Biodiversity sustains key functions of the agro-ecosystem in support of food production. In Europe, an estimated 50 percent of all bird species (~450 sp.) depend on farmland habitats for breeding and feeding. The mutual dependence between biodiversity and farming requires solutions for a win-win partnership. A team of ecologists, agronomists, economists, and mathematicians recently developed a new framework model that explores management strategies aimed at reconciling farming and biodiversity in Europe.
European farmlands host a unique and rich biodiversity, which contributes to ecosystem processes that are essential to agricultural production. This mutual dependence between agriculture and biodiversity has been neglected in the past and solutions for their reconciliation are urgently needed
We propose a new, normative definition of reconciliation: the maintenance of irreducible basic needs of a socio-ecological system. This definition relying on basic needs involve a limited substitutability between criteria, a diversity of reconciliation solutions across systems, the importance of inter-temporal equities and of uncertainties.
The viability theory is a mathematical tool for the multi-criteria analysis of dynamic systems, which makes it very relevant to tackle reconciliation issues.
The FarmBird project relied on modeling and on the viability theory to identify a set of management solutions for the reconciliation of agricultural production and farmland bird biodiversity across France. These solutions targeted different levels organizations, from the field to the landscape and the national territory.
Biodiversity underpins a number of ecological processes crucial to agricultural production. Agro-landscapes are instrumental for the conservation of biodiversity, including wild and domestic species. A key challenge for European agriculture and conservation policies is to develop land-use strategies that reconcile agricultural production and farmland biodiversity.
In this perspective, a range of agri-environmental policies including the Agri-Environmental Schemes (AES) have been developed and implemented. However, over the past 25 years of implementation, their effectiveness for enhancing biodiversity is debatable. Reasons for this low effectiveness include the insufficient uptake of the most constraining policies and the lack of tailoring to different contexts, stakeholders and issues. Farming involves a range of stakeholders : farmers, of course, but also food manufacturers and retailers, consumers, residents of rural areas, naturalists…. Each has an interest in particular outcomes, and some outcomes that are considered desirable by one stakeholder may be irrelevant or even undesirable to another. The consideration of the multifunctional nature of farming is required to develop a sustainable management of resources and biodiversity, bringing together economic, environmental, and social viewpoints. For this purpose, several scientific disciplines must be combined in broad, collaborative efforts. Moreover, insufficient knowledge about agro-ecological processes as well as biophysical and market uncertainties make the decision-making process increasingly complex. In this context, assessing and comparing different solutions through quantitative methods is useful.
A scientific definition of “reconciliation”
To grasp what is meant by reconciling agriculture and biodiversity, we propose a two-stage definition. First we formulate a normative statement that can be interpreted as an axiom.
We define reconciliation as the maintenance of a hard core of irreducible basic needs of a socio-ecological system (SES), defined as a system of people and nature. We focus here on agro-ecosystems, agro-ecological entities that are functionally and geographically consistent, including interactive living and nonliving, human and non-human components. The basic needs of this SES refer to humanity’s essential needs as well as those of the ecosystem . These needs are not all defined in an absolute way; especially, humanity’s needs emerge from the moral and social goals of a civil society and government. These basic needs may refer to different characteristics of the SES, such as the ecological, economic, or social performance, and may involve different subgroups of the society (farmers, consumers, conservationists, etc.).
We argue that this normative definition of “reconciliation” is sufficient to deduce a set of four properties representing the practical characteristics of reconciliation:
- The irreducibility of basic needs implies a limited substitutability between the different criteria representing these needs. By definition, a decision underlies trade-offs among different criteria; final decision represents a specific combination of these criteria within the set of available combinations. It is possible to switch from one combination to another by substituting one criterion for another. For example, some people accept that they must increase their working hours to earn more money. However, this substitutability is not infinite because of the basic needs of sleeping or eating. In this example, basic needs define the limit of substitutability. By extension, for the reconciliation of agriculture and biodiversity, the limits of substitutability come not only from social choices (avoiding shrinking economic growth, a less meat-oriented diet, saving specific species from becoming extinct, etc.) but from climatic, ecological and bio-physical needs. The key ecosystem services, such as soil structure and fertility, pollination, are good examples of these needs. Along with production factors, these needs influence the capacity of the land for food production and other ecosystem services at sustainable levels.
