A game-theoretical model of deforestation in human-environment relationships

We studied a two-person game regarding deforestation in human–environment relationships. Each landowner manages a single land parcel where the state of land-use is forested, agricultural, or abandoned. The landowner has two strategies available: forest conservation and deforestation. The choice of deforestation provides a high return to the landowner, but it degrades the forest ecosystem services produced on a neighboring land parcel managed by a different landowner. Given spatial interactions between the two landowners, each landowner decides which strategy to choose by comparing the expected discounted utility of each strategy. Expected discounted utility is determined by taking into account the current and future utilities to be received, according to the state transition on the two land parcels. The state transition is described by a Markov chain that incorporates a landowner's choice about whether to deforest and the dynamics of agricultural abandonment and forest regeneration. By considering a stationary distribution of the Markov chain for land-use transitions, we derive explicit conditions for Nash equilibrium. We found that a slow regeneration of forests favors mutual cooperation (forest conservation). As the forest regenerates faster, mutual cooperation transforms to double Nash equilibria (mutual cooperation and mutual defection), and finally mutual defection (deforestation) leads to a unique Nash equilibrium. Two different types of social dilemma emerge in our deforestation game. The stag-hunt dilemma is most likely to occur under an unsustainable resource supply, where forest regenerates extremely slowly but agricultural abandonment happens quite rapidly. In contrast, the prisoner's dilemma is likely under a persistent or circulating supply of resources, where forest regenerates rapidly and agricultural abandonment occurs slowly or rapidly. These results show how humans and the environment mutually shape the dilemma structure in forest management, implying that solutions to dilemmas depend on environmental properties.

Dead wood in managed forests: how much and how much is enough?

Rita Bütler Sauvain

The aims of this research were twofold: to develop an efficient method for the quantification of large spruce snags (standing dying and dead trees), and to establish snag target values for sustainable forest management. We answer the two basic questions: how much dead wood is currently available in managed forests? And how much dead wood is enough for biodiversity conservation? It is widely accepted that modern forest management has to be sustainable. One generally recognised criterion of sustainability is the maintenance of biodiversity. Since this concept encompasses a large range of scales and features (landscapes, ecosystems, species and genes; components, processes, functions, etc.), biodiversity indicators have been identified for measurement and monitoring purposes. "Dead wood" has been recognised as a key indicator for biodiversity in forest ecosystems. Verifying and assessing progress towards biodiversity maintenance or restoration hence requires the measurement of different kinds of dead wood. Yet cost-efficient and rapid methods are still lacking. That is why we developed in this thesis an efficient method for the quantification of large spruce snags. Being based on infrared Aerial Photos and a Geographic Information System (GIS), it is called the AP-GIS-method. It enables mapping of snags and calculation of the spatial snag-density, i.e. the number of snags per hectare, and can be used to answer the question: How much dead wood is in managed forests? Beside techniques to assess dead-wood quantities, forest managers need quantitative target values, i.e. guidelines in order to know how much dead wood should be maintained in managed forests for biodiversity conservation. Natural forests may be used as reference systems to define such targets. However, since dead-wood amounts in natural forests may be extremely high, up to 30% of dead trunks, the retention of such amounts in managed forests would hardly be compatible with economic objectives. Another possibility for defining guidelines is the translation of the habitat requirements of deadwood- dependent species into management targets. The Three-toed woodpecker Picoides tridactylus has previously been recognised as a potential indicator species of features characteristic for forests with natural dynamics (especially old-growth). Although ecological studies had demonstrated its need of dying and dead trees for foraging, nesting and drumming, the required density of such trees has never been quantified. In this thesis, we analysed the dependence on dead wood for both European subspecies, the Alpine Picoides tridactylus alpinus and the northern P. tr. tridactylus. The study was conducted in sub-Alpine spruce forests in Switzerland and boreal forests in central Sweden. In both countries, we found a significant non-linear response of the probability of woodpecker presence to different amounts of dead trees, and identified critical ecological thresholds for the local presence of this species. Clearly, the Three-toed woodpecker depends on relatively high amounts of dying and dead trees. In Switzerland, the road network density negatively affected the presence of this woodpecker species, since a high road density facilitates forest management intensification and the removal of diseased and dead trees. Based on our results, and since several other links with biodiversity have previously been demonstrated, we suggest that Three-toed woodpeckers be considered indicators of dead wood and habitat quality. This species has therefore been used in this thesis to find an answer to the question: How much dead wood is enough in managed forests? In order to ascertain dead-tree targets, we developed a bioenergetic model for Threetoed woodpeckers, enabling estimation of snag amounts required by this species to satisfy its energy needs. By comparing modelling results with the previously identified critical dead-wood thresholds, we were able to derive reliable targets, since both approaches resulted in similar critical values. We recommend, for both boreal and sub-Alpine spruce forests, aiming for 5% of the standing tree basal area, or volume to be dead. Such snag-retention levels, to be applied over an area of about 100 ha, correspond in sub-Alpine forests to a basal area of ≥ 1.6 m2 ha-1, or a volume of ≥ 18 m3 ha-1, or a minimum of 14 snags with a diameter ≥ 21 cm per hectare. Considered as a pragmatic way to stimulate forest managers' interest in dead wood maintenance or restoration, we analysed the potential usefulness of Three-toed woodpeckers as natural agents against bark beetles. By defining three scenarios for different levels of woodpecker effectiveness, we compared the numbers of bark beetles consumed with those caught in pheromone traps used in forestry. We demonstrate that woodpeckers catch 2-19 times more bark beetles than traps do. This result is true for both cases, when one woodpecker is compared with one trap, and when the whole Swiss woodpecker population is compared to all traps installed in Swiss forests.

