1
Globalisation and the sustainability of agricultural landscape system; Jørgen Primdahl & Simon Swaffield (Eds) CAMBRIDGE UNIVERSITY PRESS (version Feb, 10, 2009)
Agricultural landscape changes through globalisation and biodiversity effects
Jacques Baudry1, Santiago Poggio2, Françoise Burel3, Catherine Laurent4 1: INRA, National Insitute for Agronomic Research, UP 980 SAD-Paysage, CS 84215, 35042 Rennes Cedex, France (
[email protected]) 2: University of Buenos Aires, CONICET-Cátedra de Producción Vegetal, Facultad de Agronomía, Argentina 3: CNRS, National Center for Scientific Research, UMR Ecobio, Université de Rennes 1, Rennes, France 4: INRA, National Insitute for Agronomic Research, UMR SAD-Apt, Paris, France
Introduction
Changes in agricultural systems through the process of globalization and necessity 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 the intrinsic value, but also because of the services they provide to society.
The
Millennium Ecosystem Assessment (www.millenniumassessment.org) has emphasized 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
2 overemphasis on production services (food and fiber) 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 form of mineral fertilizers, especially nitrogen, pesticides and soil tillage
(Matson et al. 1997). All have adverse effects, though they may
favor some species that become pests.
To understand changes in the various relationships between agriculture and biodiversity, it is necessary to have a conceptual framework through which to analyze the different changes in the diverse regions of the world, and to look at the way that research might help policy makers. The aim of this chapter is to provide insights on these two issues. The chapter first sets out a framework of analysis based upon landscape ecology. We then offer two comparative and linked case studies. We use Brittany, France and the Rolling Pampa of Argentina as an empirical basis for three main reasons: they represent extreme situations in terms of policies; they are in different biogeographical zones, and are linked through trade. Argentina has a totally free market policy on agriculture, while France, being part of the European Union, has strong public agricultural policies, with subsidies and growing environmental regulations, and thus both sit on quite different parts of the policy spectrum described in Chapter One. In Argentina, the pampas were grassland before the introduction of agriculture two centuries ago, whilst in Brittany, agriculture started over 5000 years ago through forest clearance. The cases are functionally linked because since the end of World War 2, intensive animal production systems in Western Europe and especially in Brittany had to rely on the import of proteins (soybeans) from America (Bertrand et al. 1985), mainly USA in the sixties, then South America, in particular Argentina. Following the case studies, we reflect upon some lessons and implications for science and policy.
The conceptual framework
3 Landscape ecology provides the conceptual framework for our analysis for several reasons. The first is that landscape composition and patterns are a better predictor of species present and biodiversity parameters in general than plot/ field scale approaches (Le Coeur et al. 2002; Burel and Baudry 2003); the second is that because landscape ecology explicitly addresses the causes of landscape heterogeneity and changes, it considers human activities as part of the system. Landscape ecology also provides an hierarchical view of both the components and the factors driving biodiversity, which allows understanding of how human activities from field to global scale affect biodiversity, and at which scale to manage the relationships (Burel and Baudry 2003).
Fields are the basic common elements to both ecology and social sciences; they are the habitats of plants that furnish biomass and shelter to animals, and one of the basic units considered by for farmers for decision making. On the social side, fields are parts of farms that are not necessarily continuous in space. Farmers make decisions regarding the type of production and the technical means to achieve their objectives within a set of internal (farm characteristics) and external constraints (market, available technologies, policies). As other chapters of the book illustrate, policy makers operate at all scales from the municipality to the world level. Relationship between agriculture and environment is discussed at various levels were contradictory positions are expressed as shown in the debate concerning the multifunctionality of agriculture (Laurent 2001). The flow of policy information between the different levels goes both ways, bottom up as decision makers from one level gather to make collective decisions (at least supposedly collective) up to institutions such as the WTO, and top down, afterwards, to integrate at lower levels the rules that were agreed on at a higher level.
