Agri‐environment conservation set‐asides have co‐benefits for connectivity

• Published in: Ecography (Copenhagen) 2020-10, Vol.43 (10), p.1435-1447
• Main Authors: Threadgill, Katie R. D., McClean, Colin J., Hodgson, Jenny A., Jones, Naomi, Hill, Jane K.
• Format: Article
• Language: English
• Subjects: agri-environment scheme; Agricultural land; Biodiversity; Climate change; Computer simulation; Connectivity; Conservation; Dispersal; Dispersion; Expanders; Grasslands; Insects; Landscape; metapopulation; Metapopulations; persistence; Population density; range expansion; Range extension; Species
• ISSN: 0906-7590; 1600-0587
• DOI: 10.1111/ecog.05127

Widespread declines in farmland biodiversity have led to state‐funded schemes which take land out of production to create (semi‐)natural habitats for biodiversity (e.g. EU agri‐environment schemes; US Conservation Reserve Program). Common features of such schemes are grassland strips at the edges of agricultural fields, and we examine potential co‐benefits of these biodiversity set‐asides for contributing to grassland connectivity. Although set‐aside strips had negligible impact on landscape‐scale species persistence (using metapopulation models parameterized for flying insects run on 267 landscapes of ~30 000 ha across England), they nonetheless improved connectivity in 74% (198/267) of landscapes (comparing landscapes with and without set‐asides), as shown by range expansion rates increasing by up to 100%. Benefits of set‐aside strips varied according to species type (high/low dispersal, high/low population density), but had little benefit for species with low dispersal and small population sizes, which generally failed to expand. High dispersal/high density species were already successful expanders regardless of set‐asides (> 75% of simulations were successful without set‐asides) although expansion rates were still improved when set‐asides were added. Whilst alternative strategies for placement of set‐aside strips (more/less aggregated), revealed no consensus ‘better’ strategy across species types, set‐aside benefits were generally greatest in landscapes with intermediate availability of semi‐natural grassland (0.5‐4% cover). We conclude that small‐scale set‐asides have the potential to improve connectivity, which we expect to help some species track climate change, and connect habitat patches within existing climate space for others. However, set‐asides are unlikely to benefit low dispersal species which are probably at greatest risk from agricultural intensification.