Manage woodland edges for maximum habitat heterogeneity
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Adult butterflies and moths, and their caterpillars, often have different habitat requirements but poor dispersal ability, and therefore creating a varied habitat structure is important for producing habitat suitable for each life stage within a small area (Schultz et al. 2008). Where woodland meets adjacent, open habitat, hard, straight edges provide little habitat diversity for butterflies and moths. Creating a more varied structure to the woodland edge, by felling some trees, encouraging scrub growth, or “scalloping” to increase the length of the edge, may be beneficial to a range of butterfly and moth species.
Schultz C.B., Russell C. & Wynn L. (2008) Restoration, reintroduction, and captive propagation for at-risk butterflies: A review of British and American conservation efforts. Israel Journal of Ecology & Evolution, 54, 41–61.
Supporting evidence from individual studies
A replicated, site comparison study in 2001–2005 in 63 woodland edges and hedgerows in an agricultural landscape in Flanders, Belgium (Merckx & Berwaerts 2010) found that scalloped woodland edges contained more brown hairstreak Thecla betulae eggs than woodland edges with straight borders. There were more brown hairstreak eggs on blackthorn Prunus spinosa bushes in scalloped woodland edges than in straight woodland edges (data presented as model results). Woodland edges and hedgerows (1–250 m long, 2,260 m total) containing blackthorn were divided into 10-m sections (335 woodland sections), and categorized as “scalloped”, “oval”, “boxed” or “with gaps” (exact descriptions not provided). Each winter from 2001–2005, all blackthorn bushes were systematically searched for brown hairstreak eggs.Study and other actions tested
A replicated, paired, controlled, before-and-after study in 2009–2011 in 15 coniferous forest stands in Vihti and Jokioinen, Finland (Korpela et al. 2015) found that felling trees at the woodland edge, in addition to thinning the adjacent woodland, increased the abundance of specialist butterflies and the total species richness of butterflies, moths and bumblebees (Bombus spp.) combined. Two years after felling and thinning, the abundance of specialist butterflies (3.5 individuals/plot), and the total species richness of butterflies, moths and bumblebees (10.7 species/plot), were higher in felled forest edges than in forest edges which had not been felled (butterfly abundance: 0.5 individuals/plot; total richness: 3.6 species/plot). Prior to felling, both butterfly abundance and total species richness were similar in the plots designated for felling (butterfly abundance: 0.5 individuals/plot; total richness: 6.4 species/plot) and no felling plots (butterfly abundance: 0.7 individuals/plot; total richness: 6.2 species/plot). In winter 2009–2010, in each of 15 forest stands, a 50-m-long forest edge was logged. Logging comprised felling a 5-m-wide strip at the forest edge, and behind that a 20-m-wide belt was thinned to a basal area of 8 m2/ha. Trunks were removed, but other debris was left on the ground. A second 50 × 25 m area at each site, within 8–61 m of the logged area, was left unlogged. From late May–August 2009–2011, butterflies, diurnal moths and bumblebees were surveyed seven times/year in each logged and unlogged area, at two-week intervals.Study and other actions tested