The Agriculture and Conservation Paradox
Few human activities are as paradoxical as agriculture in terms of their role for nature conservation. Agricultural activities are the major cause of negative environmental change worldwide. For instance, agriculture: is the main cause of deforestation; is the major threat to bird species; accounts for ca. 12 % of total direct global anthropogenic emissions of greenhouse gasses; and strongly impacts on soil carbon and nutrients (sources of evidence in Rey Benayas and Bullock 2012). In recent history, in addition to an increase in farmed area, farming practices in many regions have become more intensive. For example, the area of cultivated land serviced by irrigation, the major form of human water consumption and a surrogate of farmland intensification, in Europe increased from 9.2 × 106 ha in 1961 to 17.9 × 106 ha in 2011 (FAOSTAT 2013). Beyond changes in species richness, agricultural intensification has been shown to reduce the functional diversity of plant and animal communities, potentially imperilling the provisioning of ecosystem services (Flynn et al. 2009). Importantly, intensification of land use has brought remnant areas of natural or semi-natural vegetation such as steep hillsides, property boundaries and track edges into mainstream agriculture (Rey Benayas et al. 2008). Thus, agricultural expansion and intensification have greatly increased our food, fiber and biofuels supplies, but have damaged wildlife and other services.
In contrast to these negative perspectives, extensive agricultural habitats are often viewed positively in terms of nature conservation due to, for example, creation of landscape mosaics and environmental heterogeneity (Oliver et al. 2010), or because they are threatened habitats that support endangered species and cultural values (Kleijn et al. 2006). In the EU-27, 31 % of Natura 2000 sites, a network of protected areas, result from agricultural land management. Several taxa including species of birds, insects and plants, some of them endangered, depend on low-intensity farmland for their persistence (Kohler et al. 2008). Thus, common farmland birds in Europe show negative trends (−35 % since 1980) and these are today of conservation concern, whereas forest birds show positive trends due to abandonment of agricultural land and afforestation programs (European Bird Census Council 2010). Wildlife decline might affect agricultural production itself. For instance, insects that
Fig. 7.1 Sketch of a hypothetical Mediterranean agricultural landscape before ( top) and a few years after ( bottom) implementing strategic revegetation actions. The actions illustrated are the following: (1) introduction of woodland islets and (2) hedgerows in cropfields; (3) restoration of riparian vegetation; (4) revegetation of road sides and (5) roundabouts. Additionally, there are some (6) abandoned fields, which are indicated by arrows. The lack of revegetation actions in the bottom left quarter of the landscape illustrates the inappropriateness of such revegetation due to e.g. outstanding values linked to steppe birds. Establishment and development of vegetation following cropland abandonment is different in fields close ( blue arrows) or away ( red arrows) from strategic revegetation actions or natural vegetation
provide pollination and pest control services in cropland tend to be less common in more intensive landscapes (Tscharntke et al. 2005).
Agricultural intensification can have a negative impact on the values linked to traditional agriculture, but so can agricultural abandonment and, particularly, when afforestation occurs on former cropland (Rey Benayas et al. 2007). Abandonment of agricultural land has mostly occurred in developed countries in the last few decades (Rey Benayas and Bullock 2012). The European Agrarian Policy has aided afforestation in agricultural land that has resulted in the convesion of > 106 ha of former cropland into tree plantations (Directorate-General for Agriculture and Rural Development 2012). Currently, it is providing subsidies to afforest land after vineyard extirpation in Spain, for instance, an action that is being criticized by conservationists due to negative impacts on wildlife and other values (Rey Benayas and Bullock 2012). It seems that agriculture, woodland, and biological conservation are in a permanent and irreconcilable conflict, the agriculture and conservation paradox (Rey Benayas et al. 2008).