Did you pack your own trunk? The case for 'plant passports' for UK timber imports in the light of the emergence of ash dieback.
By Laura Plant
The 2010 outcry sprouting from the government's plans to sell off the UK’s forests proved that forests mean a lot more to society than can just be measured in terms of the wood they contain. Our deeply rooted love of trees is exemplified by the common phrase 'touch wood', this is considered to come from the pre-Christian belief that tapping a tree would let the sacred wood spirits know you were there and bestow luck on you.
But why do we care about leaving one species to die when we know other species will expand to fill the empty canopy gaps left by the dying tree? The potential extinction of the common ash tree in the UK due to ash dieback has far wider implications than just the economic loss of the timber value, for example the biodiversity of other plants and animals that it supports and its historical value. Oliver Rackham, famous countryside historian and fellow of Corpus Christi college (Cambridge), has suggested that coppiced ash stools may be some of the oldest living organisms in the country (perhaps even thousands of years old).
Promising research in Denmark, which has lost 90% of its ash trees to ash dieback (Chalara fraxinea), has twigged that there are some resistant trees that show few symptoms and survive in the presence of the fungus. It is predicted that the presence of natural genetic variation in susceptibility will open avenues for natural selection or artificial selection of trees with higher fitness (McKinney et al, 2011).
NWT Lower Wood in Ashwellthorpe, where ash trees are being investigated for suspected Chalara infection. Photo by Lucy Denman, used with permission.Original Article Here
Another issue aside from whether we have seen the end of our beloved ash, stems from this tragedy and that is the danger of emerging infectious diseases (EIDs). EIDs are caused by pathogens that have changed geographical distribution meaning they are now exposed to non-adapted plants that are highly susceptible to infection, or they have undergone some evolutionary change that has led to increased virulence. The underlying factors of these changes in the pathogen can often be traced to human activities for example intensive land use, reduction of biodiversity, increasing globalization of trade and general climate change all of which are predicted to increase in the future. Land use intensity is of particular importance as the forestry sector shifts to the planting of a single species or species clone in monoculture plantations. These trees are vulnerable to EIDs due to their lack of genetic variability but also the fact that plantation tree species tend to allocate fewer resources to their defence systems in the trade-off for faster growth.
So what management implications stem from the threat of EIDs? The consensus over ash dieback is that the spread of the disease needs to be slowed to give time for the cultivation of genetically resistant trees and the restructuring of woodlands. In regards to future prevention of EIDs spreading between continents, there is a case for faster communication of the disease outbreak and then subsequent designation of certified disease-free areas. Trade restrictions from these zones could be monitored by the use of 'plant passports' so the origin of wood can easily be traced. Similar schemes already exist in the sustainable forestry sector, for example the log tracking system in French Guyana consists of a tag that can be broken in two and one half placed on the tree stump and the other half on the cut timber. Hardly a complex scheme, but one that has caused a lucrative branching out of the country's industry into environmentally-conscientious markets that are concerned about timber provenance.
For more information on ash dieback visit www.forestry.gov.uk/chalara