David J. Perović

Landscape simplification filters species traits and drives biotic homogenization

Biodiversity loss can affect the viability of ecosystems by decreasing the ability of communities to respond to environmental change and disturbances. Agricultural intensification is a major driver of biodiversity loss and has multiple components operating at different spatial scales: from in-field management intensity to landscape-scale simplification. Here we show that landscape-level effects dominate functional community composition and can even buffer the effects of in-field management intensification on functional homogenization, and that animal communities in real-world managed landscapes show a unified response (across orders and guilds) to both landscape-scale simplification and in-field intensification. Adults and larvae with specialized feeding habits, species with shorter activity periods and relatively small body sizes are selected against in simplified landscapes with intense in-field management. Our results demonstrate that the diversity of land cover types at the landscape scale is critical for maintaining communities, which are functionally diverse, even in landscapes where in-field management intensity is high.

Multi-country evidence that crop diversification promotes ecological intensification of agriculture

Global food security requires increased crop productivity to meet escalating demand1–3. Current food production systems are heavily dependent on synthetic inputs that threaten the environment and human well-being2,4,5. Biodiversity, for instance, is key to the provision of ecosystem services such as pest control6,7, but is eroded in conventional agricultural systems. Yet the conservation and reinstatement of biodiversity is challenging5,8,9, and it remains unclear whether the promotion of biodiversity can reduce reliance on inputs without penalizing yields on a regional scale. Here we present results from multi-site field studies replicated in Thailand, China and Vietnam over a period of four years, in which we grew nectar-producing plants around rice fields, and monitored levels of pest infestation, insecticide use and yields. Compiling the data from all sites, we report that this inexpensive intervention significantly reduced populations of two key pests, reduced insecticide applications by 70%, increased grain yields by 5% and delivered an economic advantage of 7.5%. Additional field studies showed that predators and parasitoids of the main rice pests, together with detritivores, were more abundant in the presence of nectar-producing plants. We conclude that a simple diversification approach, in this case the growth of nectar-producing plants, can contribute to the ecological intensification of agricultural systems.

Land-use intensification causes multitrophic homogenization of grassland communities.

Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

Geostatistical analysis shows species-specific habitat preferences for parasitoids

Abstract Parasitoids are known to inhabit native vegetation on Australian farms but the extent to which they spill-over into nearby crops is not clear. Geostatistical analysis of parasitoid distribution data showed that vegetational preference and spill-over between native vegetation and cotton fields are highly variable, even between congenerics.

Rubidium labelling demonstrates movement of predators from native vegetation to cotton

Abstract We employed rubidium labelling to track the movement of arthropod natural enemies from a shelterbelt into an adjacent cotton field. Findings demonstrate that Dicranolaius bellulus (Coleoptera: Melyridae) and Oxyopes spp. (Araneae: Oxyopidae) move from the shelterbelt into the crop interior. Capture of rubidium-marked arthropod-predators within the cotton field provides the first hard evidence that semi-natural perennial habitats such as shelterbelts on cotton farms in Australia act as a resource for arthropod predators in adjacent crops.