Diversifying crop rotations with temporary grasslands - Université de ...

Declines in weed diversity may have severe impacts on many other organisms (various types
of animals and micro-organisms) that are using weeds either as hosts or food resources
(Gerowitt et al., 2003; Marshall et al., 2003; Holland et al., 2006; Storkey, 2006). Weeds may
therefore be well suited as indicator organisms for farmland biodiversity in general (Albrecht,
2003). A large panel of different organisms may depend on weeds including herbivores,
pollinators, seed eaters, and decomposers as well as organisms at higher trophic levels of
many different taxonomic groups, e.g. arthropods (Norris and Kogan, 2005). Birds attracted
the most attention. During the last decades, farmland birds showed dramatic populations
decreases in many European countries (Krebs et al., 1999; Bretagnolle, 2004; European Bird
Census Council EBCC, 2008), which was much stronger than for any other group of birds
(Fig. 1). Of the 195 bird species with an unfavourable conservation status in Europe, 116 are
farmland birds (European Bird Census Council EBCC, 2008).
Fig. 1: Population trends of common bird species in Europe.
The graph (taken from the European Bird Census Council EBCC, 2008) shows an index of the average breeding
population densities of 36 common farmland bird species (red line), which decreased by about 50% from 1980 to
2006, while all common birds (black line) and forest birds (blue line) declined by only 10%. Shown are weighted
geometric means from 21 European countries (Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Netherlands, Norway, Poland, Portugal, Spain,
Sweden, Switzerland, United Kingdom) that were compiled by the Pan-European Common Bird Monitoring
Scheme (PECBMS), a common initiative of the EBCC, the Royal Society for the Protection of the Birds (RSBP),
BirdLife International, and Statistics Netherlands.
These strong declines of farmland birds were probably caused by habitat destruction and food
shortages linked to agricultural intensification (Fuller et al., 1995; Siriwardena et al., 2000;
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