Benthic macroinvertebrates and logging activities

At the beginning of the 21 century, the conservation of biodiversity and the sustainable use of natural resources remains a matter of concern. Within this framework, the aim of this research was to study the effects of logging activities on ecological water quality indicators in a tropical forest. The study was undertaken at both local (species/habitat) and landscape (watershed) scales. The study took place on Borneo Island, in East Kalimantan province (Indonesia), in a state-owned timber concession, on an area of 85 km2. In order to study the impact of logging activities at landscape scale, five satellites images (1991, 1997, 1999, 2000 and 2001) were examined. The ecological water quality was evaluate by a biological and a habitat assessment, which were performed at each stream reach. The biological assessment constituted in collected benthic macroinvertebrates. This protocol was conducted at 23 sampling sites on headwater streams in order to compare the impacts of logging in logged area versus unlogged area. Logged area were grouped by the time interval after logging. We examined several groups: recently logged (during logging and until 6 months after logging), 1 to 3 years after logging and, 4 to 5 years after logging and relogged for a second time. Two field seasons occurred in June-August 2000 and April-May 2001. During this eight months time interval, most of the timber concession was relogged for a second time, as a result of the decentralisation process at government level. The research took four years and the following main results have been obtained. Logging activities at landscape scale were quantified by the total length of logging roads. This underlined the intensification of the logging activities from one satellite image to the other over the time (from 1991 to 2001). Vegetation classification and vegetation index (NDVI) could not be used to assessing the impact of logging activities on forest quality because of the homogeneous forest cover in the study site (no visible patches). Benthic macroinvertebrates and environmental variables were considered an ideal tool to assess the ecological water quality in the study site. Macroinvertebrates richness was high with 115 taxa mainly identified at family and sub-family level (genera for Ephemeroptera), but abundance was low (mean density of 770 individuals per square meter, ranging from 86 to 2130). Multivariate analysis highlighted that the size of the streams and the impact of logging activities played an important role in ordinating the samples. A co-inertia analysis demonstrated that benthic macroinvertebrates and environmental variables were found to be strongly related to each others. The main results indicated that macroinvertebrate density, richness, diversity, composition and functional feeding organisation responded to logging activities. During and six months after logging, macroinvertebrate density was higher and diversity indices were lower compared to the reference samples (unlogged situation). One to three years after logging were found to be the most disturbed situation, indicated, among other things, by an even lower diversity indices. Environmental variables responded to logging activities by: an increase in canopy opening, water temperature, amount in fine sediment and flow velocity and by a decrease in Fine Particulate Organic Matter (FPOM). The stream ecosystems seemed to recover 4 to 5 years after logging in absence of ongoing activities, density and diversity seemed similar but benthic macroinvertebrate composition is different compared to reference unlogged situation. Among the 115 taxa identified during the study, several were indicator taxa, meaning that they characterised the impact of logging activities at a given time. Indicator taxa were grouped in five categories: "open canopy" taxa (Platybaetis, Lepidoptera, Hydropsychinae); "sensitive" taxa (e.g. Caenodes, Limonidae, Potamanthus, Perlidae, Philopotamidae); "pulse" taxa (e.g. Psephenidae, Jubabaetis, Platybaetis, Megaloptera, Glossossomatidae) ; "recovery" taxa (e.g. Labiobaetis, Helicopsychidae, Platystictidae) and "adaptive" taxa (Diplectroninae, Simuliidae, Isca). A Tropical Stream Concept was proposed to take into account the paucity of shredders collected in the headwater catchment streams. The higher decomposition rate and terrestrial shredders provides the Fine Particulate Organic Matter as direct input from the washing out of the catchment during rainy events. In summary, macroinvertebrates can be considered excellent indicators, which were successfully used in this tropical environment for both objectives: they assessed biodiversity as an element of forest sustainability and they assessed disturbances due to logging activities, with the advantage to be indicative of recent and past events. Further research is proposed to test the identified indicator taxa to other regions in Borneo, to valid them and to prepare a simplified key to be used by local institutions as a tool for monitoring ecological water quality.

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

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

Clémence Dirac Ramohavelo

EPFL2009