- The choice of SES as unit of work plaids in favor of a portfolio of solutions to reconcile agriculture and biodiversity at large scale. Indeed the diversity of needs across societies and agro-ecological conditions leads to a variety of SESs in both composition and structure. For example, moral statements about genetically modified organisms differ in Europe and the USA; insects are eaten in 29 and 36 countries in Asia and Africa, respectively, but do not represent an edible protein source in Europe. Similarly, climatic and biophysical needs vary within different geographical regions. Due to the diversity of SESs, different agricultural management options coexist today, ranging from low-input wildlife farming to industrial agriculture. This range of options deserves evaluation and should be combined in a portfolio of solutions to reconcile agriculture and biodiversity.
- Basic needs are related to society as a whole. Society shall not be seen in a static way. In this sense, irreducible basic needs have to be defined for both present and future generations, which implies taking careful consideration of the temporal aspect. The balance between different criteria among actors from the same generation has to extend to the other generations. The balance between intra- and inter-temporal equities should be assessed according to social preferences and taken into account.
- The integration of non-human components, both living and non-living, implies uncertainties (such as climatic and market uncertainties). Their combined effects make the context of farming structurally uncertain. In this context, the fulfillment of basic needs is more successful by handling the uncertainties rather than ignoring them. Dealing with the unpredictable events requires a paradigm shift from controlling the environment to working with environmental uncertainty. This implies assessing properties such as resilience, robustness or adaptability of SES.
How viability theory helps the reconciliation of agriculture and biodiversity
The viability theory was developed by the French mathematician Jean Pierre Aubin. Its main principle is to define objectives as red lines not to be crossed instead of criteria to be maximized. A two minutes video on viability theory is available on Youtube.
Mathematically, viability denotes the simultaneous respect of a set of constraints. These constraints represent limits within which a dynamic system should be maintained throughout time. In our case, one limit can represent for example a minimum threshold of production performance, a second one can correspond to a social threshold, and a third can stand for an ecological threshold. These limits are defined according to the basic needs of the SES. The viability approach aims to identify the set of solutions (e.g., in terms of land-use management or public policies) to ensure that the whole set of basic needs is met. By maintaining the SES within these limits, these solutions enable its sustainability. They are thus denoted ‘viable’ and form the viability kernel (see box).
We argue that the viability framework offers a new theoretical prism to explore the reconciliation of agriculture and biodiversity. There are four related arguments, highlighting the relevance of this theory for sustainable management:
- By identifying solutions that satisfy a set of constraints, viability theory is consistent with the multiple criteria approach to reconciliation. Accounting for each criterion separately instead of adding them to form a single criterion limits the substitutability among criteria and ensures the satisfaction of safe minimum standards for each criterion. Moreover, viability theory makes it possible to assess each criterion within its measurement unit, avoiding the technical and philosophical problems of aggregating criteria into a single unit (often a monetary unit).
- By promoting a set of viable solutions instead of one unique optimal solution, viability theory is able to account for the spatial heterogeneity of the SES. A portfolio of viable options can be revealed to deal with local specifics, which takes advantage of environmental variability. The viability theory thus offers management flexibility at national scale that is required to reconcile agriculture and biodiversity over the range of the local SES.
- By accounting for a temporal context, viability theory ensures that constraints are respected over time. The combination of short- and long-term constraints according to social preferences helps formalize temporal trade-offs. Beside constraints related to short term sustainability, it is possible to formalize constraints at time horizon that will reflect the state in which the system shall be left to future generations. The viability theory identifies present solutions that avoid future crises without penalizing the present generation. Taking into account dynamics makes the viability theory explicitly able to address transitory states, which could be crucial to manage non-equilibrium SES.
- By taking into account uncertainties, these viable solutions can be interpreted in relation to the resilience of the SES. The viability theory is particularly suitable to assess the resilience of a system that has no equilibrium state or in which the state of equilibrium is not the desired state (e.g. extinct populations). By explicitly accounting for management actions in an adaptive framework, the viability theory makes it possible to measure the adaptability, flexibility and robustness of a system to different types of perturbations. Assessing the adaptability of the system makes it possible to face a strong variability and leads to the design of resilient systems.