On the ecological side, fields form the land cover mosaic, and, with the associated field boundaries and non-agricultural landscape elements, the landscape mosaic. Landscape composition and structure drive biodiversity components in different ways. Landscape composition determines habitat types (grassland, woodland, cropland, road verges) and
4 their size. Habitat fragmentation is an important issue: generally, smaller habitat patches harbor less species than large ones, depending on the species requirement in term of movement, food and population size, to allow reproduction. Two important concepts in the analysis of the landscape mosaic from a species point of view are complementation, which is the fact that a species requiring different types of habitat during its life cycle or from season to season will seek
these habitats within its range of movement,
and supplementation, which is the possibility for a species to use several patches of the same habitat to sustain its life. Because of the diversity of land uses in agricultural landscapes, habitats are typically fragmented, but patches of similar habitats are not far apart.
Landscape connectivity is a topic widely studied and debated in landscape ecology. It is used to develop and justify policies related to the implementation of “corridors” to facilitate species movement across landscapes. Farmland is a barrier for forest species, but low input farmland can support many species and permit their movement. For aquatic ecosystems, the presence of buffer zones that disconnect them from the surrounding terrestrial environment is often crucial for their quality. These buffers can be the riparian wetlands, hegerows, grassy strips (Sabater et al. 2003; Lee et al. 2004). The figure 1 gives a schematic representation of changes occurring in a hedgerow network agricultural landscape. In A, networks of hedgerows insure a high degree of connectivity for species that cannot thrive in fields. Some hedgerows are parallel to the stream corridor in the center, acting as buffer. Field enlargement with no consideration of these functions, in B, lead to isolated hedgerows and a direct connection between the stream corridor and the upland. It is no the quantity of hedgerows, per se, that matters, but the structure of the network, the design of the landscape.
In agricultural landscapes, the question of land management/use is a crucial object, as it is on privileged object to analyze the level of input (fertilization, pesticide application) and mechanical disturbances (mowing, plowing). Therefore, habitat quality may vary
5 within as among crops or grassland. Changes in crop management are the key of most agri-environmental schemes. The land use mosaic that determines landscape patterns is a product of human decision, within the physical constraints of the area (climate, geomporphology). In agricultural landscapes, the proximate factors driving those decisions depend on farm structure (size etc.) and farmers objectives. Farmers also behave according to overall objectives such as global income of the household in family farms, land tenure constraints, market and policy decisions as well as available technology. As highlighted in other chapters in this volume, policies, market and technologies are worldwide phenomena. Ultimately, our comparative cases study shows how the fate of biodiversity in a given landscape is, in part, dependant upon global processes.
Hierarchy theory is one of the components of the development of landscape ecology (Allen and Hoekstra 1992). It enables analysis to link processes occurring at different scales. On the biological side, the hierarchical structure is composed of the habitat embedded in the landscape mosaic, itself in a biogeographic region that set the species pool that evolve under the regional conditions. As we show, the pool of species is also dependant on movement of goods and humans across the globe; species moving from one biogeographic area to another are called alien, they can outcompete local species, thence being an ecological problem. On the human side, for a question such as hedgerow management, farmers as agents respond to a range of factors and imperatives at a local scale (aesthetic characteristic of the landscape, relation ship with neighbors), in terms of their farm and community, at a district and regional scale, in terms of conservation planning regulations for example; they are influenced by economic and environmental policy at a national scale (national agri-environmental regulation); and by commodity and energy markets at a global scale (relative price of fire wood). The biotic and social hierarchies therefore interact at all scales. These interaction must be analyzed for designing relevant policy measures.
6
The Brittany case study Brittany is a peninsula at the NW corner of France, on the Atlantic Seaboard. It is an ancient bedrock of shale and granit, with loess deposit on the northern coast. The relief is smooth. Average rainfall varies from 600 mm on the coast to 1500 mm in the center; freezing days are scarce, the average minimum temperature is 6°C in January; summers are mild (18-19°C in august). The Brittany landscape is dominated by agriculture, forest covering 12 %. The dominant crops are rotational grassland, maize and cereals. The presence of hedgerows as field boundaries is a cultural feature with many ecological roles (Baudry et al. 2000a). It is a region of intensive farming, mainly dairy cows and hogs, and poultry; these animal are largely fed with imported feedstuff (soybean, manioc etc.).
