What can studies of woodland fragmentation and creation tell us about ecological networks? A literature review and synthesis

Abstract

The development of ecological networks could help reverse the effects of habitat fragmentation on woodland biodiversity in temperate agricultural landscapes. However, efforts to create networks need to be underpinned by clear evidence of the relative efficacy of local (e.g. improving or expanding existing habitat patches) versus landscape-scale actions (e.g. creating new habitat or corridors in the landscape matrix). Using cluster analyses we synthesised the findings of 104 studies, published between 1990 and 2013 focusing on the responses of woodland vascular plant, vertebrate, cryptogam and invertebrate species to local and landscape variables. Species responses (richness, diversity, occurrence) were strongly influenced by patch area, patch characteristics (e.g. stand structure) and isolation (e.g. distance between habitat patches). Patch characteristics were of overriding importance for all species groups, especially cryptogams. Many studies recording significant species responses to patch characteristics did not record significant responses to patch area and vice versa, suggesting that patch area may sometimes act as a surrogate for patch characteristics (i.e. larger patches being of ‘better quality’). Ecological continuity was important for vascular plants, but assessed in only a few vertebrate and invertebrate studies. Matrix structure (e.g. presence of corridors) was important for vertebrates, but rarely assessed for other species groups. Actions to develop ecological networks should focus on enhancing the quality and/or size of existing habitat patches and reducing isolation between patches. However, given that very few studies have assessed all local and landscape variables together, further information on the relative impacts of different attributes of ecological networks in temperate agricultural landscapes is urgently needed.