The management of lowland neutral grasslands in Britain: effects of agricultural practices on birds and their food resources

Abstract

Summary1. The effects of agricultural intensification on biodiversity in arable systems of western Europe have received a great deal of attention. However, the recent transformation of grassland systems has been just as profound. 2. In Britain, the management of grassland has changed substantially in the second half of the 20th century. A high proportion of lowland grassland is managed intensively. The major changes include a doubling in the use of inorganic nitrogen, a switch from hay to silage, and increased stocking densities, particularly of sheep. Structurally diverse and species-rich swards have been largely replaced by relatively dense, fast-growing and structurally uniform swards, dominated by competitive species. 3. Most of these changes have reduced the suitability of grassland as feeding and breeding habitat for birds. 4. The most important direct effects have been deterioration of the sward as nesting and wintering habitat, and loss of seed resources as food. Short uniform swards afford poor shelter and camouflage from predators, whereas increased mowing intensities and trampling by stock will destroy nests and young. Increased frequency of sward defoliation reduces flowering and seed set, and hence food availability for seed-eating birds. 5. The indirect effects of intensification of management on birds relate largely to changes in the abundance and availability of invertebrate prey. The effects of management vary with its type, timing and intensity, and with invertebrate ecology and phenology, but, in general, the abundance and diversity of invertebrates declines with reductions in sward diversity and structural complexity. 6. Low input livestock systems are likely to be central to any future management strategies designed to maintain and restore the ecological diversity of semi-natural lowland grasslands. Low additions of organic fertilizer benefit some invertebrate prey species, and moderate levels of grazing encourage sward heterogeneity. 7. There is now a need to improve understanding of how grassland management affects bird population dynamics. Particularly important areas of research include: (i) the interaction between changes in food abundance, due to changes in fertilizer inputs, and food accessibility, due to changes in sward structure; (ii) the interaction between predation rates and management-related changes in habitat; and (iii) the impact of alternative anti-helminithic treatments for livestock on invertebrates and birds.

How do sheep affect plant communities and arthropod populations in temperate grasslands?

“…Adding mineral fertilizer inputs has been assumed to decrease the abundance and species richness of epigeal insects, and might not be ecologically sustainable from a grassland fauna conservation standpoint (Fenner and Palmer, 1998;Vickery et al, 2001). However, we were unable to draw any firm conclusions on the benefits of fertilizer cessation or late grazing on arthropod diversity in temperate sheep-grazed pastures, especially given that much of the overview was founded on a very small number of published studies.…”

Interactions between ecosystem properties and land use clarify spatial strategies to optimize trade-offs between agriculture and species conservation

“…This indicates that the most endangered breeding birds were meadow birds (Vickery et al 2001;Atkinson et al 2005) found on less fertilized pastures, whereas sales increased with fertilization. Lower fertilization accompanied less drainage and lower stocking rates, facilitating successful reproduction of meadow birds (Newton 2004;Kentie et al 2013).…”

“…We were not able to collect data on prey abundance and prey energy content. Therefore, we used SOC and CEC as proxies for soil fertility, which we expected to have a positive effect on the plant and animal biomass in soils, as it may form an important base of the food chain exploited by birds (Vickery et al 2001;Wissuwa et al 2013). Fertilization, however, which is commonly associated with the early onset of grazing, an increased number of mowing events, a more uniform sward, and with a lower biomass of grassland invertebrates, should therefore decrease the conservation values of endangered birds and plants (Vickery et al 2001;Newton 2004).…”

Relationship between anthropogenic sewage discharge, marsh structure and bird assemblages in an SW Atlantic saltmarsh

“…Increased arthropods in grass dominated habitats had been associated with increased 329 complexity of plant architecture (Gibson et al, 1992;Dennis et al, 2001), and the 330 increase of vegetation height (Morris and Plant, 1983;Dennis et al, 1997) and 331 heterogeneity (Dennis et al 1998;Vickery et al, 2001). Specifically, the number of 332 herbivore insects increased when the nutritional quality of salt marsh plants improved as 333 a result of higher nutrient loading increased (Vince et al 1981).…”