Biodiversity conservation in agriculture requires a multi-scale approach

Abstract

Biodiversity loss--one of the most prominent forms of modern environmental change--has been heavily driven by terrestrial habitat loss and, in particular, the spread and intensification of agriculture. Expanding agricultural land-use has led to the search for strong conservation strategies, with some suggesting that biodiversity conservation in agriculture is best maximized by reducing local management intensity, such as fertilizer and pesticide application. Others highlight the importance of landscape-level approaches that incorporate natural or semi-natural areas in landscapes surrounding farms. Here, we show that both of these practices are valuable to the conservation of biodiversity, and that either local or landscape factors can be most crucial to conservation planning depending on which types of organisms one wishes to save. We performed a quantitative review of 266 observations taken from 31 studies that compared the impacts of localized (within farm) management strategies and landscape complexity (around farms) on the richness and abundance of plant, invertebrate and vertebrate species in agro-ecosystems. While both factors significantly impacted species richness, the richness of sessile plants increased with less-intensive local management, but did not significantly respond to landscape complexity. By contrast, the richness of mobile vertebrates increased with landscape complexity, but did not significantly increase with less-intensive local management. Invertebrate richness and abundance responded to both factors. Our analyses point to clear differences in how various groups of organisms respond to differing scales of management, and suggest that preservation of multiple taxonomic groups will require multiple scales of conservation.

Keywords: agri-environmental schemes; agroecology; intensification; landscape complexity; organic farming; sustainable agriculture.

Figure 1.

Scatterplots of estimated marginal means and 95% CI (black points) of local management (LR_M) and landscape complexity (Z_L) effect sizes for richness (n = 70 observations, 31 studies) (a) and abundance (b) (n = 62 observations, 28 studies). Outliers were removed from local management analysis, but remained in the landscape complexity analysis (triangular points). Summary statistics of the GLMM used to estimate marginal means and 95% CIs are available in table 1 for richness and table 2 for abundance. (Online version in colour.)

Figure 2.

Estimated marginal means and 95% CI of plant, invertebrate and vertebrate (from left to right) effect sizes for local management (LR_M) for richness (a) and abundance (b), and landscape complexity (Z_L) effect sizes for richness (c) and abundance (d). Summary statistics of the GLMM used to estimate marginal means and 95% CIs are available in table 1 for richness and table 2 for abundance. (Online version in colour.)