In Brittany, as in most of Eurasia, the clearing of forest for agriculture started more than 5000 years ago, as shown by pollen records (Gaudin et al. 2008). These records also show that land was, in many places, successively cleared and then abandoned during war or epidemic events. Therefore, the flora and fauna that is currently present has been selected and shaped by the many cycles of human activity over time. For both plants and animals, many species need an agricultural environment to thrive: grassland species and weeds are such examples. The high level of heterogeneity of ecological conditions resulting from farming practices in small farms and, overall, the presence of dense hedgerow networks has historically promoted species rich landscapes.
A decline in the total number of plant species started as early as the eighteen century with changing technology and practices, and species loss accelerated with the advent of fossil fuel based agriculture. This so-called intensification of agriculture has many facets: the use of energy to move large machines, the production of artificial fertilizers, and use of chemical pesticides. Starting in the 1960’s, the Common Agricultural Policy (CAP), set up by the first six members of the European Union, aimed at providing cheap and
7 abundant food to European consumers and agro-industries. The prices of several commodities (milk, wheat, meat) were guaranteed by the Common Market. Price regulation was part of a wider modernization policy that included the development of credit facilities (to secure access to capital), of extension services (to secure access to knowledge) and the improvement of farm structures (to secure access to land). It leaded to a strong intensification of production systems with heavy investments in machines and inputs. According to countries and regions, it was declined in different ways Small scale farms were unequally targeted but in a region such as Brittany there were the basis of the modernization scheme. This modernization strategy took advantage of the availability of jobs in industry and increasingly accessible urban areas which led to part of the smaller farmers, and even more so their children, to quit their farms and turn to nonagricultural employment. This process led to the disappearance of many farms and mean farm size increased, and is still increasing. Farm enlargement has important consequences for landscape patterns, fields are enlarged, semi-natural elements (hedgerows and other field boundaries) were removed. However, the average agricultural area of farms in Brittany remains small and farmers who want to make a living out of their holding need a high productivity per hectare.
Analysis of biodiversity trends in the agricultural landscape must consider two correlated phenomena: simplification of landscape patterns and higher inputs. A third factor also plays a role, whatever the landscape situation: that is, a decrease in crop diversity (crops like Lucerne, clover, oat, barley, beets are no more grown), further reinforcing the loss of landscape heterogeneity, which is a key for biodiversity (Benton et al. 2003). Currently three types of crops (wheat, maize and sown grasses represent 87% of arable land which is 86
% of farmland).
An assessment of the relationships between farming systems and biodiversity in Brittany has been undertaken on the Pleine-Fougères Long Term Ecological Research site (www.caren.univ-rennes1.fr/pleine-fougeres). It is composed of a gradient of landscapes
8 characterized by a variation of hedgerow density (Baudry et al. 2000b) which in 1994 varied from 260 m/ha to 100 m/ha from south to north. When the investigation started in the mid 1990’s, part of the area, the south, was still used by small family farm (less than 20 ha) with low production systems, while the northern part was dominated by large (more than 50 ha), productive farms. Hedgerows and field margins in the south were managed in a “traditional” way, mowing being the dominant technique. In the north, herbicide was widely used. This contrast within a small area (100 km²) which is quite homogeneous in terms of abiotic factors permitted analysis of differences in species distribution due to differences in landscape structure, with associated differences in farming systems (Burel et al. 1998).
No difference was found in composition of some groups of species (small mammals, woody plants), while there was a net loss of other species (small flies); in a third group (carabids, herbaceous plants), changes in species composition were noted, while the number of species was stable. The general trend was that going from a dense, low input landscape to an open high input landscape, habitat specialists (mostly linked to stable habitats as hedgerows) disappeared, while generalist, widely distributed species became frequent. Further analysis showed that the diversity of farmers is an important factor for plant distribution (Le Coeur et al. 2002) and that there are strong interactions between landscape structure and field margin management in the control of species distribution. High levels of disturbances (such as cultivation) and high fertilization levels favor annual plants that are mostly weeds and nitrogen demanding species (e.g. nettles, brambles etc.), that are common, at the expense of less frequent species that thrive in nutrient poor habitats.
