Research from Spain and Sweden in Europe, Brazil, Australia, California and many other parts of the world, provides grim evidence of massive declines of some of the largest organisms on earth – old trees (Lindenmayer et all, Science vol 338 7 December 2012). If populations continue to collapse, as predicted, with them will also disappear the ecological, historic and landscape roles of these keystone structures that cannot be provided by younger trees. John Muir, founding figure of the conservation movement in the USA and a passionate advocate for the giant redwoods of Yosemite National Park (population decline of 24% between the 1930s and 1990s) is no doubt turning in his grave.
Why are large old trees disappearing? As individual trees they are exceptionally vulnerable to a wide range of impacts – intentional removal, new pests and diseases, root compaction and damage, fire and competition – to name a few of the major culprits. However the biggest danger is that the loss is iterative and cumulative – one tree here, another there, so it is remarkably difficult to see the overall picture until very late in the day. Humanity is only just waking up to how valuable they are and putting them in the same category as tigers and whales.
The UK is seriously affected too. Devastating outbreaks of new diseases and pests are threatening large old trees in our own backyard. Where once we could boast that our heritage of ancient and veteran trees was perhaps second to none in northern Europe, the situation is changing fast. The latest threat to our large old trees comes from ash dieback but there is a number of emerging tree diseases which have the potential to become epidemics, resulting in further drastic loss of ancient and other special trees.
The Woodland Trust has a three point plan to ensure that the risks are kept to the minimum. While it appears that we cannot stop the rampage of ash dieback we might be able to find resistant trees among the ancient and veteran trees on the Ancient Tree Hunt database. Carry on recording important ash trees and monitor their progress by adding comments to the record blog and uploading an image annually. Through the database we may then be able to identify those trees which are surviving and those that are succumbing. Either way we will be capturing a landscape that we could lose temporarily, enabling us to repopulate it in future with resistant ash or other species of tree.
Jill Butler, Conservation Adviser (Ancient Trees)