Tree pests and diseases: the threat to biodiversity and the delivery of ecosystem services

The increasing number of invasive pests and pathogens entering North America and Europe indicate that the threat which they pose to forests is increasing concurrently with climate change and globalisation. To date research has mainly focussed on the protection of trees of economic importance. In most countries the major portion of research costs tend to be borne by the state with governments funding tree health research and the implementation of statutory work (risk assessment, border inspection and surveillance), whilst commercial enterprises cover the costs of ongoing management of established pests and pathogens. The costs of responding to new outbreaks tend to be shared with government or regional authorities organising initial response but owners covering subsequent operational costs without state compensation. However in recent years a number of major epidemics have devastated natural ecosystems and landscapes valued both for timber and for their wider benefits to the general public. Against this background it is helpful to consider more explicitly the consequences of pests and pathogens for the full range of ecosystem services. Biodiversity was originally perceived to be an ecosystem service but is now recognised as fundamental in supporting ecological function. Many ecosystem services are uncosted and enjoyed by a range of stakeholders raising important questions about who is responsible for measures to protect tree health. We present data here on the new outbreaks which have occurred in the UK and, as an example of rapid spread of a disease, on the development of Hymenoscyphus fraxineus in the UK over the last 3 years. These data indicate that tree pests and diseases represent a major contemporary problem to which the ecosystem services concept, and its associated implications for cost sharing, can move forward our approach to prevention and outbreak management and may improve the outcomes of international measures to minimise the man-mediated movement and impacts of pests and pathogens.