On the relationship between farmland biodiversity and land-use intensity in Europe

TLDR

Agriculture is a major driver of biodiversity loss, yet the form of the relationship between biodiversity and land‑use intensity remains unclear. The study examined plant species richness against nitrogen input across 271 European grassland and arable sites. Plant species richness declines exponentially with increasing nitrogen input, driven mainly by rare species, implying that conservation gains are disproportionately higher on low‑intensity farmland and that reducing N inputs yields similar species gains in arable and grassland systems.

Abstract

Worldwide agriculture is one of the main drivers of biodiversity decline. Effective conservation strategies depend on the type of relationship between biodiversity and land-use intensity, but to date the shape of this relationship is unknown. We linked plant species richness with nitrogen (N) input as an indicator of land-use intensity on 130 grasslands and 141 arable fields in six European countries. Using Poisson regression, we found that plant species richness was significantly negatively related to N input on both field types after the effects of confounding environmental factors had been accounted for. Subsequent analyses showed that exponentially declining relationships provided a better fit than linear or unimodal relationships and that this was largely the result of the response of rare species (relative cover less than 1%). Our results indicate that conservation benefits are disproportionally more costly on high-intensity than on low-intensity farmland. For example, reducing N inputs from 75 to 0 and 400 to 60 kg ha −1 yr −1 resulted in about the same estimated species gain for arable plants. Conservation initiatives are most (cost-)effective if they are preferentially implemented in extensively farmed areas that still support high levels of biodiversity.