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