• Reduce text

    Reduce text
  • Restore text size

    Restore text size
  • Increase the text

    Increase the text
  • Print

    Print

The biodiversity of farmland birds: intensive farming and its spatial distribution have important effects on bird communities

Reconciling biodiversity and agriculture thanks to agri-environmental measures is central to numerous debates. INRA scientists and their colleagues have shown that the effects of intensive farming on the biodiversity of farmland bird communities are increased by its structure.  Thus grassland specialist birds are more affected by intensive farming when it is homogeneous.  These are important results if we are to improve the efficiency of environmental measures.

The woodlark or wood lark (Lullula arborea) is the only species in the lark genus Lullula. It breeds across most of Europe, the Middle East, Asia and the mountains of North Africa. © Ján Svetlík. Licensed under CC BY-SA 2.0
Updated on 09/02/2016
Published on 11/12/2015
Keywords: biodiversity - bird

Although the intensification of farming has played a crucial role in increasing food production during recent decades, it has also caused environmental damage, which has notably affected the biodiversity of farmland birds.  At present, farming needs to resolve a complex equation: to meet growing demands for food while improving its environmental impact and sustainability.  INRA scientists and their colleagues have explored the link between the spatial distribution of the intensity of farming and biodiversity.  Understanding changes in biodiversity as a function of this intensity is essential if we are to determine where agri-environmental policies will be the most efficient. 

The scientists worked on the whole of mainland France at the scale of 152 small agricultural regions (SAR), coupling databases describing both agriculture and farmland birds.  They thus characterised agricultural intensity using an indicator based on input costs per hectare with particular focus on five farming systems -  industrial crops, cereals, dairy cattle, beef cattle and mixed arable/livestock farms - representative of farming activities accounting for the majority of French farms (67%) and covering more than 80% of agricultural land.  They also described communities of birds - involving a total of 22 species - using four levels indicative of their size (species richness) and their composition (specialisation of the community to farmland, trophic level and specialisation to grassland habitats). 

Agricultural intensity affects the composition of bird communities...

The scientists thus evidenced that the intensity of agriculture has a greater effect on the composition of the bird community in a small agricultural region than on its size.  The three levels that characterise its composition (trophic level, specialisation to grassland habitats or specialisation to farmland) were all affected, thus revealing that all species are not equal within a bird community.  In some species, a slight increase in agricultural intensity causes a marked loss of diversity, so they will be disadvantaged.  On the other hand, other species may be favoured, and their importance within the community will increase up to a certain threshold.  The former group of species, such as the meadow pipit, yellowhammer, wood lark, red-backed shrike or the hoopoe, prefer grassland where they eat invertebrates, and dominate the community in regions of extensive agriculture.  The latter species, such as the partridge, yellow wagtail or corn bunting, are lovers of grain and prefer cultivated land.  They replace the disadvantaged species in regions of more intensive agriculture.

…and its spatial distribution enhances this effect

As a second stage, the scientists examined the effects of the spatial structure of agricultural intensity on bird communities.  For some groups of species, such as grassland specialists, the homogenisation of intensity between neighbouring SAR increases its effect.  The response of these species to intensive agriculture is stronger in SAR surrounded by SAR of similar intensity than in those surrounded by SAR of a different intensity.

These findings suggest that measures to promote extensification may be more effective in areas where intensity is moderate and homogeneous between SMA.  Encouraging a dispersion of intensity in regions of high intensity may constitute another lever to benefit species that are disadvantaged by intensity. 

Overall, this work and its results argue in favour of an indicator which combines the different facets of agricultural intensity and thus a robust statistical model that could predict the composition of a bird community depending on agricultural intensity.  They reveal the effect of intensive farming on the biodiversity of bird communities, linked to the spatial structure of this intensity.  Finally, they offer interesting perspectives to adjust and improve the efficiency of agri-environmental policies in favour of biodiversity, not only as a function of context but more generally at a national scale.

The intensity of agriculture, in practice

The intensity of agriculture is characterised by an increased productivity of cultivated land.  This can be evaluated by counting up the inputs used for the production process or the yields thus generated.

During this study, the authors used an input-based measurement tool (expenditure on inputs) using the ratio between expenditure on different types of input and the usable agricultural area (input costs, or IC/ha, expressed in €/ha).  The inputs taken into account included a breakdown of expenditure on fertilisers, animal feeds, pesticides, seeds, fuel, veterinary products and irrigation water.

The national mean value of this ratio is €405.1/ha.

Reference

Félix Teillard, Frédéric Jiguet and Muriel Tichit. March 23, 2015. The Response of Farmland Bird Communities to Agricultural Intensity as Influenced by Its Spatial Aggregation. PLOS ONE DOI:10.1371/journal.pone.0119674.