Are woodland creation schemes providing suitable resources for biodiversity? Woodland moths as a case study

Abstract

Woodland, like many habitats throughout the world, has been severely affected by habitat loss and fragmentation. Woodland restoration programmes aimed at reversing habitat loss have been in place in many countries over the last 100 years. In particular, agri-environment schemes (AES) to increase the amount and quality of woodland on agricultural land have operated in Europe and Australia for decades (nearly 30 years in the United Kingdom). However, to date there has been very little assessment of their value to biodiversity. We assessed the potential benefits to biodiversity of woodlands planted during 1988–1991 under a woodland grant scheme (WGS in Scotland), according to local and landscape-level habitat characteristics. Specifically, we (1) performed a linear discriminant analysis to compare the characteristics of 24 WGS sites to those of more mature semi-natural woodlands (34 sites >60 years old), and (2) used existing information on the influence of woodland characteristics on a biologically diverse group (i.e. moths) to quantify the benefits of WGS sites to biodiversity. The creation of new WGS patches increased woodland extent and connectivity in the landscape; however, planting that took place adjacent to previously existing woodland did not usually increase connectivity. WGS sites were mainly composed by broadleaved native tree species, but non-native species were also present. In general, WGS sites had lower tree species richness, proportion of native trees, tree basal area and amount of understory, and higher tree densities and canopy cover than more mature semi-natural woodlands. Overall, WGS sites were predicted to have lower moth abundance and species richness than older semi-natural woodlands. However, the magnitude of these differences depended on the habitat specificity and dispersal abilities of different moth groups, suggesting that WGS sites are better at providing suitable resources for generalist species and for species less limited by dispersal. Our findings have important implications for the way in which current woodland creation and management schemes operate in many countries and suggest that: (1) the creation of new woodlands should focus on planting native species, (2) woodland creation schemes are likely to be more beneficial for biodiversity if certain management practices (e.g. thinning to enhance structural diversity and accelerate the transition to later successional stages) accompany the provision of these grants, and (3) spatially-targeted woodland creation would further increase the contribution of AES woodlands to enhance biodiversity.