Introduction

Changes in agricultural systems through the process of globalisation and the need to increase farm productivity over the past few decades have led to dramatic land-cover changes as well as the introduction of new technologies that are major threats to biodiversity in many parts of the world (Donald et al., 2001; Norris, 2008). Loss of biodiversity is a global concern for many reasons. The first is that the loss of a species is a non-reversible process; this has led to Nature Conservation treaties and policies at world and national scales. The second reason is that species must be protected not only for their intrinsic value, but also because of the services they provide to society. The Millennium Ecosystem Assessment (www.millenniumassessment.org) has emphasised the latter aspect, and ‘ecosystem services’ (Carpenter et al., 2007; Zhang et al., 2007) is now a key word on many agendas, whether in the realm of nature protection or landscape management. From this perspective, the main cause of biodiversity loss is an overemphasis on production services (food and fibre) at the expense of other services such as water purification, pest control or pollination. The two main proximal causes that lead to loss of species are habitat loss (transformation of natural or semi-natural habitats to arable land) and heavy use of energy in the form of mineral fertilisers, especially nitrogen, pesticides and soil tillage (Matson et al., 1997). All have adverse effects, though they may favour some species that become pests.