EPFL2003

Land use changes and transnational migration

Silvia Hostettler

The present study focuses on the economic, political/institutional, technological, cultural, demographic and environmental drivers of land use change. It aims to understand the factors influencing land use decisions at the household level, in particular the influence of migration. The study is guided by the hypothesis that international migration is driving land use change through the investment of remittances, funds sent back by migrants to their families in the country of origin. This research is based on a political ecology approach and the conceptual framework relies on three theoretical concepts. First, the concepts of proximate causes and driving forces were used to identify the factors behind changing land use. In addition, the concept of remittance landscapes, a concept developed in the framework of this study, which is defined as an emerging type of landscape driven by the investment of remittances, was used to evaluate the impact of remittances on land use in the study area. Fieldwork was conducted in the municipality of Autlán in the state of Jalisco in Mexico over a total period of 8 months between 2002 and 2004. Land use changes between 1990 and 2000 were quantified based on satellite image analysis. Underlying driving forces of these changes were examined based on land use change data collected by survey as well as data available from municipal, state and federal agencies. Land use changes observed in the study area between 1990 and 2000 include a slight increase of agricultural land (2%), of urban land cover (0.5%) and of pine-oak forest (0.7%). Over the same period, pasture increased by 18% while dry forest decreased by 10%. Rapid and extensive land use change is occurring on rainfed agricultural land, as maize cultivation is converted to the cultivation of agave azul used for the production of tequila. The first plantations of agave azul were established in 1996 and by 2002, agave azul was planted on 33% of all rainfed agricultural land of the municipality. 84% of owners of rainfed land included in the survey had changed land use from maize to agave during this time period. The dynamics of several proximate causes are driving this change: 1) Market prices for maize decreased by 46% between 1994 and 2004 while the costs for agricultural inputs continually increased so that the cultivation of rainfed maize was no longer economically profitable; 2) The variability of rainfall combined with a lack of irrigation water limits the choice of economically viable alternatives to agave azul; 3) In the large majority of cases, landowners rent out their land to tequila companies in reverse leasing arrangements for seven-year periods (the duration of one growing cycle of agave azul). During this time they do not have to work on their own fields and are free to find off-farm employment or to migrate to the US and; 4) Landowners continue to receive agricultural subsidies even though the land is rented out, as agave azul is one of the eligible crops. Overall, the main driving forces identified in the study area are economic (market prices), environmental (variability of rainfall, soil quality, topography), political/institutional (agricultural subsidies, land tenure) and demographic (labor availability). Technology and culture appear to be less important. Results of the present study confirm the hypothesis that global factors, especially international trade agreements such as NAFTA (North American Free Trade Agreement) increasingly influence land use change. However, they are not sufficient to function as a sole driver of land use change. Environmental factors are a critical determinant of whether a certain land use change will occur or not. The decisive aspect behind the observed land use changes are the multiple interactions between specific factors at different levels and not the predominance of one particular driving force functioning at a particular level. International migration is a significant livelihood strategy in the study area, especially for lower-income communities. On average, 50% of all households have or had at least one family member in the US as a migrant between 1980 and 2004, and remittances represent 45% of total household income. In general, the bulk of remittances income is used for subsistence needs and to repay debts. Nevertheless, on average, 30% of migrant households invest remittances in land, livestock, agricultural production and in house construction. All these investments lead to land use changes. The impact of remittances on land use changes is variable, and depends on the socio-economic, political and environmental context of the community and the individual situation of the migrant household. In low-income communities, remittances might be used to repair existing housing, while in higher-income communities, remittances are used to construct a new house, converting agricultural to urban land. With regard to changes in labor availability due to out-migration, the results are ambiguous. Migration can drive land use change by encouraging a shift to low-labor land use systems, but these land use changes that require less labor can also drive migration. The concept of remittance landscape developed by the researcher has proved useful for analysing the impact of remittances on land use changes. A combination of area-based and actor-based evaluation criteria are effective in order to describe quantitative as well as qualitative landscape transformations driven by the investment of remittances. Landscapes where the investment of remittances leads to a change of land use from subsistence to cash crop cultivation should be included as a potential type of remittance landscape, even though the basic type of the landscape (agricultural) remains unchanged. Accordingly, at least six different types of transformations into remittance landscapes are possible: a) forest to pasture, b) forest to agriculture, c) forest to urban, d) agriculture to pasture, e) agriculture to urban and f) change of agricultural system. In conclusion, the study area on which this research focused is not considered to contain any remittance landscapes because remittances are only partially driving the extensive land use changes occuring in the region.