Aviron et al. (2005) show that the carabid species Abax Parallelipipedus is favored by a high density of hedgerows, and that herbicide application or grazing of field margins deplete the populations sizes; they are higher when management is scarce. The analysis of a 2007 sampling of carabids in the same landscapes shows a strong effect of crop
9 successions: the more frequently the grass is the land cover, the more abundant Abax are, still in dense hedgerow networks (Goffi, Vasseur, Baudry, unpublished). These results epitomize the complexity of designing policies to protect biodiversity. In many European countries, policies aim at protecting and planting hedgerows, while the Common Agricultural Policy has agri-environment schemes mostly aiming at adapting land use practices to biodiversity objectives at field scale. These schemes are short term (5 years) and cannot integrate crop succession, nor landscape design; the absence of the latter, because contracts are at field scale, may be a cause in the lack of positive effects of these schemes (Kleijn and Sutherland 2003). Biodiversity must be managed at different scales from field to landscape, i.e. across farms; but as ecosystem service contracts are typically at a farm scale, little collective management is possible.
Stream biodiversity is also affected by landscape patterns (Sarriquet et al. 2006) and nitrogen leaching from fields that are over fertilized, often with manure; excess fertilization for nitrogen varies from 30 to 100 kg/ha/annum in Brittany. Hedgerow removal also causes the arrival of more sediment from field erosion. The ecological condition within small, first order, streams mostly depends upon adjacent land use, while more important stream integrate landscape and land use of the whole watershed.
Overall, the Brittany case study shows that farmers react very rapidly to new incentives, either from policies or from technology. Changes in biodiversity, species loss and replacement, is also very rapid, in a few years changes are significant. The spatial heterogeneity of changes is also a fact, not all farmers in area change at the same pace and very local social interactions may be important as a control of changes. This means that the between landscape diversity must be considered in environmental management.
The Pampean case study
10 The Pampas of Argentina are one of the most productive areas of agricultural commodities in the world,
due to favourable climate, fertile soils, and low population.
Furthermore, farmers and agronomist proactively implement new technologies when they found them suitable for increasing crop yield and farm income. Adoption of glyphosate resistant GM-soybean is a paradigmatic example. When released in 1996, only 5% of the soybean crops were GM varieties, but by 2001 they exceeded 90% (Fig. 2). Despite the benefits for Argentine economy, GM-soybean expansion has caused concern about its environmental impact. However, Argentina lacks active policies aiming to reduce the negative effects of agriculture intensification and to restore rural landscapes, even though there is legislation about these issues. GM-crop expansion in the Pampas, because of its complexity and the numerous facets involved, is an interesting case for studying how fast technological changes in farming systems may alter landscape configuration, and therefore, ecological processes maintaining the biodiversity of agroecosystems. The analysis will be focus on the Rolling Pampa, a sub-unit of the Pampas having the longest history of landscape transformation by human activities (Soriano 1991), and where agriculture effects on biodiversity have also been studied for sufficient time, particularly those on natural grassland and weed assemblages (Soriano 1991, Ghersa & León 1999).
The Rolling Pampa is delimited by Paraná and de la Plata rivers on the north-east, whereas the Salado river sets the south-western limit with Flooding Pampa (Soriano et al. 1991). Topography is gently undulated and crossed by streams. Climate is temperate and humid, with hot summers and a dry season that is not marked. Rainfall averaged 1000 mm per year and mean annual temperature is 17°C. Soils are mainly Mollisols, which are characterised for the surface horizon rich in organic matter, fertile, and porous that determine the excellent aptitude for agriculture. Extensive grasslands without trees and open horizons characterised the Rolling Pampas when Spanish conquistadors arrived in the 16th century. Structure of pristine vegetation changed with water availability, being a prairie during humid periods and a pseudo-steppe in dry years (Soriano 1991). Original
11 grassland landscape has been completely transformed by agriculture and fragmented by corridors.
