# Patterns and Drivers of Pest and Disease Occurrence in UK Treescapes

## TL;DR

This study maps tree pest and disease risks across the UK and identifies factors like urbanization and deforestation that drive their spread.

## Contribution

The paper introduces a novel integration of species distribution models and causal inference to analyze pest and disease patterns in UK treescapes.

## Key findings

- Broadleaved trees show pest and disease hotspots in England, while conifers are more affected in Scotland.
- Urban areas, human population density, and recreation drive risks for native broadleaves.
- Conifer risks are linked to woodland connectivity, afforestation, and conifer coverage.

## Abstract

Tree pests and diseases are a key threat to woodland biodiversity and commercial forestry worldwide. In the UK, the ongoing spread of pests and diseases is severely affecting a range of nationally important tree species, resulting in substantial ecological and economic impacts. As the risk posed by pests and diseases varies across the UK's treescapes, understanding the patterns of risk and the factors underlying these patterns is crucial for designing and implementing effective mitigation strategies. To address this challenge, we modelled the distribution of pests and diseases across mainland Great Britain, focusing on the total pest and disease burdens for nine host tree species of particular ecological, economic and cultural importance. Using integrated species distribution models, we combined two datasets—totalling 18,871 pest and disease records across 22 years—to model the spatial patterns of risk. To examine the factors underlying these distributions, we used graph‐based causal inference approaches to inform our model design and to explore the robustness of our conclusions to variations in our modelling assumptions. We found that pest and disease burdens for broadleaved host trees exhibited hotspots in England, while burdens for conifer hosts tended to be high in Scotland. We identified urban area, human population density and local recreation as important drivers for several species, mainly native broadleaves. By contrast, woodland connectivity, afforestation and the level of conifer coverage were the most important drivers of pest and disease burdens for conifer hosts. Deforestation was also an important driver, with effects on pest and disease burdens for both conifers and broadleaves. Our findings have implications for the management of the UK's treescapes in the face of continuing threats from tree pests and diseases, including supporting targeted surveillance and the prioritisation of tree species for future planting.

Tree pests and diseases can be very damaging to natural and commercial forests. We studied how the risk of tree pests and diseases varies across mainland Great Britain and explored how factors such as urbanisation and recreational visits affect the level of risk in different places.