Ash dieback is an environmental calamity that will cost Britain £15 billion

A research paper published today estimates that the cost of ash dieback in Britain will reach a shocking £15 billion. I was privileged to have supported lead author Louise Hill as an external supervisor, and to be a co-author of this important paper.

Behind the scenes, in the run up to publication, the findings of the paper have caused considerable ‘excitement’, and this is why:

• The total cost of Ash dieback to the UK is estimated to be £15 billion
• Half of this cost (£7 billion) will come be over the next 10 years
• The total cost is 50 times greater 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
• There are 47 other known tree pests and diseases that could arrive in Britain and which may cost an additional £1 billion or more

Ash dieback will cost British society one-third more than the foot-and-mouth outbreak of 2001. In fact, it is likely to be the largest economic impact to British society so far caused by a preventable environmental calamity.

Gabriel Hemery

The mortality expected among Britain’s ash trees is expected to result in 95% of the county’s 150 million ash trees dying over the next few years. This will be a far greater disaster than the loss of elm in the 1970s. Some papers have suggested that mortality in Europe has averaged (75-85%), yet data from 11 recent academic papers from European scientists suggest it will average 94.3% (range 86.1-99%). Note also, that such calculations do not include the impact of human reaction to the disease, in the form of tree felling (for example due to health & safety concerns), and that Britain’s humid climate is expected to cause more severe disease than in much of Europe. Full details on these papers and calculations are provided in the supplementary Excel workbook which accompanies the paper.

Ash dieback is not ‘natural’. It was introduced into Europe from Asia on planting material, and then from Europe to UK when diseased ash trees were imported and then planted across UK, despite warnings from scientists at the time. It probably also spread across the channel via airborne spores, but the original introductions and subsequent rapid spread were as a direct result of tree imports and planting.

It is evident that we cannot stop ash dieback, so our top priority must be preventing other diseases arriving by improving biosecurity at our borders. So, these are my key messages arising from this work:

1. Governments worldwide should take biosecurity more seriously.
2. UK government should revise its mortality estimates for ash dieback, and plan accordingly.
3. Market failure is driving the value of trade in live plants. The value of the market is small compared to the costs arising from poor biosecurity.
4. Tree disease (and pathogen) outbreaks are increasing exponentially in Britain, largely driven by trade. A large number of potential other threats are looming — including oak wilt fungus (Ceratocystis fagacearum), bot canker fungus (Diplodia corticola), and the bacterium Xyella fastidiosa) — all of which could lead to multiple and overlapping epidemics which could devastate our trees.
5. Local authorities will be hit with costs at least 200% greater than their average current tree health budgets. Dead trees cause an immediate and significant risk to human health, particularly near to the transport network. Central government will need to intervene by providing emergency funding.
6. Research funding needs to be increased significantly. UK government research has awarded £6.7 million since the arrival of ash dieback, yet this represents less than 1% of the estimated costs of the disease.

Read the full paper:

Download the full paper:
www.cell.com/current-biology/fulltext/S0960-9822(19)30331-8

Paper DOI:
10.1016/j.cub.2019.03.033

Paper citation:
Hill, L, G Jones, N Atkinson, A Hector, G Hemery, and N Brown. 2019. “The £15 Billion Cost of Ash Dieback in Britain.” Current Biology 29 (9): R315–16. http://dx.doi.org/10.1016/j.cub.2019.03.033

Biology 29 (9): R315–16. http://dx.doi.org/10.1016/j.cub.2019.03.033

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Further reading:

• Plant Biosecurity Strategy for Great Britain, Defra
• My previous posts about ash dieback
• My other scientific papers
• This paper is the third paper arising from Louise Hill’s work:

• Hill, L, G Hemery, A Hector, and N Brown. 2019. “Maintaining Ecosystem Properties after Loss of Ash in Great Britain.” Journal of Applied Ecology 56 (2): 282–93. https://doi.org/10.1111/1365-2664.13255.
• Hill, L, A Hector, G Hemery, S Smart, M Tanadini, and N Brown. 2017. “Abundance Distributions for Tree Species in Great Britain: A Two-Stage Approach to Modeling Abundance Using Species Distribution Modeling and Random Forest.” Ecology and Evolution 7 (4): 1043–56. https://doi.org/10.1002/ece3.2661.