5. Ferramentas e métodos para conservação e o manejo – Temas
Benoit de Thoisy Cecile Richard-Hansen, Philippe Cerdan, Regis Vigouroux, Bertrand Goguillon
HUMAN FOOTPRINT IN FRENCH GUIANA: A RELIABLE SURROGATE TO THREATS ON BIODIVERSITY ?
French Guiana hosts large blocks of remote forests, but as most of Amazonian countries face growing pressures. Methological tools targeted to guide sustainable land management considering both human needs and biodiversity conservation are needed. For this purpose, the human footprint was developped using GIS informations on human settlements, roads, forest uses, and land occupation. The result is a map of scores expected to resume the distribution and strength of threats. To test how the footprint give a reliable overview of pressures faced by biodiversity, these scores were crossed with a set of fauna data and direct description of threats, including hunting pressures, monkeys and large birds communities, otter, tapir and caimans abundances, and fish assemblages. Richness and abundances of many large species, including large monkeys, frugivorous birds, caimans and tapirs were negatively correlated with the scores, although abundances of otters and fish assemblages were not. Similarly, sustainability of hunting was not a priori explained by footprint scores. The footprint map appears to be a rough surrogate of threats faced by many species, and could usefully help to identify, at the country scale, areas where biodiversity is expected to face highest pressures. But the footprint has two major limits. It lacks of reliability at more local scales, being unable to discriminate fewly disturbed animal communities, and then would have to be associated with field surveys. Second, the footprint is based on radial decreasing gradients from expected disturbance sources, and for this reason lack of reliability for identification of pressures with a longitudinal gradient, such as rivers pollution. Similarly, catchment areas of hunters are not regularly distributed around settlements, and sustainability of hunting cannot be estimated by the score of the area. Last, potential wildlife flows between source and sink areas are not considered. Although the footprint has to remain a simple and easy tool, some improvements are required, sincluding a better definition and associated scores of pressures, and an obvious need to balance the score of a given site according to the scores of the surrouding areas.