Action: Increase the proportion of natural/semi-natural vegetation in the farmed landscape
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- Of four studies captured, one, a replicated and controlled paired sites study from Australia, found that farms with plantings of native vegetation held more species than those without. The effect was smaller than that explained by variation in the amount of natural habitat remaining on farms. A replicated study from Switzerland found more species in areas under the Ecological Compensation Area scheme than areas not under it.
- A before-and-after study from Switzerland found that the populations of three bird species increased after an increase in the amount of land under the Ecological Compensation Scheme. This study found that three species were more found more than expected on Ecological Compensation Scheme land. Another replicated study from Switzerland found that some habitats held more birds if they were close to ECA habitat but that the amount of Ecological Compensation Scheme in an area had no impact on population densities.
- A small study from the UK found no effect of habitat creation on grey partridge populations.
This intervention is concerned with general increases in the proportion of natural or semi-natural habitat in a landscape. Studies describing the effects of the creation of specific habitat types and the use of individual restored sites are discussed in ‘Habitat restoration and creation’.
Supporting evidence from individual studies
A before-and-after study in 6 km2 of mixed farmland in Switzerland (Spiess et al. 2000) found that the populations of corn buntings Miliaria calandra, whitethroat Sylvia communis common stonechat Saxicola torquata all increased following an increase in the proportion of land under the Ecological Compensation Scheme from 0.7% to 8.2% between 1992 and 1996 (corn buntings: six pairs in 1992 vs. 26 in 1996; whitethroat: 15 vs. 44; stonechat: 14 vs. 35). In addition, across 23 study areas in Switzerland, Ecological Compensation Scheme land and a 25 m buffer around it occupied only 17% of farmland but contained more (37-38% of 68) red-backed shrike Lanius collurio territories. Only 6% of Eurasian skylarks Alauda arvensis territories were found on Ecological Compensation Scheme land.
A small 2003 site comparison study of 20 farms in East Anglia and the West Midlands, UK (Browne & Aebischer 2003), found that the intentional creation of wildlife habitat had no discernable effect on autumn grey partridge Perdix perdix densities. The change in partridge densities from 1998 to 2002 on farms with habitat creation (-32% and -1%, respectively) was not statistically different from farms without habitat creation (-51% and -28%, respectively). Surveys of grey partridge were made once each autumn in 1998 and 2002 on 20 farms: 12 farms that created wildlife habitat and 8 farms which did not.
A 2007 site comparison study of 23 sites in the lowlands north of the Alps, Switzerland (Birrer 2007), found that the percentage of farmland designated as an ecological compensated area had no effect on the population density of farmland bird species or bird species with territories incorporating several habitat types. Ecological compensated areas are areas managed for the primary function of providing plant and animal habitat – these include meadows farmed at a low intensity. For 37 species surveyed in 1998/1999 and again in 2003/2004, population densities in wetlands and rivers were not affected by proxmity to ecological compensated areas, although hedges and traditional orchards close to ECAs did have higher bird population densities than those further away. Twenty-three out of one hundred hedges within ecological compensated areas had at least one of the 37 surveyed species present compared to 13 of 100 hedges outside the agri-environment scheme. The 23 selected sites (covering up to 3 km² each) were randomly selected and surveyed three times each between April and June in both years of study.
A replicated and controlled paired sites study in the springs of 2002, 2004 and 2006 and winter 2004 on 46 wheat and livestock farms across New South Wales, Australia (Cunningham et al. 2008), found that 23 farms with plantings of native vegetation had, on average 3.4 more bird species than farms without plantings. If farms had more than 20 ha of plantings then this increased to 4.4 more species. In addition, 12 native species responded positively to planting, and six responded negatively. However, three times more variation in bird community assemblage was explained by the presence or absence of remnant natural vegetation and the size of remnant patches than by plantings. Plantings were of both locally endemic and non-local (but native) species and were at least seven years old.
A 2007 site comparison study of 181 plots in the canton of Aagau, Switzerland (Roth et al. 2008), found that, on average, two more bird species were identified in ecological compensated areas (10 species on average) than in non-ecological compensated areas (9 species). Although on average two more bird species were found in the second set of surveys (carried out from 2001-2005) than in the first set (1996-2000), this increase was uniform in both ecological compensated areas and non-ecological compensated areas. One hundred and twenty 100 m radius circle plots that contained some land designated as an ecological compensated area were compared with 61 plots not containing any ecological compensated areas. The authors note that ecological compensated areas were typically established on promising farmland with the potential for “maximum biodiversity gain”, which may have affected the relative species richness of ecological compensated areas and non-ecological compensated areas.
- Spiess M., Marfurt C. & Birrer S. (2000) Ecological compensation - a chance for farmland birds? IFOAM 2000: the world grows organic, Basel, Switzerland 28-31 August 2000., 441-441.
- Browne S. & Aebischer N. (2003) Arable stewardship: impact of the pilot scheme on grey partridge and brown hare after five years.Final Report to DEFRA (Contract ref RMP1870vs3). DEFRA report.
- Birrer S., Spiess M., Herzog F., Jenny M., Kohli L. & Lugrin B. (2007) The Swiss agri-environment scheme promotes farmland birds: but only moderately. Journal of Ornithology, 148, 295-303
- Cunningham R.B., Lindenmayer D.B., Crane M., Michael D., MacGregor C., Montague-Drake R. & Fischer J. (2008) The combined effects of remnant vegetation and tree planting on farmland birds. Conservation Biology, 22, 742-752
- Roth T., Amrhein V., Peter B. & Weber D. (2008) A Swiss agri-environment scheme effectively enhances species richness for some taxa over time. Agriculture, Ecosystems & Environment, 125, 167-172