The legacy of 20th century landscape change on today's woodland carabid communities
Abstract
Aim: For many species, the effects of landscape change can involve a time-lag and result in an extinction debt. The landscape matrix plays a vital role in supporting species populations. However, the importance of the historical composition and configuration of landscape mosaics has received little attention, with studies focusing on the effects of loss and fragmentation of single (focal) habitat over time. We investigated the importance of historical and contemporary landscape heterogeneity (composition and configuration) to identify how landscape change has, and is continuing to have, an effect on current woodland carabid communities.
Location: Lowland Britain.
Methods: Carabids were sampled from woodlands in 36 tetrads of 4 km2. Ordination methods analysed current community response to representations of contemporary and historical (1930s) landscape heterogeneity. The effects of 80 years of landscape change on current carabid assemblages were compared among tetrads.
Results: Results are consistent with an extinction debt; carabid communities correlated significantly with the historical composition and configuration of the landscape, but not contemporary landscape configuration. Community assemblages have been shaped, and many species remain affiliated with landscape conditions that no longer exist, notably, large patches of broadleaf woodland and semi-natural grassland. Recent introduction of conifer plantations has had a negative effect on the abundance of many woodland species. For many common, slow-dispersing species, contemporary and historical landscapes offered sub-optimum woodland coverage indicating a lag effect that exceeds 80 years. Increased arable land cover and loss of semi-natural grassland and heathland points towards an ongoing detrimental impact on carabid populations.
Main conclusions: Compared with focal-habitat studies, the landscape mosaic approach provides a more comprehensive understanding of the effects of widespread landscape change on species communities. Conservation guidance includes new planting, maintenance and restoration of semi-natural habitats, implemented across multiple spatial scales and where feasible, considering both historical and contemporary landscape heterogeneity.