Anthropogenic activities on mangrove areas (São Francisco River Estuary, Brazil Northeast): A GIS-based analysis of CBERS and SPOT images to aid in local management

Abstract

In Brazil, despite the existence of various environmental laws to protect mangroves, this ecosystem has been affected by a variety of anthropogenic activities. The São Francisco River Estuary (SFRE, Brazil Northeast) comprises significant mangrove forests, important for human populations, and is included in an Environmental Protected Area of sustainable use which does not have a management plan. This work assessed and mapped anthropogenic activities on the mangroves of this estuary and provided a number of guidelines for a local management plan. Satellite images (SPOT 5 and CBERS 2B) of 2008 were processed and a land use/cover map (study area size: 192.4 km²) produced and verified by fieldwork. About 93% (178.8 km2) of the study area is occupied by natural cover such as: sandy coastal vegetation (147.3 km2, 77%), mangroves (30.1 km2, 15.7%) and intertidal flats (1.4 km2, 0.7%), while 7% (13.6 km2) is occupied by human activities as aquaculture (4.5 km2, 2.4%) and agriculture (9 km2, 4.7%). These uses are spatially distributed within mangroves, accounting for approximately one quarter (7.8 km2) of its area, which may indicate the conversion of these forests. Shrimp farming is the main anthropogenic activity, occupying the highest area and occurring within the tallest Rhizophora mangle forests (tree height >15 m). We recommend that a management plan for the SFRE considers: the implementation of sustainable aquaculture practices (e.g. small-scale without deforestation of mangroves, use of native species, effluent treatment, socio-economic equity), strategies for the compliance of the laws regarding shrimp farming license and operation and support the creation of community-based cooperatives for the execution of sustainable aquaculture.