Ash dieback is just the start of diseases threatening Britain’s trees

Published by: at 16th December 2019

Filed under: Uncategorised

As Dutch elm disease spread across Britain in the 1970s, trees were felled, and their loss was a constant topic of conversation. Today, just a few years into the equally devastating ash dieback epidemic, and as the first great trees are toppled, most of us appear to have forgotten all about it. The disease almost everywhere. A survey published this spring found infected trees across roughly three-quarters of England and Wales: the spread has been as rapid and devastating as ecologists predicted. But in this age of hypernormalisation, only a few people still seem to care.

And almost nothing has been learned. Our disease prevention rules do little to prevent similar plagues afflicting our remaining trees. Several deadly pathogens are marching across Europe. While it is hard to prevent some of these plagues from spreading across land, there is a simple measure that would stop most of them from spreading across water: a ban on the import of all live plants except those grown from tissue cultures, in sterile conditions.

The Cost of Ash Dieback

Research led by the University of Oxford estimates the cost of ash dieback (ADB) in the UK at £15bn. Half of this (£7bn) will be over the next 10 years. Those costs comprise clean-up costs at £4bn plus replanting and research, and the loss of profit by the forestry sector.

Calls for biosecurity have, however, often lost out to economic arguments in favour of trade. The total cost is 50 times larger than the annual value of trade in live plants to and from Britain, which is the most important route by which invasive plant diseases enter the country.

The scientists say that the total cost could be reduced by replanting lost ash trees with other native trees, but curing or halting the disease is not possible. They advise that the government’s focus now has to be on preventing introductions of other non-native diseases to protect our remaining tree species.

To see how this has also affected our economy speaks volumes for how important tree health is, and that it needs to be taken very seriously, it is an indication of how devastating climate change can be.

The scientists estimate that another 47 major tree pests and diseases now threaten to arrive in Britain, and these are just the known plagues. In ecological terms, this legislative failure is a total disaster. We face the prospect of tree species everywhere eventually meeting their deadly pathogens. Where logging and climate breakdown have so far failed to eliminate the world’s forests, imported diseases threaten to complete the job.


  • A nationwide replanting scheme could reduce the overall cost by £2.5 billion, by ensuring that lost ecosystem services are replaced
  • Greater focus on and investment in biosecurity and sourcing of safe plant material is needed to keep new diseases out
  • Introduce far tighter controls on imports of all live plants for planting, as this is the largest pathway through which tree diseases are introduced

Every Landscape professional has a responsibility when specifying plant material for a project. The Landscape Institute’s Biosecurity Tool Kit provides guidance for landscape practitioners at every stage of a project, from assessment and planning to design, contract administration and landscape management.