EPFL2007

Stratégies villageoises pour la gestion des paysages forestiers du Menabe Central, Madagascar

Clémence Dirac Ramohavelo

Introduction In order to reduce deforestation, the current attitude of conservation programmes and forest politics does no longer ban the local populations from the forests, because such measures present negative consequences for the communities. Today's tendency is to focus on a multifunctional planning of the forest landscape that combines the conservation of biodiversity with the long-run improvement of local livelihood. Following this global trend, Madagascar – biodiversity hotspot of international importance – has been passing through a process of devolution of the renewable resources management rights to local communities since 1995. Because of a too strong human pressure, the Malagasy forests have been drastically reducing; the conversion of forest soils into cultivated lands is the major cause of deforestation. In Madagascar, cultivation is the main activity in rural areas, and 73.5% of rural population is still living below the poverty line. Research background In the Central Menabe region, west coast of Madagascar, the annual loss of forest cover (dry dense forest) is about 1%. Numerous researches were carried out on the forests or on the man-forest interface in Central Menabe, but studies focusing on interdisciplinary questions at a regional level are rare. A forest landscape research that considers villages, cultivated fields, secondary vegetations and natural forests is therefore necessary to propose regional forest landscape management recommendations. Such a research project aiming at providing scientific information for a sustainable, multifunctional and participative forest landscape management was launched in 2005 in this region; the present PhD thesis integrates with this research project. Objectives, methods and results The PhD thesis aims at setting up a scientific basis for a sustainable management of forest soils, non timber forest products (NTFPs) and forest services. This management tries to answer, in a participative way, the local populations' needs and expectations while decreasing the pressure on biodiversity. The research methodology comes from social (questionnaires, surveys, participant's observations, scoring exercises) and natural sciences (inventories and descriptions of the cleared surfaces, NTFPs' inventories). The analyses were done mainly by means of non parametrical tests, and calculations of averages, standard deviations and frequencies. The following paragraphs present the PhD thesis's specific objectives and the obtained results. To analyze the socio-economic role and ecological impact of cultivation in the Central Menabe rural system Rice and slash and burn cultivation products are the objects of a bit less than the half of rural commercial transactions. Rice is the product the most marketed, but its supply is judged insufficient. The slash and burn cultivation contributes intensively to the rural households' alimentary and financial safety, but the commercial interest in its products remains weak. The surfaces of the clearings for cultivation vary between 0 and 2 ha, but it is difficult to estimate the frequency of the different types of vegetation that are cleared. Nevertheless, clearings for rice cultivation (cultivation principally done on irrigated plots) are less frequent than the ones for slash and burn cultivation. To analyze the socio-economic role and potentialities of the small and big livestock, and to assess the environmental impact of the big livestock Dependently on the breeders' ethnicity, zebus represent a social (enhancing of the breeder's social prestige) or an economical (products' utilisation or sale) value, always slightly lucrative. The small livestock's products contribute more intensively to the households' budgets, because the majority of the breeders sell these products for emergency or precise needs. The use of fire to renew pasture lands accentuates the deforestation, and the overgrazing present during the dry season creates local ecological instabilities. To analyze the NTFPs' socio-economic potentialities and to assess the harvests' environmental impact Amongst the four studied NTFPs, tenrec (Tenrec ecaudatus) is the one economically the most promising. For tenrec as for both tubers, traditional harvests do not represent a threat for the upholding of the species; however, the destructive harvest of wild honey perils the long-run survival of the bees' specie. To analyze the possibilities and political choices concerning the biodiversity conservation payments PES (payments for environmental services) programmes proposing payments in kind would be suitable, on some conditions, to protect biodiversity and to reduce poverty in Central Menabe. These conditions are i) to establish a PES contract with villages that are aware of biodiversity conservation and other economical potentialities, and ii) to focus the PES's goal on deforestation decrease and not on its full cessation. To synthesise, on a regional level, the socio-economic role and ecological impact of the main villager land uses, and to analyze the potentialities and the constraints of an optimisation of the forest landscape traditional use Socio-economically, cultivation and small livestock represent the main activities that insure the rural households' alimentary and financial safety. Ecologically, clearings for cultivation and big livestock's pastures are the activities generating the most destructive environmental impacts. Globally, the optimisation of cultivation techniques, the chicken breeding development and the improvement of the pasture management present big potentials to optimise the rural livelihood while decreasing the pressure on biodiversity. More detailed recommendations are presented in the chapter 7. Global synthesis and conclusion The recommendations are divided into three categories: some only act on biodiversity conservation, others have an exclusive effect on livelihood improvement, and some contribute to the both goals. This highlights the necessity to consider both the relation between biodiversity conservation and livelihood improvement, and other alternatives that are particular either to biodiversity conservation or to livelihood improvement.

EPFL2009