The ‘green revolution’ driven by plant breeding and chemical crop protection advances since the 1950s has enabled global food production, if not its distribution, to outpace human population growth for the past 50 years (FAOSTAT 2009). This has come at great cost to biodiversity, with severe losses across many taxonomic groups and a high proportion of the land surface (Foley et al. 2005, Millennium Ecosystem Assessment 2005). As early as the 1960s, the threats to wildlife of early generations of pesticides were immortalized in Rachel Carson’s (1963)Silent Spring, and other aspects of agricultural intensification continue to drive biodiversity loss today (Wilson et al. 2009). Bird populations are sensitive indicators of these effects (Gregory et al. 2005). In Europe, agricultural change continues to cause bird population declines (Donald et al. 2001, 2006, Newton 2004), and composite indicators of farmland bird abundance both in the UK (http://www.defra.gov.uk) and across Europe (http://www.ebcc.info) are at their lowest ever levels.
Against this backdrop of continuing biodiversity loss, humanity now faces the need for another green revolution. Driven by exponential growth in human population and economic aspiration, globalization of food markets, and the impacts of climate change on agricultural production across the world (Tilman et al. 2001, MacIntyre et al. 2009), security of food supply is now seen as one of this century’s greatest global challenges (Royal Society 2009).
There is growing consensus that further increase of agricultural production must be a ‘sustainable intensification’ achieved without further adverse environmental impacts and, wherever possible, reversing past losses (Firbank 2009, Royal Society 2009). Achieving this will necessitate valuation of the delivery of ecosystem goods and services (e.g. water yield and quality, soil function, carbon storage and biodiversity) and their integration with food production (Tilman et al. 2002, Firbank 2005, Robertson & Swinton 2005, Fischer et al. 2006, Pretty et al. 2006, Sukhdev 2008, MacIntyre et al. 2009). However, there is a real risk that bird conservation becomes peripheral to these considerations as we face an increasing preoccupation of agriculture with food production and its reconciliation with mitigating and adapting to climate change. Such a preoccupation is unsurprising given that agriculture already makes major contributions to greenhouse gas (GHG) emissions of both carbon and nitrogen (Vitousek et al. 1997, Steinfeld & Wassenaar 2007, Garnett 2009). Global growth in policy support for planting of bioenergy crops to mitigate GHG emissions, running well ahead of the evidence base on their net effectiveness in this regard (e.g. Cherubini et al. 2009), illustrates the importance of climate change and emerging policy responses as drivers of change. Similarly, the effects of climate change in increasing abiotic stresses such as drought, salinity and extreme temperatures are encouraging investment in new generations of transgenic crops (Wang et al. 2003).
This is a pivotal moment for bird conservation and agriculture in Europe. Shall we succeed in using what has been learned about the causes of loss of biodiversity from agricultural systems to ensure that bird conservation and recovery becomes a central concern of a sustainable intensification agenda? If we do, then perhaps 2010 (the year in which the EU target to reverse biodiversity loss will not be met in agricultural systems) may yet come to be seen as a turning point. If we fail, then the losses of the last 50 years will surely continue.
We have a solid foundation of knowledge on which to build: the proceedings of three recent British Ornithologists’ Union conferences addressing bird conservation in lowland agricultural systems, in 1999 (Aebischer et al. 2000), 2004 (Vickery et al. 2004) and 20091 testify to this. This growth in knowledge has been a crucial foundation of the greening of the European Union’s Common Agricultural Policy (CAP) through design and implementation of management measures in organic farming systems (Bengtsson et al. 2005, Hole et al. 2005), on land set-aside from agricultural production (Henderson & Evans 2000) and, especially, in agri-environment schemes. In the UK, for example, agri-environment management has reversed declines in the populations of several bird species of high conservation concern, including Corncrake Crex crex, Eurasian Stone Curlew Burhinus oedicnemus and Cirl Bunting Emberiza cirlus (Wilson et al. 2009). This combination of population monitoring, diagnostic research, testing and proving of management solutions, followed by successful incorporation into population-wide management schemes, is a notable success of applied conservation biology.
Given the high costs of agri-environment management across Europe (Kleijn & Sutherland 2003) and the continuing erosion of biodiversity in intensively managed agricultural systems, it is clearly important that the adaptive improvement of agri-environment management continues (Whittingham 2007). For example, in the cases of Corncrake, Eurasian Stone Curlew and Cirl Bunting in the UK, successful management has been developed from a strong evidence base, and been targeted efficiently at populations reduced to localized remnants. In contrast, national populations of more widespread and dispersed species such as Northern Lapwing Vanellus vanellus and Skylark Alauda arvensis continue to decline despite agri-environment intervention (Wilson et al. 2009). To extend success to species that have suffered severe declines but still occupy large geographical ranges needs renewed impetus to increase the scale of agri-environment implementation, to target implementation more closely (Evans & Green 2007), and to deliver the underpinning science to ensure that this is achieved cost-effectively. The balance of the science must therefore shift in emphasis from refinement on the management options in the agri-environment toolkit towards a better understanding of the spatial scale over which we need to deploy that management, and the degree of targeting necessary. For example, what combinations of magnitude of demographic effect and percentage of population benefiting from agri-environment measures will be sufficient to reverse a national population decline? Recent modelling studies (Vickery et al. 2008), and field experimental tests of the requirement for winter seed provision across intensive arable landscapes in Britain (Siriwardena et al. 2007) illustrate approaches that might be deployed, but a more concerted programme is needed.
