Do the effects of crops on skylark (Alauda arvensis) differ between the field and landscape scales?

Christophe Sausse,Frédéric Jiguet,Philippe Martin,Aude Barbottin

doi:10.7717/peerj.1097

Abstract

The promotion of biodiversity in agricultural areas involves actions at the landscape scale, and the management of cropping patterns is considered an important means of achieving this goal. However, most of the available knowledge about the impact of crops on biodiversity has been obtained at the field scale, and is generally grouped together under the umbrella term “crop suitability.” Can field-scale knowledge be used to predict the impact on populations across landscapes? We studied the impact of maize and rapeseed on the abundance of skylark (Alauda arvensis). Field-scale studies in Western Europe have reported diverse impacts on habitat selection and demography. We assessed the consistency between field-scale knowledge and landscape-scale observations, using high-resolution databases describing crops and other habitats for the 4 km2 grid scales analyzed in the French Breeding Bird Survey. We used generalized linear models to estimate the impact of each studied crop at the landscape scale. We stratified the squares according to the local and geographical contexts, to ensure that the conclusions drawn were valid in a wide range of contexts. Our results were not consistent with field knowledge for rapeseed, and were consistent for maize only in grassland contexts. However, the effect sizes were much smaller than those of structural landscape features. These results suggest that upscaling from the field scale to the landscape scale leads to an integration of new agronomic and ecological processes, making the objects studied more complex than simple “crop ∗ species” pairs. We conclude that the carrying capacity of agricultural landscapes cannot be deduced from the suitability of their components.

Highlights

Actions favoring biodiversity in agricultural areas in Europe have been inspired by the principle of “wildlife-friendly farming,” known as “land-sharing” between farmers and heritage and common species (Green et al, 2005)
We studied the effects of rapeseed and maize on skylark densities throughout France, stratifying landscapes according to local and geographic contexts, to ensure that our conclusions were valid for a large range of contexts
Our study highlighted the lack of consistency between the responses of skylark populations at the landscape and field scales

Summary

Introduction

Actions favoring biodiversity in agricultural areas in Europe have been inspired by the principle of “wildlife-friendly farming,” known as “land-sharing” between farmers and heritage and common species (Green et al, 2005). These actions constitute a win–win strategy, in which conservation goals are met and economic profit is achieved, through. Cropping patterns are designed at the landscape scale, which is more appropriate than the field scale for the assessment and preservation of biodiversity (Burel et al, 1998; Tscharntke et al, 2005). They are more labile than fixed landscape elements, as they change every year due to crop rotation and over periods of several years under the influence of market forces and public policies

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