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alt=|vignette|344x344px|Forêt tropicale d'Amérique du Sud vignette|upright=1.3|Vue intérieure d'une forêt tempérée mixte en France. vignette|upright=1.3|Bush australien. vignette|upright=1.3|Forêt inondée en Pologne. vignette|upright=1.3|Forêt tempérée de résineuxîles San Juan, État de Washington. Une forêt ou un massif forestier est un écosystème, relativement étendu, constitué principalement d'un d'arbres, arbustes et arbrisseaux (fruticée), ainsi que de l'ensemble des autres espèces qui lui sont associées et qui vivent en interaction au sein de ce milieu. Elle peut être naturelle ou exploitée en sylviculture. Les espèces animales, végétales ainsi que les champignons qui vivent au sein des forêts sont qualifiées d'espèces forestières. Un boisement de faible étendue est dit bois, boqueteau ou bosquet selon son importance. Divers types de forêts existent ; des forêts primaires aux forêts dites urbaines, avec les gradients intermédiaires. Elles peuvent être naturelles ou exp

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

Improving slash-and-burn agriculture in Central Menabe, Madagascar

Justine Marie Gay des Combes

Slash-and-burn agriculture is considered as an important driver of deforestation in the tropics. In Madagascar, a biodiversity hotspot, this type of agriculture particularly threatens the tropical forest cover. On the south-western coast of the island, in Central Menabe, the dry tropical forest of Kirindy suffers from an annual deforestation of 2.6%. At such alarming rate, the forest will have entirely disappeared by 2050. The attention of past research programs and conservation actions were mainly on studying the forest or the general interactions between local populations and the forest, with little focus on the slash-and-burn agricultural system itself. Hence, understanding the cultivation practices and assessing alternatives to them is crucial to improve the current forest conservation initiatives. The present thesis answers to the need of an in-depth study of the agricultural practices in Central Menabe. The project aims to (1) analyze the practices of slash-and-burn cultivation in Kirindy forest, (2) explore alternative slash-and-burn practices which may be more sustainable for the forest, (3) determine the implementation perspectives of these alternatives. In a first stage, we have characterized soil productivity along repetitive slash-and-burn cultivation cycles and the farmerâs perception of their agricultural system. Then, we experimented a selective slash-and-burn agriculture (where trees are left intentionally within the cultivated fields), coupled with compost amendment. Finally, we have assessed the implementation potential of that technique through interviews and participating workshops with local farmers. Our findings highlighted that soil depletion due to plant uptake and erosion or leaching by heavy rains, as well as weed invasion were important problems of slash-and-burn cultivation in Central Menabe. Farmers perceive weeding as a work overload. Decrease in grain yield due to slash-and-burn agriculture reaches about 40% after three years of cultivation on the same field (from 4 to 2.5 t ha-1), and decreases up to 75% after a single cyclonic rainy season (from 4 to 1 t ha-1). Further, we demonstrated that combining compost and wood ashes (from the burnings) seems a promising solution to sustain cultivation on the fields. Compost, combined with wood ashes, multiplied corn yield by 5 compared to traditional slash-and-burn agriculture. Growth rates were accelerated and phenology stages of maize plants advanced. Furthermore, this combination also increased soil security by improving the remaining stock of nutrients after a rain simulation. On the other hand, a partial remaining tree cover (selective slash-and-burn agriculture) improved corn yields only when the soil was amended with ashes, not with compost, nor the combination of both. Implementing composting in the forest dwelling communities appears to be a challenging task. Several barriers were highlighted, among them the most important was the water constraints during a consequent period of time related to compost maintenance. Alternative slash-and-burn practices have not been much studied so far because the use of fire was always considered as destructive. Thus, our result will contribute to the development of new forest management strategies which would balance conservation of habitats and rural communities agricultural needs, while minimizing the impact on primary forest.

EPFL2017

Prevention of forest fires in a changing climatic context in Ticino, southern Switzerland

Michael Reinhard

Switzerland is not a place commonly associated with forest fires, unlike many areas of the nearby Mediterranean Basin. However, in this Alpine country, forest fires occur every year and destroy forests that fulfil various functions, the most socially and economically important of which is protection from natural hazards. Canton Ticino is the most affected by forest fires. The protective function is of vital importance for local communities. Most of Ticino's population lives in valley bottoms, where most transportation infrastructures are built, and without forests these are vulnerable to mass flows. In Ticino, forest fires occur mostly during the winter/spring season when dry conditions occur due to low precipitation and strong Foehn events. At this time, deciduous trees have shed their leaves and there is an important seasonal accumulation of dry litter on the forest floor. Fuel load has also increased over recent decades due to the abandonment, since about 1960, of traditional agro-forestry activities that removed dead wood, dry leaves and forage grass from the forest. Fuel in the forest is particularly flammable during the dry winter and leads to very high fire risks. Climate change has contributed to increasingly fire-prone conditions over the past decades and may also have had an effect on forest composition. Most Ticinese forest fires are anthropogenically triggered and negligence is the primary cause of fires. The only natural cause of fire is lightning, which affects forests particularly during summer, when heavy storms occur. This dissertation aimed at gaining a better scientific understanding of the interactions between landscapes, humans and forest fires in the context of climate change, in order to prescribe recommendations to achieve forest fire prevention and diminish fire related risks. We focused on the mechanisms leading to forest fires and adopted an integrated approach, which necessitated the use of a variety of methods: i) climate trend analyses, ii) flammability tests using a standardised ignition apparatus and a thermo-gravimetric analyser, iii) qualitative social science methods using focus groups and semi-structured interview techniques, iv) quantitative social science methods by means of a questionnaire. The results suggest that climate has changed in recent decades with more frequent and intense fire-prone conditions. Minimum and maximum temperatures have both increased significantly and relative humidity has decreased significantly for all daily measures during fire season. The present study suggests that fire-prone conditions are likely to become even more acute. Climate also has an important impact on the composition of the forests and the state of vegetation, as well as the condition of the fuel load. The most flammable species (Castanea sativa and some laurophyllous species) tend to occur near human settlements and this is of importance for management. Some of these species are expected to increase due to climate change. People involved with the forest fire prevention system perceived the actual fire policy as generally well working and well planned, and they perceive preparedness as strong, although discussions showed that the prevention of accidental fires is not addressed by the current fire policy. Effective prevention requires accurate information about the social aspects of forest fires, which until now has not been available in Ticino. Mechanisms leading to fires are not very well understood by locals, although many people identify correctly some technical aspects of forest fires. Depth of understanding is related to geography, gender, age, profession, marital status, income and life-style. Differences between these socio-demographic groups and geographical patterns suggest that prevention needs to be better targeted and that the population cannot be treated as a homogeneous entity. We conclude the dissertation with a series of recommendations for local authorities and people involved in the forest fire policy setting. These recommendations concern climate, vegetation flammability and forest fire prevention in Ticino.

EPFL2006