Grasslands of the Rolling Pampa have been transformed by human activities for more than 400 years, which induced changes in landscape structure and groundcover patterns and dynamics. Replacement of grassland by sown field crops has been the main transformation of land cover. Farms have become more specialised in growing few crops, and livestock displaced to marginal areas. Fragmentation and habitat loss have been the prevalent drivers of landscape structure. During agriculture expansion between 1880 and 1914, farmland was fragmented by the creation of intricate corridor networks of wirefencerows, railroads, and secondary roads. Increasing rural population promoted tree plantation
around
domestic areas and
along
fences and
roads. Wire-fencerows
deteriorated later when fields were totally devoted to grow crops. Further agriculture intensification, which was accelerated when GM-soybean was introduced, promoted the removal of fencerow to enlarge fields, and the cultivation of road verges. Thus, after nearly 150 years of continuous agriculture, Rolling Pampa landscapes first became much more heterogeneous than the extensive pristine grassland due to agriculture expansion, to be homogenised afterwards by subsequent agriculture intensification. An extensive cropland dominates the Rolling Pampa landscape at present, while scattered woodlots fragment previously open horizons. Wheat predominates during cool-seasons. Soybean, introduced during the 70’s, prevails in warm-seasons, and has significantly reduced the maize area over the last decade.
Ecological processes have been affected by the changes in groundcover and landscape structure induced by agriculture expansion and intensification. Carbon and soil nutrient fluxes were successively altered by numerous factors. Grazing and fire produced early carbon losses and modifications in nutrient cycles in colonial times. During agriculture expansion, grassland ploughing to sown annual crops modified not only chemical and biological soil processes, but also the seasonal dynamics of plant cover, thus affecting the
12 annual patterns of solar energy interception. Soil fertility decreased by nutrient exportation with crop harvests promoting the need of fertilisation to recover soil fertility. Although Pampean soils are naturally deficient in phosphorus, whose availability has considerably decreased because of agriculture, fertilisation is insufficient to balance the annual extraction in crop products
(Michelena et al. 1989, Trigo and Cap 2006) (Fig. 3).
No-tillage, that has been implemented to prevent soil erosion, changed vertical patterns of carbon storage and soil chemical and biological processes. Biogeochemical cycles and plant cover dynamics were also altered by tree plantation and widespread herbicide application on both fields and non-cropped habitats.
Population dynamics and community structuring of plants and animals were affected by landscape fragmentation and spatiotemporal patterns of agricultural disturbance. Grassland replacement by cropland, on one hand, produced the local extinction of many native plant species, but on the other, increased site availability for alien plant species colonising fields, most of them were weeds contaminating crop seeds imported from Europe. Railroad and fencerow corridors served as habitat and conduit for alien species that invaded disturbed land, and have also sustained remnant patches of native vegetation for decades. Since much of the rural population migrated to cities, farm houses and railroad lines were abandoned and invaded by trees and ruderal species. Recent agriculture intensification has strongly reduced habitats for native flora and fauna, as cropland was increased by removing fencerows to enlarge fields, cultivating road verge, and cutting down woodlots in wastelands. Furthermore, agriculture intensification changes the seasonal dynamics of groundcover and productivity, affecting food and shelter availability for wildlife. This process was accelerated when GM-soybean was introduced in Argentina.
Flora and fauna of the Rolling Pampas have been greatly affected by the landscape transformation induced by human activities, particularly because of the widespread effects of agriculture on habitat loss. Flora of the Pampas comprises around 1000 species
13 of vascular plants including aliens of European origin (Parodi 1926, Cabrera 1968). Alien species richness in the Pampas region increased from 314 to 480 between the 1920’s and the 1980’s (Hauman 1925, Söyrinki 1991). When the first floristic study was carried out in the Rolling Pampa during the 1920’s, most extensive grassland had been replaced by crops (Parodi 1930). Landscape richness of remnant grasslands growing in arable soils was ~220, which has been reduced in cropped fields to 53 species, being 21 natives and 32 aliens (Parodi 1926). Weed flora richness continued to steadily increase in the following decades, mainly due to the addition of alien dicotyledonous species (Ghersa & León 1999). However less than 10 years after GM-soybean sowing started, weed richness of summer crops has significantly decreased at both field and landscape scales (de la Fuente et al. 2006, Poggio 2007). Furthermore, agricultural intensification has also reduced the species richness of non-cropped habitats. Despite their low area proportion in both landscapes and fields, fencerows in the Rolling Pampa sustain the highest plant richness, that decrease as greater landscape proportions are devoted to grow annual crops. Thus, it is worth noting that current lost of wildlife habitats in the Pampas should be regarded as the resultant of the application of a “technological package”, comprised by GM-soybean, no-tillage, and glyphosate, in the particular socio-economic context of Argentina.
