Roadside habitat impacts insect traffic mortality

Published source details Keilsohn W., Narango D.L. & Tallamy D.W. (2018) Roadside habitat impacts insect traffic mortality. Journal of Insect Conservation, 22, 183-188.
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This study is summarised as evidence for the following.

	Action	Category
	Restore or maintain species-rich grassland along road/railway verges Action Link

Restore or maintain species-rich grassland along road/railway verges

A replicated, site comparison study in 2015 on 30 roads in Delaware, Maryland and Pennsylvania, USA (Keilsohn et al. 2018) found that more butterflies and other insects including moths were killed on roads with meadow verges than on roads bordered by mown, non-native grasses or woods, and mortality was higher on roads with habitat in the central reservation. The number of dead butterflies on roads with meadow verges (2.9–10.0 individuals/site) was higher than on roads with mown grass verges (1.0–3.9 individuals/site) or wooded verges (0.3–0.8 individuals/site). In addition, the number of dead butterflies was higher on roads with habitat in the central reservation (0.8–10.0 individuals/site) than on roads with no habitat in the central reservation (0.3–2.9 individuals/site). The results for other insects, including moths, were similar (see paper for details). Thirty road sections, 200 m long, >400 m apart, with speed limits between 70–105 km/h and high traffic volumes, were classified to three habitat categories: meadow verges dominated by wildflowers and tall grass; frequently mown, short, non-native grass verges; and wooded verges dominated by trees and shrubs. Roads were further split by the presence or absence of a vegetated central reservation. In June 2015, all dead insects were initially removed from the road edge on both sides of the road. From June–July 2015, all dead insects were collected from the road edge five times, at weekly intervals, and identified to species.

(Summarised by: Andrew Bladon)