It is also important to devote more attention to the remaining lower-intensity livestock systems that continue to support a rich biodiversity across Europe (Bignal & McCracken 1996). Here, agriculture is often economically marginal, and the risk is often more of agricultural abandonment than of intensification. Agri-environment resources may be critical to maintain a system that is already broadly supportive of wildlife of high conservation concern rather than to buffer against any risk from intensive production. An improved understanding of the resources offered by these ‘High Nature Value’ farming systems may increase the effectiveness of agri-environment management in these systems, and assist efforts to move subsidy support from being predicated on compensating agricultural disadvantage to providing active support for the maintenance of environmentally beneficial farming systems and practices (Swales & Moxey 2008). A better understanding of the mechanisms through which certain low-intensity agricultural systems continue to support very high densities of some bird species may also offer important insights into management to help restore these species to areas of more intensive agricultural production.
Advances in all these areas are needed urgently to inform current debate over the future of the CAP, particularly the balance between Rural Development funding and the Single Farm Payment, and the future scope and size of the Agri-environment Measure within the next Rural Development Programme.
More generally, we need to understand whether existing management for bird conservation in agricultural systems is consistent or in conflict with the delivery of other ecosystem goods and services. The long-term sensitivity of global agricultural production to biodiversity of pollinators (e.g. Aizen et al. 2009), and the delivery of reduced production costs, net carbon emissions and soil erosion, but increased nutrient recycling and soil biodiversity through conservation tillage of arable soils (Holland 2004, Lal 2004, Smith 2004) are examples of synergies. There is also growing evidence that creation of agriculturally managed wetlands for water and pollution management purposes can deliver biodiversity benefits (Bradbury & Kirby 2006, Thiere et al. 2009), and in economically marginal agricultural landscapes of high nature value, wildlife can deliver tangible economic benefits through tourism (e.g. MacMillan et al. 2004, Dickie et al. 2006). In intensive production systems, field margin managements are now a core element of agri-environment management for birds, mammals, invertebrates and wild flora across Europe (e.g. Vickery et al. 2009), and more studies are needed to assess their actual and potential contribution to delivering other services such as GHG mitigation, water quality and pollination (e.g. Kohler et al. 2007). We also need to explore in more detail the spatial grain at which trade-offs between the commitment of land to production and to the delivery of environmental goods might best be made. For example, at the field scale, withdrawal of synthetic pesticide and fertilizer inputs by organic farming systems provides opportunities to integrate production, wildlife conservation and other ecosystem services such as carbon sequestration within individual cropped fields, but this may sometimes come at the cost of lower yields from those fields (Lotter 2003). Much agri-environment management in non-organic systems has, in contrast, tended to concentrate on field margins and boundaries, with fewer managements impinging directly on field centres during the growing season. The studies by Morris et al. (2004) of managing the structure of autumn-sown cereal fields for Skylarks, and by Chamberlain et al. (2009) of the benefits of establishing in-field fallow plots for Northern Lapwings are notable exceptions. At coarser spatial grains, we still know little about the added benefits that may be gained from larger, contiguous areas (multiple farms) under organic or agri-environment management (Gabriel et al. 2009). Equally, the proposition that agri-environment management can ‘soften’ the agricultural matrix sufficiently to increase functional connectivity of patches of semi-natural habitat (Donald & Evans 2006) requires further testing across taxa. At the landscape scale, reversing the fragmentation of extensively grazed systems such as heathland, saltmarsh and floodplain wetlands may be critical to give these habitats greater resilience, while also offering opportunities to deliver other ecosystem services such as flood risk mitigation and reversal of soil carbon losses (Sutherland 2002, 2004). However, we need to know more about the optimum spatial configuration for such restoration, which may of course come at the expense of some loss of agriculturally productive land.
In reality, restoring ecological heterogeneity in agricultural systems by making space and time for the life cycles of non-crop organisms is likely to be needed across spatial scales from the field to the catchment or ‘landscape’ (Benton et al. 2003, Firbank 2005, Tscharntke et al. 2005). The long-term sustainability of a new green revolution will depend on breaking down the cultural and political barriers to recognition that the long-term stewardship of agricultural landscapes requires integration of food production with the delivery of environmental goods and services. In the words of the UK Government’s Policy Commission on the Future of Farming and Food (2002), the agriculture industry will then have ‘embraced the management of the land for environmental public goods as a key part of what farming is about’. This integration is essential and urgently needed, both from an ecological perspective, as the continuing declines of farmland bird populations illustrate, but also for the long-term sustainability of agricultural production. As Rachel Carson knew, success will, in part, be measured by birdsong, and failure by its absence.