Fauna has been much more affected than plants by the habitat loss that resulted from agricultural intensification. At present, large mammals have been locally extinct, for example, carnivores like jaguar (Leo onca palustris) or ungulates as pampas deer (Ozotoceros bezoarticus celer), which survive in small populations in protected areas far from the Pampean farmland (Soriano 1991). Populations of ñandú or American Rhea (Rhea americana) were also reduced because fencing limited its running habits and large body size made it more susceptible to hunting. Conversely, several rodent species remain abundant, which find shelter in non-cropped habitats, such as along fencerows and road verges, and differently respond to agricultural activities
(Cavia et al. 2005, Hodara and
Busch 2006). Armadillo species are also common in wasteland and corridors. Birds are
14 also abundant and include many migrant species from North America. Moreover, Pampean avifauna has been enriched by several bird species from neighbouring regions, as a result of new habitat created by fencing and tree plantation
(Ghersa and León 1999).
Since the exportation of agricultural commodities is the most important foreign income of Argentina, policies are strongly oriented to increase agricultural productivity by promoting crop breeding and the adoption of new technologies. Unlike the EU agrienvironmental schemes, Argentina lacks clear policies and actions aiming to reduce the negative impact of agriculture on both biodiversity and the environment at large as well as to restore rural landscapes. Nevertheless, Argentina has the legal framework to promote those actions. The Argentine National Constitution, in its last reform in 1994, specifically includes aspects about rights and duties of citizens and authorities about the use and conservation of natural resources and biodiversity (Constitución del la Nación Argentina 1994, article 41st). On the same year, Argentina also ratified the Convention on Biological Diversity signed in the Earth Summit of Rio de Janeiro in 1992 by enacting a national law (Law N° 24375/1994). An advisors’ committee about conservation and sustainable use of biodiversity is now functioning, and the National Biodiversity Strategies and Action Plans (NBSAPs) has been created for each main region in the country, which include the Pampas (Coordinación de Conservación de la Biodiversidad in http://www.ambiente.gov.ar/).
Nevertheless,
there
are
neither
regulations
nor
prescriptions to prevent biodiversity loss in Pampean agro-ecosystems comparable to the EU agri-environmental schemes. Most actions are concentrated upon inventory of both native and alien invasive species, and to conserve endangered species in non-agricultural environments
(Di Giacomo and Krapovickas 2005, Delucchi 2006).
Discussion
Though they have different landscape structure, landscape history and are under opposite policy regimes, similar large-scale factors drive biodiversity in the two
15 landscapes. Landscape simplification is the dominant factor; two types of heterogeneity are under threat or lost: a reduction in numerous types of landscape elements (diversity of crops, grassland, hedgerows etc.), and a reduction in the significance of natural variation in soil fertility and water availability due to fertilization, drainage etc. While the heavy use of herbicide is a mark of the Pampean region, over fertilization is a characteristic of Brittany, the two being linked through trade.
In both regions, biodiversity is decreasing, either by loss of species, or by replacement of species by less desirable ones. The notable difference is in agricultural policies, strong in one case, inexistent in the other. The changes promoted by the Common Agricultural Policy in the 1960’s have foster environmental degradation in Brittany, but it is difficult to compare the outcome with what the situation might have been under free trade or any other policy. It is also difficult to know if agri-enviromental policies would have been put in place under a situation without policy related to production. The situation between the two countries is also different in terms of public interest in biodiversity. In Europe, NGOs and the public became aware of environmental issues from agriculture and contributed to shift in policies.
