, A. Wiesmann, Retrieval of growing stock volume in boreal forest using hyper-temporal W. Smith, I. Zhuravleva, A. Komarova, S. Minnemeyer, E. Esipova, The last frontiers of series of Envisat ASAR ScanSAR backscatter measurements. Remote Sens. Environ. 115, wilderness: Tracking loss of intact forest landscapes from 2000 to 2013. Sci. Adv. 3, 490–507 (2011). e1600821 (2017). Potapov et al. Sci. Adv. 2017;3 : e1600821 13 January 2017 13 of 13

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