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

2007). Agriculture is increasingly dependent on limited fossil resources to produce the
fertilizer, pesticide and water inputs and to run the farming machinery. Pollution by pesticides
and fertilizers may have negative effects on ecosystems and humans (Huber et al., 2000).
Agriculture is also an important driver of climate change. In 2004, it caused about 14% of the
worldwide human greenhouse gas emissions (mainly CH4 and N2O), the 14% do not include
the CO2 emitted due to the use of fossil fuels (IPCC, 2007, Figure TS.2b). Land use change
including the deforestation for agriculture accounted for an additional 17% of anthropogenic
greenhouse gas emissions (mainly CO2) in 2004 (IPCC, 2007, Figure TS.2b). It is estimated
that soils of agricultural ecosystems have lost between 50% and 75% of their antecedent
carbon content (Lal, 2007). Since 1850, about 35% of the anthropogenic CO2 emissions
resulted directly from land use (Foley et al., 2005). Finally, land use change (including the
conversion of natural areas and agricultural intensification) is thought to be the most important
driver of the observed global biodiversity loss, even before climate change, nitrogen
deposition and biotic exchange (invasions of exotic species) (Sala et al., 2000). In Europe,
both the intensification of farming practices as well as the abandonment of agriculture in other
regions are both big threats to biodiversity at different levels (genes, species, ecosystems),
including the ‘wild’ species typical for farmed landscapes (van Elsen and Günther, 1992;
Matson et al., 1997; Krebs et al., 1999; MacDonald et al., 2000a; Stoate et al., 2001;
Bretagnolle, 2004) and the domesticated species, varieties or races of crops and livestock. The
loss of both ‘wild’ and ‘domesticated’ biodiversity (often also called ‘associated biodiversity’
and ‘agrobiodiversity’, respectively) may have various negative consequences. Besides
aesthetic, moral and ethical/religious reasons, biodiversity is needed to maintain important
ecosystem functions and services (reviewed in Chapin et al., 2000; Hooper et al., 2005; Diaz
et al., 2006). This includes nutriment cycling, pollination and pest control, thus also direct
benefits for crop production (Altieri, 1999; Swift et al., 2004; Clergue et al., 2005; Berger et
al., 2006; Albrecht et al., 2007; Moonen and Bàrberi, 2008). The chemical and genetic
resources of many ‘wild’ organisms may also be used for the production of food or
pharmaceutics and for crop and livestock breeding. Finally, there are more general benefits of
biodiversity to human well-being, which are increasingly recognized (MEA, 2005; Diaz et al.,
2006).
The challenge of modern agriculture is thus to reduce its negative impacts on the environment
and on biodiversity as well as the reliance on external inputs while maintaining or further
increasing its productivity on the short and long term (Tilman et al., 2002; Tybirk et al.,
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