The effects of landscape context and climate on woodland use by bats: implications for habitat creation

Abstract

There has been growing recognition that simply protecting pristine habitat is insufficient to protect biodiversity in the face of the twin crises of habitat loss and climate change. This, combined with a desire to use functioning ecosystems as carbon sequestration tools, has led to ambitious targets for habitat restoration. Restoration projects are often costly and resource intensive, so strategic planning is required to maximise their benefits. However, evidence is often lacking to inform practitioners of the best strategies. Landscape context can affect the success of restoration projects as edge effects can impact patch quality and the composition and configuration of nearby habitats can promote or impede colonisation. In the UK where habitat loss has been dominated by deforestation, government targets for habitat restoration tend to focus on woodland creation. Bats in the UK use woodland for roosting and foraging and stand to benefit greatly from increased woodland cover resulting from these targets. Here, the impacts of landscape context and climate on bats’ use of woodlands are investigated. Long term population data were used to understand the impacts of heath restoration in conifer forests on bats. In plantations where conifer comprised the majority woodland cover, conversion of conifer to open habitats had negative effects on woodland bats, causing populations to decline or grow at a slower rate. How bat activity responds to woodland and trees outside woodland cover and spatial configuration was assessed by surveying 60 landscapes in two regions of the UK, with limited impacts found across a number of species. In particular, bat activity in woody habitat patches was consistent along a gradient of woodland cover. However, trees outside woodlands (ToW) were found to be incredibly important aspects of agricultural landscapes. Bat activity at such sites were on par with woodland edge, a key foraging habitat, and landscape ToW cover increased occurrence for N. noctula. Activity at ToW sites (and to a lesser extent woodland edge) also increased as the woodland cover was divided into more patches for P. pipistrellus and Myotis spp. while declining in woodland interior sites, suggesting that ToW increased landscape connectivity and matrix permeability as ‘fragmentation per-se’ increased. Multi and cross scale landscape drivers of habitat suitability were investigated at a national scale using nested habitat suitability models. Habitat associations for the 9 most common species of bat in the UK were complex and varied between species and scales considered, however some general patterns emerged. Broadleaf woodland and ToW cover had a positive impact on all species, however there was no strong indication that any particular range of cover increase was most beneficial across all species and scales. Agricultural habitat had mixed effects but high levels of cover tended to be negative. Urban cover also typically negatively affected suitability, although rural buildings allowed for roosts. Additionally, by using a multi-level approach important cross-scale interactions were identified. Spatial patterns and potential land use and climate drivers of emerging Rhinolophus hipposideros population trends were also investigated. National R. hipposideros population recoveries in the UK have slowed in the last decade and this is seemingly driven by declines in the Southwest of England. Yearly growth rates were negatively impacted by winter precipitation anomalies and increasing spring temperatures, while short term (5 year) trends were negatively impacted by increased summer precipitation and urban cover. These impacts did not appear to be concentrated in the Southwest, suggesting that they may not be the main drivers of spatial patterns. Overall, this thesis has highlighted that landscape context can influence woodland benefits to bats, although the effects of urban, agricultural and woodland cover in the landscape are all species and scale specific, complicating recommendations for spatial targeting. However, it seems that planting woodland in varied landscape contexts will benefit at least part of the UK bat community, although concentrating new planting in a smaller number of patches is likely to have the most benefits for woodland specialists. Trees outside woodland also had an important role to play as habitat for bats in agricultural landscapes, particularly in boosting connectivity between fragmented patches and thus sympathetic management and new planting of these should also be promoted.