Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
Diversifying crop rotations with temporary grasslands - Université de ...
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2006; Makowski et al., 2007). Moreover, the highly productive regions or fields <strong>de</strong>dicated to<br />
<strong>crop</strong> production in the ‘land sparing’ strategy might be vulnerable to invasions of weeds, pests<br />
and diseases, and highly <strong>de</strong>pen<strong>de</strong>nt on external inputs and as they are lacking mechanisms of<br />
auto-regulation such as predation and competition provi<strong>de</strong>d by established communities of<br />
plants, animals and micro-organisms and other ecosystem services provi<strong>de</strong>d by biodiversity.<br />
The regions or areas of intensive conventional agriculture may thus present various ‘hid<strong>de</strong>n<br />
environmental costs’ and long-term risks (Van<strong>de</strong>rmeer and Perfecto, 2005).<br />
These two contrasting approaches of integration and spatial separation may both have<br />
important variations that are less consi<strong>de</strong>red in the literature. The ‘land sparing’ strategy may<br />
either consist of a separation between large nature reserves and highly productive regions<br />
where biodiversity and landscape diversity are largely eliminated (large-scale separation) or of<br />
rather small areas of non-<strong>crop</strong> habitats favourable to biodiversity [such as sown or natural<br />
field margin strips (Critchley et al., 2006), hedgerows, small forests or ponds] <strong>with</strong>in the<br />
landscape dominated by intensively farmed fields (small-scale separation, see illustration in<br />
Fig. 5 and <strong>de</strong>tails in Table 3). ‘Wildlife friendly farming’ may also be realized un<strong>de</strong>r various<br />
forms. However, it is usually thought to combine production and biodiversity at the same<br />
place and time (complete integration), which may be inefficient if the preservation of<br />
biodiversity requires high yield reductions, as pointed out by Green et al. (2005). However,<br />
there may also be an interesting and rarely consi<strong>de</strong>red variation of this strategy consisting in a<br />
temporal separation of the different functions.<br />
A.III.7 Temporal separation of farming and biodiversity?<br />
On the same field, periods of high yielding <strong>crop</strong> production may be alternated <strong>with</strong> phases<br />
favourable to different elements of farmland biodiversity at the scale of long <strong>crop</strong> <strong>rotations</strong><br />
(see Fig. 5 for an illustration and Table 3 for further characteristics). The phases favourable to<br />
biodiversity may either consist of less intensive <strong>crop</strong>ping (reduced inputs, reduced tillage,<br />
other <strong>crop</strong> types) or no production (such as rotational set-asi<strong>de</strong>), or periods in between the<br />
harvest and the sowing of the next <strong>crop</strong> managed so as to favour biodiversity (such as<br />
overwinter stubble fields, OSFs) (Smith et al., 1997; Moorcroft et al., 2002; Critchley et al.,<br />
2004). Many agri-environment schemes such as sown field margin strips are based on the<br />
spatial separation strategy and concern only a small fraction of land. This is probably one<br />
reason why positive effects on biodiversity are often limited (Kleijn et al., 2006; Liira et al.,<br />
2009). In contrast, actions implemented in the framework of the temporal separation may<br />
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