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

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

Soil-vegetation patterns in secondary slash and burn successions in Central Menabe, Madagascar

Slash and burn agriculture is a traditional and predominant land use practice in Madagascar and its relevance in the context of forest preservation is significant. At the end of a cycle of culture, the fields become mostly weed covered and the soil fertility starts to drop. As a consequence, these fields are abandoned (they are called “monka”) and the farmers, in the best case, re-use old surfaces where the vegetation has recovered to some extent. Nevertheless, some of the farmers continue to extend part of their cultures into the natural forest. In order to decrease deforestation, the paper focuses on the potential for agricultural re-use of monkas. To do so, we present the soil–vegetation pattern along a slash and burn successional gradient from newly cultivated surfaces to surfaces abandoned for 40 years. Vegetation relevés were carried out on 61 plots sampled on yellow and red soils, and soil variables such as loss of ignition, pH, total carbon content and total nitrogen content were measured. Results show that: (1) by the 10th year of abandonment woody species are increasing, and after 21–30 years herbaceous plants become less dominant, (2) the species richness increases with age of abandonment, but flattens out by 40 years, (3) by 20 years of fallow, the loss of ignition, total carbon and total nitrogen show similar values or even higher values than in cultivated surfaces, (4) the yellow soils are related to higher pH more than the red soils and are preferred for cultivation, but the higher pH of yellow soils is not associated with higher species richness. Given these results, we conclude that fields older than 20 years have recovered sufficient fertility to be re-used as agricultural land. This re-use would decrease impacts on natural forests. But beyond the nutrient perspective, critical problems remain, including the growing demand for arable land and the need for cultivation to control invasive weeds