Such awareness is limited in Argentina, since communication is poor or even
absent among the different actors (e.g. governmental agencies, environmentalist NGOs, farmers’ associations, and universities), who may implement effective actions to conciliate biodiversity conservation and sustainable agricultural practices in Pampean agroecosystems. But both countries - and all countries- are confronted with a common constraint: the necessity to improve farm productivity to meet the increase of food demand. This constraint will become heavier in the future decades and analyses of the interactions between agricultural development and biodiversity conservation need to be reinforced.
Research on the relationships between agriculture and biodiversity is an important field aiming at providing rules and tools for different management practices (Aviron et al. in press) or policy options. The fact that conservation biology and agronomy has long been
16 separate field remains a conceptual problem (Banks 2004). In itself, the integration of agriculture and biodiversity versus a segregation of the two realms is also a matter of debate (Fischer et al. 2008). Our position is that integration is a necessity to develop the services from biodiversity to agriculture (Isaacs et al. in press). To improve the consideration of biodiversity in policies we must consider two questions: does the scientific literature provide evidence of the effects of agriculture on the various aspects of biodiversity that matters for the society in terms of conservation or resources, and does it propose means to integrate biodiversity in current farming systems or in the design of novel ones?
The two case studies presented above and numerous papers show the tremendous negative effects of agriculture on biodiversity. However, in almost all cases, only the proximal factors are considered in shaping a response, i.e. the direct practices that change biodiversity, not the ultimate causes as how policy drive farmers ‘behavior, or how farm structure constraints farmers ‘options, or the social consequences of biodiversity management. The integration of biodiversity in farming systems/ landscape design and management is typically presented with an emphasis on landscape design (corridors, habitat protection, buffers etc.). The approaches are norms with no consideration of farm diversity, physical diversity (size, soil etc.) or social diversity (type of farmer, economic size etc.). Evidence based conservation (Pullin et al. 2004) aims at providing scientific evidences to design conservation policies. It generally presents factors that can make the policy effective, but do not always provide the cause to effect relationships between policies, their implementation and the fate of the target populations of plants and animals. This may be is one of the reasons why the results of these policies are not often positive (Kleijn and Sutherland 2003).
Conclusion
17 Despite the research investment in ecology, social, economy and policy sciences to provide evidences on the effects of agriculture on biodiversity, integration are still lacking, which precludes actions that may reverse the current trends. Policy makers must be aware of the difficulties and understand that a careful ex ante examination of the possible outcome of a policy is required. For scientists, the main issue is to decipher the role of the different organization levels of the social hierarchy in the dynamics of biodiversity. Presenting two case studies, our contribution shows that the emphasis on local factors is not sufficient, as the drivers maybe very external. The comparison between Argentina and an EU situation raise the question of the evaluation of a given farmer’s activities on biodiversity. In EU programs, only the land a farmer directly utilizes is subject to biodiversity evaluation, not the land its activities actually affect. The same is true when assessing the social dimension of farming. A framework enabling a change in scale permits another view of the relationships between agriculture and biodiversity. It also emphasizes that interactions between the human and the ecological dimension are not only at field, farm or landscape scales but span all scales up to the global one.
Acknowledgements:
The cooperation between the French and Argentine research groups
is supported by the research cooperation program of ECOS Sud (France) and the Ministry of Science and Technological Innovation of Argentina (project A07B04). The French team benefit from the Zone Atelier programme of the CNRS and a grant from the National Research Agency (projet Biosoc,).
We thank Jørgen Primdahl & Simon Swaffield for the
invitation, for comments and English editing.
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21 Figures
Figure 1A:
Figure 1B Figure 1: schematic representation of changes in a hedgerow network landscape: 1A represents such a landscape in the 1930-1960’s, with a continuous network of hedgerows, hedgerows along the riparian corridor. In 1B, many hedgerows have been removed, the network is no more connected, which may arrest the movement of several species. A row of poplars has been planted along the stream, which do not disconnect the slope from the riparian corridor.
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Figure 2: the increase area of no-till and increase use of glyphosate in Argentina
Figure 3: flows of phosphorus from and to Argentina
