Agricultural intensification drives butterfly decline

Abstract

1. Severe losses of insects have taken place over major parts of Europe. This negative trend is assumed to be largely the result of agricultural intensification.2. To analyse potential factors causing this loss of species, we assessed butterfly communities at 21 grassland patches. Seventeen of these were distributed across an agricultural landscape dominated by crop fields; four were embedded in two adjoining managed semi-natural grassland areas. We assessed environmental parameters such as patch size and habitat quality for each grassland patch. We further incorporated the surrounding land-cover considering different degrees of land-use intensity. We classified butterfly species into generalists and specialists according their ecological and behavioural characteristics.3. As in the managed semi-natural reference grasslands, species richness and abundance were higher in patches surrounded by extensively used grasslands and unsprayed crop fields, and lower in patches surrounded by sprayed crop fields. Furthermore, blossom density positively affected butterfly occurrence.4. Our data revealed that specialised butterfly species mainly occur in managed semi-natural grassland sites, and are largely absent from other grassland plots embedded in the agricultural matrix.5. Our study underlines the negative impacts of intense conventional agriculture on butterfly species richness and abundance and reveals the urgent need for more nature-friendly cultivation methods. In situ experiments may help to understand and disentangle single drivers causing this negative trend.

Toward a standardized quantitative and qualitative insect monitoring scheme

“…Nocturnal lepidopterans are very rich in species and comparatively well understood in terms of taxonomy and ecology (Haslberger & Segerer, 2016; Hering, 1951; Kristensen, 1999; Scoble, 1995). Many representatives of this taxon react highly sensitive onto environmental changes such as land use intensification and the deterioration of habitat quality (Bayerisches Landesamt für Umweltschutz, LFU, 2003; Ekroos, Heliölä, & Kuussaari, 2010; Habel, Ulrich, Biburger, Seibold, & Schmitt, 2019; Sánchez‐Bayo & Wyckhuys, 2019). Thus, this second approach, automated light trapping and active sampling at a light tower, provided in total 3,738 individuals and 371 lepidopteran species, including 20 Red List species.…”

Factors contributing to the decline of an endangered flightless longhorn beetle: A 20‐year study

“…Nilsson et al, 2008;Augenstein et al, 2012;Habel et al, 2016). Another frequently used method to examine potential drivers of insect declines is the space-for-time approach, in which the insect diversity in heavily impacted habitats is compared with diversity in less impacted or assumingly undisturbed (control) habitats at the same time (Habel et al, 2019). Still other studies are based on data of long-term monitoring projects (Conrad et al, 2006;Hallmann et al, 2017;Homburg et al, 2019).…”

“…Indeed, atmospheric nitrogen influxes from agriculture, industry and traffic negatively impact habitat quality, especially in nitrogen-limited ecosystems such as semi-natural grasslands (Wallis de Vries & Van Swaay, 2006). Furthermore, pesticides are known to negatively impact insect diversity, either directly due to drifting insecticides (Geiger et al, 2010), or indirectly by the elimination of potentially important larval food plants and/or nectar sources (for pollinating insects) with herbicides (González-Varo et al, 2013;Habel et al, 2019). In our study, 12 sites were distributed across agricultural landscapes dominated by crop fields (Fig.…”

“…Nonetheless, several other studies provided evidence that intensification of cropland is the major driver of the decline of insect abundance and species richness in agricultural landscapes (Ollerton et al, 2014;Thomas, 2016;Ernst et al, 2017). For example, negative impacts of intensive conventional agriculture on butterfly species richness and abundance were recorded in semi-natural grassland in Germany (Habel et al, 2019). Specialised butterfly species were mainly found in semi-natural grassland patches, and were largely absent from other grassland patches embedded in an intensively managed agricultural matrix.…”

“…Intensive agriculture entails the planting of large, uniform monocultures, the removal of trees and hedgerows in order to facilitate mechanisation and the recurrent use of pesticides for controlling crop pests (insecticides), competing weeds (herbicides) and fungal infections (fungicides; Dudley & Alexander, 2017). Intensified land use is shifting multiple insect communities towards species-poor assemblages dominated by a few generalist species, while specialist species are going extinct (White & Kerr, 2007;Habel et al, 2019;Sanchez-Bayo & Wyckhuys, 2019).…”