Options for reconciliation
A recent project called FarmBird, designed by three major French research institutes, aims to identify a generic set of sustainable management strategies for major agro-ecosystems across France. A process-based modeling approach uses viability theory to assess reconciliation in agro-ecosystems, where food production conflicts with bird conservation. One novelty of this modeling approach is to explore options at different levels of organization (field, farm, landscape, small region, and national territory). It combined five different components: policy decision makers, farmers, land uses, habitat quality, and bird biodiversity. There is an explicit distinction between decisions made by individual farmers and those made at the policy level. Policies are implemented at national level by allocating subsidies relative to the given budget and social preferences. Management decisions by farmers are local and affected by national policy. Land-use patterns arising from such decisions have a direct impact on food production and both direct and indirect impacts on biodiversity. The outcomes of agro-ecosystems are thus split into a private component (food production performance) and a public component (ecological performance). Ecological performance emerges through the links between land use, habitat quality, and species’ traits . Finally, the economic, production, and ecological outcomes are assessed and subsequently influence the policy component.
Planning the spatial allocation of land use improve biodiversity without impairing production
The trade-off between agricultural production and biodiversity conservation is influenced by land use, including its diversity and spatial configuration1. Several studies highlight landscape heterogeneity as a factor promoting the diversity of available habitats, thus allowing higher levels of biodiversity2. At larger scale, land use and intensity allocation strategies have been emphasized as solutions for reconciling production and biodiversity3.
The FarmBird project took a step further by demonstrating that the spatial allocation of land use and intensity shifts the boundary of the trade-off between production and biodiversity. At the landscape scale, the simulation of a large number of land use configurations reveals that for a given level of agricultural production, bird population sizes can be improved by changing the spatial arrangement of mowed and grazed fields4. On a larger spatial scale, over the entire French territory, we also demonstrated that land-use intensity and its spatial allocation are two complementary options to shift the trade-off boundary. Notably, some specific allocations lead to improvements in biodiversity without losing either the quantity or value of agricultural production5. The benefits of land use heterogeneity emerge from the existence of interacting suboptimal habitats, where each type of land use provides some of the necessary resources, and species mobility among land-use types enables bird populations to obtain all needed resources.
At both the landscape and national scale, solutions relying on the spatial allocation of land uses and intensities require spatially targeted changes. For example at national scale, many small decreases in extensive areas can reinforce spatially the extent of “High Nature Value” areas and provide a high net benefit in terms of biodiversity6. At the landscape scale, small land use changes in the right areas can improve heterogeneity and provide bird access to complementary resources within their mobility range. Such solutions are interesting to explore with policymakers in terms of the consequences of new policies, helping them to identify and assess regions of higher and lower grazing intensities. They can lead to higher awareness among policy makers and farmers regarding the scope of biodiversity-friendly land use strategies and the need for spatially coordinated and targeted decisions to attain them.
Farming and biodiversity can coexist if a fine tuning of land use management is implemented
A long history of research on the impact of grazing management on farmland biodiversity reveals the production/biodiversity trade-off. These studies generally conclude that both intensive and no-grazing areas are detrimental to the grassland bird life cycle, in contrast with light-to-moderate grazing7. Many authors have suggested that decreasing livestock density is a key management tool to conserve grassland birds. However, these arguments lack quantitative assessments and implicitly suggest that improving the biodiversity performance of a productive grassland system simply involves the introduction of light-to-moderate grazing.
Using a viability model accounting for both direct and indirect effects of grazing on population dynamics of the Northern Lapwing and Common Redshank, we showed that for a given level of production, different management timeframes can lead to different ecological performance8. The management practices that are the most suitable for these two bird species are characterized by a fine adjustment of the timing of grazing (i.e., temporal heterogeneity of grazing). At the farm level, this model also shows that the proportion of land uses with different intensities determines the trade-off between production and bird population size9.
We suggest that adjusting grazing intensity is an efficient solution to streamline the temporal variations in both grazing period and intensity. We provide a quantitative tool for a two-fold assessment of negative impacts of either the absence of grazing or the inappropriate temporal distribution of grazing intensity. This solution helps to explore how grazing can be used as a tool for managing habitat quality to beneﬁt both bird populations and livestock. All viable grazing strategies include spring grazing, which is an interesting result given that the exclusion of livestock during spring has been advocated as a desirable way to manage grasslands for the beneﬁt of grassland birds in Europe10, despite of the importance of spring grazing for production.
Adopting result-oriented agri-environmental schemes (AES) allows more management flexibility
Result-oriented AES have been proposed to improve the efficiency of biodiversity and ecosystem service policies11. Unlike action oriented AES, they rely on payment for effective biodiversity conservation that is independent of the management practices implemented by farmers. Result-oriented schemes are expected to allow farmers to develop innovative management practices that would make both productive and ecological performance more efficient. However, the relative performance of action-oriented vs. result-oriented AES is unknown; whether result-oriented AES are likely to improve ecological or productive performance without decreasing performance in other dimensions is still being discussed.
