Developing a national indicator of functional connectivity

Lisbeth A Hordley,Gary D Powney,Tom Brereton,Simon Gillings,Owen L Petchey,David B Roy,Joseph A Tobias,James Williams,Tom H Oliver

doi:10.1016/j.ecolind.2022.108610

Abstract

Habitat loss is a significant driver of biodiversity loss, causing fragmentation into small, isolated patches of suitable land cover. This reduces the permeability of landscapes to the movement of individuals and reduces the likelihood of metapopulation persistence. Quantifying functional connectivity, the ability of a focal species to move between resource patches, is therefore essential for conservation management. There is substantial evidence supporting a technique based on ‘population synchrony’- the degree of correlation in time-series of annual population growth rates between different long-term monitoring sites, to provide a measure of functional connectivity. However, synchronised population dynamics are not only driven by the movement of individuals between sites, but also shared environmental conditions which must be accounted for. Here, we use species survey data from over four decades to investigate average levels and temporal trends in population synchrony for 58 British bird and butterfly species. We first show that population synchrony is significantly associated with synchrony in some seasonal climatic variables. Once we accounted for spatiotemporal climatic patterns, we found that synchrony in butterflies declined over time by 71% between 1985 and 2000 but increased by 64% in recent years. Synchrony in birds showed some decline between 1999 and 2005, after which there appears to being recovery, however most species (74%) show no significant overall change in synchrony. Our proposed indicator provides a ‘species-eye-view’ of functional connectivity using widely available abundance data. Developing such indicators of functional connectivity, which can be updated annually, is crucial to improve the effectiveness of land management strategies for conservation under increasing environmental change.

Highlights

Habitat loss and fragmentation is a key concern of conservation policy both in the UK and globally, as it is implicated as the main driver of biodiversity loss in numerous taxa across a variety of regions (Butchart et al, 2010; Fahrig, 2003; Pimm et al, 2014)
Once these var iables were accounted for, we demonstrated temporal trends in residual population synchrony for UK birds and butterflies, suggesting that functional connectivity is changing over time
Our proposed indicator based on population synchrony offers a datadriven approach to measuring functional connectivity using widely available abundance data which can be updated annually

Summary

Introduction

Habitat loss and fragmentation is a key concern of conservation policy both in the UK and globally, as it is implicated as the main driver of biodiversity loss in numerous taxa across a variety of regions (Butchart et al, 2010; Fahrig, 2003; Pimm et al, 2014). Driven by anthropogenic land-use change, decreases the amount of available habitat and increases ecological isolation between patches. This can result in an increased extinction risk and a reduction in the exchange of individuals among fragmented populations (Hanski, 1998). Functional connectivity, i.e. the ability of individuals and populations to move between resource patches in response to landscape elements, is crucial for managing and conserving viable metapopulations (Hanski, 1998; Tischendorf and Fahrig, 2000). Dispersal across landscapes is essential for range expansion under climate change and the maintenance of genetic diversity (Hanski, 1998; Hanski and Gilpin, 1991)

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Discussion

Conclusion