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Providing evidence to improve practice

Individual study: Intensive grazing by horses detrimentally affects orthopteran assemblages in floodplain grassland along the Mardyke River Valley, Essex, England

Published source details

Gardiner T. & Haines K. (2008) Intensive grazing by horses detrimentally affects orthopteran assemblages in floodplain grassland along the Mardyke River Valley, Essex, England. Conservation Evidence, 5, 38-44

Summary

Grasshoppers and crickets (Orthoptera) were monitored in the Mardyke River Valley in south Essex in July and August 2007. A standardised transect method was used to count Orthoptera in horse-grazed and ungrazed pastures. Sward height measurements were taken from each pasture. In ungrazed pastures Orthoptera were much more abundant (17.3 individuals/100 m) with greater diversity (7 species) than in grazed pastures (0.8 individuals/100 m; 4 species). The low sward height of the grazed pastures (< 6 cm on average) is considered to have afforded Orthoptera little shelter from inclement weather or avian predators. Based on additional observations, a reduction in the grazing pressure from 3.5 horses/ha (current grazing density to the south of the Mardyke) to less than 2 horses/ha would lead to a more heterogeneous and overall taller sward, which would be favourable for orthopterans and a wider range of other grassland invertebrates.