The drivers of avian abundance: patterns in the relative importance of climate and land use

Christine Howard,Richard D Gregory,Stephen G Willis,James W Pearce‐Higgins,Philip A Stephens

doi:10.1111/geb.12377

Abstract

AbstractAimClimate and land use can have important effects on the local abundances of species, but few studies have investigated the relative impacts of these factors. Here, we quantify the relative importance of climate, land use and surrounding population size in determining the abundances of birds across a continent.LocationEurope.MethodsWe used species abundance models to identify the relative importance of different environmental predictors for estimating the local abundances of 342 species of European breeding birds. Models controlling for phylogeny were used to relate species life history and ecological traits to the climate:land use importance ratio. The mean of this ratio, across all species occurring in a given area, was mapped to explore spatial variation in the major drivers of abundance.ResultsAt the scale examined, climate is generally more important than land use in determining species abundances. However, the abundance of species in neighbouring areas is also a major correlate. Among climate variables, temperature is of greater importance than moisture availability in determining abundances. The relative importance of these variables varies with latitude, with temperature being most important in the north, and moisture availability in the south. Differences in the importance of specific drivers are related to species ecological traits: climate is more important for determining the abundance of species that have larger global ranges or a smaller body mass.Main conclusionsAbundances of species occurring in northern Europe, an area predicted to experience climatic changes of high magnitude, are most sensitive to climate, particularly temperature. Given the greater confidence in future projections of temperature than precipitation, this increases confidence in projections of the impacts of climate change on species in the north, whilst attempts to predict future populations in central and southern Europe may be dependent on less predictable changes in land use and precipitation.

Highlights

Climate change has been implicated as a major driver of recent variations in the distributions and abundances of birds (Green et al, 2008; Gregory et al, 2009; Illán et al, 2014)
Ecologists frequently use climate projections to predict, through species distribution modelling (SDM), the risks that species face under particular climate change scenarios (Elith et al, 2010)
We examine whether the relative contribution of climate and land use varies among species in relation to ecological traits

Summary

Introduction

Climate change has been implicated as a major driver of recent variations in the distributions and abundances of birds (Green et al, 2008; Gregory et al, 2009; Illán et al, 2014). The intensification of agricultural practices across Europe during the last quarter of the 20th century led to widespread changes in the abundance and distribution of many farmland bird populations (Donald et al, 2001). To account for such confounding issues, land use variables have been incorporated into SDMs and shown to improve their explanatory power significantly (Thuiller et al, 2004). To understand the susceptibility of species to climate change, we must first disentangle the relative importance of climate and land use in determining abundance at a scale encompassing the large majority, if not the entirety, of a species’ range

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Conclusion