Abstract

202 BOOK REVIEWS plantations. A comparison between Figure 6.9 showing the percentage of land covered by trees at the end of the nineteenth century and Figure 7.6 showing land covered by trees at the end of the twentieth century reveals the increase in tree cover across the country during that period, driven by afforestation and natural regeneration. Chapter 7 sets out the threats to trees, both issues from the past and those of today. I was particularly pleased to see acknowledged the increased amount of dead wood in the landscape compared with the past, when all the wood and timber was utilised throughout society. Arbor- iculturalists are finding that in some instances the accumulation of dead wood can harbour pathogens. Another unobvious threat for farmland trees is the raised levels of inorganic nitro- gen which suppresses growth of mycorrhizal fungi on which tree health depends. Large scale tree epidemics such as Dutch elm disease in the 1970s and now ash chalaria, sudden oak decline (and potentially others) have only come about in the twentieth century, the result of climate change, and the physical movement of carriers. Trees in south-east England are cur- rently under pressure from lack of groundwater,