Editor's Choice - Monitoring and evaluating the ecological impact of agri-environment schemes
August 2012 (Issue 49:4)
Baker, D. J., Freeman, S. N., Grice, P. V. and Siriwardena, G. M. (2012), Landscape-scale responses of birds to agri-environment management: a test of the English Environmental Stewardship scheme. Journal of Applied Ecology, 49, 871-882
With nature conservation, we tend to think of the protection of rare and vulnerable species that are specialised or have uncommon ecological niches. However, recent decades have seen the demise of extreme generalists; species occurring under a range of environmental conditions which are able to proliferate very quickly. Farmland birds such as the skylark Alauda arvensis are a good example. Until recently this species was one of the most abundant breeding birds throughout Europe occurring in a wide range of habitats including arable land, dry and wet grassland, heathland and dunes. In the 1970s, this species was the most widespread and, next to sparrow Passer domesticus and blackbird Turdus merula, the most abundant breeding bird in the Netherlands (Bijlsma et al. 2001). Since then, however, their numbers have declined by more than 90% (Teunissen & Soldaat 2006) so that, although it is currently still quite common, the species has become a target of specific conservation efforts.
Halting the decline of such widespread species poses a serious challenge because conservation efforts cannot be targeted spatially to the species’ last bulwarks. In many European countries, agri-environmental programs have been designed to promote such widespread, declining species. Because these schemes have to be adopted by many farmers and over large areas, management prescriptions are generally simple allowing for easy incorporation in farming practices. So far, there has been very little evidence that these so-called ‘broad-and shallow’ schemes actually deliver conservation benefits and, when they do, they usually benefit species of low conservation concern (Kleijn et al. 2006). Furthermore, most studies have been executed at relatively small scales making it difficult to extrapolate results to national population trends (Kleijn et al. 2011).
In this issue of the Journal of Applied Ecology, Baker et al. examine how uptake of the English Environmental Stewardship scheme (ES) is related to changes in national farmland bird populations over the period 2002–2010.
The study examines whether landscape level population growth rates of farmland birds were associated with specific categories of ES management options. The authors find evidence for positive effects on biodiversity of agri-environment schemes implemented at the national scale. The study highlights that some forms of management, such as those targeting winter food supply of farmland birds, are particularly effective. Other types of management, such as those addressing breeding season population bottlenecks, did not have clear positive effects.
The results presented in this study are important because they are the first to provide evidence of ecological benefits of broad-and-shallow agri-environment schemes at a spatial scale relevant to policy makers. Conservation policy objectives are generally formulated at the national level, but until now no study has explored how local conservation efforts contribute to these objectives (Kleijn et al. 2011). By elegantly using results of a citizen science project (cf Silvertown 2009), the authors had a large enough sample size to test whether populations in landscapes with certain categories of management options differed significantly from populations in landscapes without agri-environment schemes.
This not only allowed them to test whether agri-environment schemes had positive effects, it also allowed them to examine whether this effect was large enough to offset the negative population trend shown by bird species in conventionally managed countryside. A second highlight of the study is that it identifies both effective and ineffective components of the English agri-environmental program for farmland birds. Such an evidence base is critical for further improvement of conservation management such as agri-environment schemes (Sutherland et al. 2004). The results stress the importance of winter food availability as a limiting factor for farmland birds and provides support for the hypothesis that a shortage of winter seed drives the population declines of most granivorous farmland birds (Gillings et al. 2005; Siriwardena et al. 2007).The lack of positive associations with measures aimed at improving breeding habitat might indicate that breeding habitat is not limiting, that measures did not effectively improve breeding habitat or that uptake was too low to result in significant population responses.
Like economies, ecosystems are exposed to pressures and drivers acting at different spatial scales. The effect of conservation management such as the Environmental Stewardship is moderated by factors such as climate change, spread of invasive species, land-use change or agricultural innovations. As these factors change, so will the efficacy of (parts of) the agri-environment schemes. Large corporations have entire departments devoted exclusively to research and development in order to be able to keep up with changing economic conditions. Likewise, monitoring and evaluation of the ecological impact of schemes is essential if we want schemes to (continue to) deliver the expected benefits. The current study is a good example of how this can be done both effectively and efficiently.
Bijlsma, R.G., Hustings, F. & Camphuysen, C.J. (2001) Algemene en schaarse broedvogels van Nederland 2). GMB Uitgeverij/KNNV Uitgeverij, Haarlem/Utrecht. (with English summaries)
Gillings, S., Newson, S.E., Noble, D.G. & Vickery, J.A. (2005) Winter availability of cereal stubbles attracts declining farmland birds and positively influences breeding population trends. Proceedings of the Royal Society B, 272, 733-739.
Kleijn, D., Baquero R.A., Clough, Y., Díaz, M., De Esteban, J., Fernández, F., Gabriel, D., Herzog, F., Holzschuh, A., Jöhl, R., Knop, E., Kruess, A., Marshall, E. J. P., Steffan-Dewenter, I., Tscharntke, T., Verhulst, J., West T.M., & Yela, J. L. (2006) Mixed biodiversity benefits of agri-environment schemes in five European countries. Ecology Letters, 9, 243-254.
Kleijn, D., Rundlöf, M., Scheper, J., Smith, H.G. & Tscharntke, T. (2011) Does conservation on farmland contribute to halting the biodiversity decline? Trends in Ecology & Evolution, 26, 474-481.
Silvertown, J. (2009) A new dawn for citizen science. Trends in Ecology & Evolution, 24, 467-471.
Sutherland, W.J., Pullin, A.S., Dolman, P.M. & Knight T.M. (2004) The need for evidence-based conservation. Trends in Ecology Evolution, 19, 305-308.
Siriwardena, G.M., Stevens, D.K., Anderson, G.Q.A., Vickery, J.A., Calbrade, N.A. & Dodd, S. (2007) The effect of supplementary winter seed food on breeding populations of farmland birds: evidence from two large-scale experiments. Journal of Applied Ecology, 44, 920-932.
Teunissen WA, Soldaat LL (2006) Recente aantalsontwikkeling van weidevogels in Nederland. De Levende Natuur, 107, 70–74 (with English summary)
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