Context

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 (Picea sitchensis) and Douglas fir (Pseudotsuga menziesii). 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 larger eight-toothed European spruce 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” (HS) 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

Aim:

• Develop a framework for horizon scanning that is innovative, data-driven, and future-focused, which can be applied to other species, including native British species growing in other parts of the world.

Objectives:

• Evaluate existing published horizon scanning approaches for their advantages and limitations.
• Evaluate other risk analysis or biosecurity modelling studies, that can be incorporated into a more targeted analysis for key tree species.
• Identify the data and tools that are available to support HS methods for identifying threats, including pests and diseases, to British grown trees.
• Investigate and determine the value of a collaborative international approach.

Main findings

The rapid review of existing horizon scanning and modelling approaches has identified a range of potential methods and assessed them for gaps and opportunities. We have proposed a framework for a robust, data-driven horizon scanning approach that takes greater account of changing climate and rich, detailed data sources, and recommended a practical workflow for an assessment for Sitka spruce and Douglas-fir.

The project identified opportunities for transdisciplinary research and international collaborative working to tackle forest health issues that cross borders.