Horizon scanning for tree health

Project lead(s)   Katy Dainton | Forest Research
Organisation lead  Forest Research
Contributors/partners   Hannah Gruffudd, Daegan Inward, Mike Bell, Gary Kerr, Bill Mason (Forest Research), Kathy Bleiker (Canadian Forest Service), US Department of Agriculture (USDA)

Project status   Active (Duration 4 years)

Project funding  £247,025
Research outcome   Resistance I Response I Adaptation
Choristoneura occidentalis
British forestry is highly reliant upon non-native tree species, with two-thirds of conifer plantations consisting of species which originate from coastal western North America, most notably Sitka spruce and Douglas Fir. These are critical species for storing carbon, new woodland creation, and commercial softwood production. Identifying potential future threats to these trees is critical to ensure future forest health and to inform new tree planting schemes. Most plantations have remained largely free of pests and diseases until recently, but the newly introduced bark beetle Ips typographus and a disease caused by the pathogen Phytopthora pluvialis are currently a problem. The threat of pests and diseases is made worse by both climate change and by creating plantations of trees of the same age and a single species.

Today there is a worldwide pool of potentially damaging organisms that could enter the UK, so robust “horizon scanning” methods are needed to predict future risks. A completed Centre for Forest Protection pilot project highlighted that existing methods are limited in their ability to reliably identify future threats to a particular tree species. Limitations include failure to use local-scale future climate projection data, which provides data on changes in growing conditions, and risks such as increased drought and climatic suitability for the pest/pathogen. There is also an overreliance on professional judgement and traditional pest risk assessment by experts.

Research aims and objectives
The overall goal of this project is to develop a comprehensive and multi-factor horizon scanning approach to identify, risk assess, and mitigate potential forest health threats to principal tree species planted in the UK.

Our research objectives are to:

  • Develop a clearly defined methodology to identify potential forest health threats to important British-grown tree species, particularly the potential impacts of predicted environmental change.
  • Investigate how key tree species respond to, and recover from, changes in their native and planted ranges, and how trees of different origins vary in their response to different stressors.
  • Investigate how management approaches are evolving to adapt to forest health and climate change impacts in the origin countries of the trees and use this information to inform future UK management approaches.
Project description

Threats: pests and pathogens that have the potential to damage British grown trees will be identified using evidence from their native range. The damage scoring system developed in the pilot study will be refined and applied to lists of native and introduced pests and pathogens of specific trees in their native ranges.

Drivers: key drivers of damage (e.g. tree condition, environmental factors) will be identified using local observation reports, wider literature, and expert knowledge from project partners. Threats will be clustered based on similar responses to drivers (e.g. increased damage following drought).

Mitigation/adaptation methods: forest management methods and policies will be investigated to identify those used to tackle forest health and climate change impacts, for example, through tree improvement efforts (e.g. breeding for improved resistance to pests) and changing planting policies.

Risk model: a suitable method will be selected to build a risk model to assess clustered threats in their native range. Analysis and modelling will be conducted using methods identified by the pilot project to analyse the bioclimatic factors contributing to poor health of key tree species in their native ranges. The model will then be applied to British grown trees to create a risk map for key threats identified earlier in this project.

Aerial view of defoliation by the western spruce budworm in Mount Hood National Forest.

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