Using the viability model, we revealed that result-oriented AES lead to much a better ecological performance than do action-oriented AES, whereas productive performance remains quite similar in both types of AES12. The authors show that result-oriented AES enable a higher management flexibility. This difference in flexibility is even greater when the grassland agro-ecosystem is exposed to climatic uncertainty12.
Current action-based AESs result in poor effects on biodiversity13,14 and are often subjected to the opportunistic behaviors of farmers. Result-oriented AESs can lead to greater commitment of farmers to conservation issues if these issues are perceived as opportunities rather than constraints, enabling payment of farmers for the production of biodiversity and promoting situations in which farmers are not told how to modify their management practices but are left free to experiment, choose, and adapt practices that favor biodiversity in their local context. This approach results in greater management flexibility and improves the ability of farmers to adapt to environmental variations.
Apparently contradictory objectives can be reconciled with relevant public policies
Most studies based on optimal control approaches revealed a Pareto optimality between the ecological and economic performance of agriculture15. In other words, there was no unique win-win public policy in which economic and ecological performance would be simultaneously maximized. Other studies have shown that different biodiversity objectives can be antagonistic, such as between the mean trophic level and the degree of specialization of farmland bird communities16.
We showed that viable policies combining different policy instruments are able to promote economic performance on farms while conserving farmland bird populations17. Such viable policies make apparently antagonistic objectives compatible, since income-based indicators, budgetary indicators, the Farmland Bird Index, the mean trophic level, and the mean specialization degree of farmland bird communities are simultaneously satisfied. Viable policies tie reduced subsidies or even taxes on crops and increased subsidies on extensive grasslands. While most of the focus has been today on local and specific measures, our results highlight the importance of using simultaneously all the kinds of policy tools available in the CAP in the reversal of biodiversity declines.
From a policy perspective, our study suggests that the current CAP is one of the key drivers that negatively impacts agricultural sustainability, as it is not able to efficiently manage a satisfactory balance between externalities. On one hand, negative externalities, such as those emerging from intensive crops, should be penalized, or at least not be encouraged. On the other hand, positive externalities from grasslands should be both supported and subsidized. However, this solution raises questions in terms of social acceptability. Subsidies do not generally raise substantial concerns in terms of acceptability among farmers, as they constitute a financial gain. By suggesting the maintenance and reinforcement of direct subsidies for extensive grasslands, which have been implemented since 2005, our results are in line with current public policies. In contrast, there are questions about the acceptability of decreasing crop subsidies, particularly among arable farmers. The analysis of all viable strategies offers fruitful information in terms of acceptability and governance. Budgetary issues are not the most stringent constraints of all viable strategies, as some strategies have solvent budgets18. A monetary redistribution could thus be considered for farmers incurring private costs and losses due to crop subsidy reductions. Such a financial reallocation could be an interesting option to promote the acceptability and governance of such strategies.
Reconciling agricultural production with biodiversity conservation will lead to mutual benefits and to improve the sustainability of farming. We provide an innovative definition of reconciliation which focuses on the maintenance of essential needs of humanity and ecosystems. This definition tackles key issues related to sustainability: its multi-criteria nature and the limited substitutability between criteria, the diversity of goals and solutions across systems, and the importance of the time dimensions for harnessing uncertainty and equity. Within the frameworks of this definition, the FarmBird project adopted a modeling approach to identify several solutions for reconciliation. The theory of viability – which seeks solutions satisfying a set of multi-criteria constraints over time – provided a uniquely adapted mathematical framework to explore reconciliation. Solutions for the reconciliation of farming and biodiversity are identified at different scales: field, farm, landscape, region and country. These solution include optimal land use allocations, temporal management and flexibility of grazing, result oriented measure and redistribution of the subsidies. The extensive agri-environmental policy mechanisms in the European Union provide a strong potential for the implementation of these solutions; however, limitations of the current policy tools also challenge this implementation. Several tools already exist but should be disseminated (e.g. result oriented measures) or developed for other scales, which could be challenging. For instance, applying spatially targeted measure to reach optimal land use allocations at the landscape or country scale would require coordination between different stakeholders. Other tools would involve radical changes of the current CAP (e.g. redistribution of the subsidies) and could raise challenges for social acceptability.
This work was carried out with the financial support of both the ANR – Agence Nationale de la Recherche – under the “Systerra program – Ecosystems and Sustainable Development”, project “ANR-08-STRA-007, FARMBIRD”.
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