Tree health and the structure of rural tree populations in England, c.1550-2015
From Dutch elm disease to chestnut blight and ash dieback, it seems that we’ve heard a lot about tree epidemics and infestations in recent years. But are our trees really more vulnerable to disease than they used to be? And if they are, what is the reason, and what can be done about it?
Perhaps surprisingly, this is an area where the Arts and Humanities have a great deal to contribute, through the work of landscape historians. Using maps, estate records and other documents, an AHRC-funded project -Tree Health and the Structure of Rural Tree Populations in England, c.1550-2015 - has been building up a picture of how British tree populations and tree health have changed over time, and the reasons why.
For Tom Williamson, Professor of Landscape History at the University of East Anglia, one of the interesting questions that this project raises is ‘what is natural’ - how natural is the ‘natural world’? ‘Scientists don’t always appreciate how profoundly unnatural everything is in the British countryside. But you can learn from history - in fact for centuries, our trees have been there because they were planted, or because they were allowed to grow, because their timber and other products were used. It was based on a human decision, in other words: everything was driven by economics.’
Something else that history teaches is that these trees were rarely allowed to reach old age. ‘If you go back 150 years, tree populations were much more intensively managed: most timber trees were cut down before they were 60. Now we have many more middle-aged and ageing trees, and we think that many tree conditions (like oak decline) are related to age. One of the conclusions of our project is that to have a healthy tree population, trees need to be intensively managed.’
But would people stand for the idea of chopping down mature trees? For Tom Williamson ‘the situation we have now is the culmination of an attitude of seeing trees as adornments, rather than as products of an economic system. Tree preservation orders are almost the enemy of trees, but they are based on our false way of thinking about the countryside, as being natural.’
Fortunately there is an alternative to a return to intensive management of trees in the countryside, and this forms the basis of the policy advice that Tom Williamson and his colleagues have been providing, to bodies including the Woodland Trust. ‘Our project has shown that having diversified tree planting would reduce epidemics. In the past there were minority trees making up between five and 10 percent of the total population, and this greater diversity seems to have made the total population more resilient to disease. But these minority trees were regionally specific - so in west Hertfordshire you would have aspen, cherry and apple trees,for example. We suggest that it is a good idea to diversify, by emphasising the minority trees that are characteristic of each area. You use a wider planting palette with reference to the historical situation. In other words - you reintroduce the species that are tried and tested in particular localities.’
Finally, for Tom Williamson ‘this is an excellent example of what the Arts and Humanities can add to our understanding of the environment. Natural scientists often start from the wrong place, beginning with the world as it is, not with how it got there. You don’t see the structured nature of the tree population until you look at it historically. But once you do, you see possible ways of making our trees healthier.’
Natural scientists often start from the wrong place, beginning with the world as it is, not with how it got there. You don’t see the structured nature of the tree population until you look at it historically. But once you do, you see possible ways of making our trees healthier.’
Image credit: Rawdon Fox on Flickr by CC2.0