The Structure and Dynamics of Agricultural Landscapes as Drivers of Biodiversity - Landscape Ecology for Sustainable Environment and Culture - page 276

14.1 Introduction
Agriculture and biodiversity are two faces of the same coin. On the one hand,
biodiversity is the basis of agriculture: plants that are grown, animals that are
raised are species shaped over centuries for the benefit of people; they all depend
on other living organisms. On the other hand, the fate of biodiversity in many
landscapes of the world depends on its use and management by rural/farming
communities. Some agricultural landscapes may be more diverse than ''natural
landscapes'' and thus are a source of biodiversity, but many farming practices at
field and landscape levels are a threat for biodiversity.
Between the 1960s and the 1990s the negative impacts of agriculture on bio-
diversity have become increasingly documented. Among the main drivers of
biodiversity decline are agricultural practices and changes in landscape structure
(Robinson and Sutherland 2002 ). For a long period, public policies neglected the
problem but then, under pressure from environmentalists and the general public,
regulations were established to protect rare or emblematic species. Nature reserves
were created and were extended to Natura 2000 zones in the European Union as an
ecological network of protected areas, designated to protect habitats and species
present on red lists in negotiations between NGOs and policy makers. Even though
farming techniques such as haying or grazing were used as integrative manage-
ment techniques for those protected areas, the general concept remained to seg-
regate the agricultural, productive areas from the nature protection areas (Fisher
2008 ). The growing insight regarding the benefits of ecosystem services led to an
interest in species providing those services and to the idea that biodiversity should
be managed and protected everywhere because it is of use everywhere. Nowadays
the maintenance of beneficial insects and birds, pollination, water purification etc.
are services that farmers must be aware of in their crop production and manage-
ment of land.
The objective of this chapter is to tackle these different issues. We utilize results
from the different projects carried out on a Long Term Ecological Research site,
the ''Zone Atelier Armorique''. Landscape ecology is the conceptual framework
we use. That is to say we consider landscape patterns, their heterogeneity and
connectivity, as major drivers of plant and animal population dynamics. Hetero-
geneity and connectivity are key concepts for biodiversity conservation and
management (Burel and Baudry 2003 ) that need to be defined as specific metrics
for the different questions and biodiversity groups we studied.
Landscape heterogeneity has many expressions. In the binary segmentation
between semi-natural and cropping areas, heterogeneity increases if the share of
the two components approaches 50 % of the area. The heterogeneity of the cul-
tivated mosaic is also an important expression. This mosaic can be highly heter-
ogeneous in space and time, as a result of the diversity of agricultural practices,
and their spatial and temporal organizations by farmers (Vasseur et al. in press ).
The diversity of agricultural practices (cultivated species and varieties,
rotations, technical operations) that can be observed at the landscape level, is due