The environmental impacts of biomass crops: use by birds of miscanthus in summer and winter in southwestern England

Abstract

We compared birds in a group of established and well-managed miscanthus (Miscanthus x giganteus) fields in Somerset and East Devon, southwestern England, with plots of short rotation coppice (SRC) willow, arable crops and grassland in two winters and one summer. Following early spring cutting, 19 miscanthus fields grew taller, initially produced greater cover and were less weedy than SRC. As stubble in May, the miscanthus contained broadly similar species at similar densities to arable and grassland comparison plots. By July, at 2-m-tall, miscanthus held higher densities of birds but of fewer species, most of them characteristic of woodland and scrub. SRC, previously identified as being a beneficial crop for many birds, always contained more species and individuals than miscanthus. Throughout each of two winters, 15 miscanthus plots remained unharvested and contained more wood ⁄ scrub species such as Blackbirds Turdus merula, tits, Reed Buntings Emberiza schoeniclus and Woodcock Scolopax rusticola than the comparison plots, which held more corvids and Skylarks Alauda arvensis amongst others. Similar overall mean densities of birds in the miscanthus and the comparison plots masked relatively low density variance in miscanthus and very high variance in the comparison plots. Unharvested miscanthus crops grown in place of habitat types supporting flocks of wintering birds would displace these flocks. Miscanthus plantations with open patches attracted more finches and waders in winter. The two previous studies of birds in miscanthus in the UK found more species and more individuals than we did in summer and winter. Both these studies documented high levels of weediness and patchy crop growth. In the context of this previous work our data suggest that bird use of miscanthus in summer and winter is likely to be variable, affected by region, weediness, crop structure and patchiness. While large-scale cropping of SRC in England is likely to have a positive overall impact on a suite of common farmland and woodland birds, our data suggest that miscanthus in the southwest of England may have an approximately neutral effect.However, some open farmland specialist species may be lost when planting either crop.

Characterising the impacts of emerging energy development on wildlife, with an eye towards mitigation

“…; Sage et al . ). With short‐rotation woody crops, the specific vegetative characteristics of cultivated species influenced nesting propensity for certain species of birds, and therefore, site and species‐specific guidelines will need to be developed in new areas (Verschuyl et al .…”

“…field margins or undisturbed grasslands; Semere & Slater ; Sage et al . ; Riffell et al . ; Robertson et al .…”

Modelling farmer decision-making to anticipate tradeoffs between provisioning ecosystem services and biodiversity

“…This was verified by the more severe decrease in fledgling numbers when the production of bioenergy increases, meaning that the breeding period is shortened and less breeding attempts will occur. However, previous field studies related to bird and bioenergy crops showed that miscanthus supports a higher density of breeding skylarks than other arable crops, but at an early stage of crop establishment when the vegetation does not exceed a maximum threshold (Bellamy et al, 2009;Sage et al, 2010;Semere and Slater, 2007). The high skylark density found in the literature was explained by a significant proportion of bare ground and the presence of weeds on which adults feed.…”

Benefits versus risks of growing biofuel crops: the case of Miscanthus

“…In intensive agricultural landscapes Miscanthus fields may improve biodiversity due to the lack of tilling, reduced pesticide level and the provision of hiding places, especially during winter [13,54]. On the contrary, very few animals feed directly on Miscanthus and if the management of full grown Miscanthus fields becomes so successful that weeds are totally suppressed, and if fields become so large that field margins will constitute only a smaller fraction, the benefits will decrease [54,55].…”