Threats to the Cerrado remnants of the state of São Paulo, Brazil

Abstract

Patches of natural vegetation remaining in landscapes occupied by man are continuously under threat due to the edge effects and also to land use types around these remnants. The most frequent threats and land use types in the vicinity of 81 Cerrado (tropical savanna type) fragments in the State of São Paulo, Brazil, were analyzed in order to verify if the frequency of every type of disturbance to the natural ecosystem depends on the neighboring land use. The hypothesis of the study assumes that environmental threats are correlated with land use around protected areas. From the 81 areas, the most frequent human-induced land cover types around the Cerrado remnants were: pasture (recorded in 78% of the areas), sugarcane plantations (26%), roads (19%), annual crops and reforestation (14% each). The most frequent sources of threats were invasive grasses (35% of the areas partially or totally invaded) and cattle (observed in 32% of the areas), followed by deforestation (21%), and fire (21%). The chi-square analysis revealed that, with the exception of deforestation, which does not depend on land use, all other threats are influenced by the neighboring land use. The occurrence of invasive grasses and fires are strongly favored by the presence of roads and urban areas. Sugarcane, reforestation, and permanent crops were the less impacting land use types found in the study area, when only considering impact frequency. These land use types have fire and weed control, and also exclude cattle, indirectly protecting natural ecosystems. Key words: savanna, conservation, impact, fragmentation, land use AMEAÇAS A FRAGMENTOS DE CERRADO NO ESTADO DE SÃO PAULO, BRASILRESUMO: Fragmentos remanescentes de vegetação natural em paisagens antropizadas sofrem ameaças permanentes, devido aos efeitos de borda e às atividades antrópicas nas áreas limítrofes. Para verificar a hipótese de que o tipo de ameaça ao ecossistema e a sua freqüência dependem do uso da terra no seu entorno, foram analisados 81 fragmentos de Cerrado no estado de São Paulo. Para cada fragmento foram registrados os tipos de perturbação no ecossistema e os tipos de uso da terra no seu entorno. Os usos mais freqüentes foram pastagens cultivadas (registradas em 78% das áreas), plantio de canade-açúcar (26%), rodovias (19%), reflorestamento (14%) e culturas anuais (14%). As ameaças mais freqüentemente registradas foram gramíneas invasoras (35% das áreas parcial ou totalmente invadidas), presença de gado (32%), desmatamento (21%) e fogo (21%). A análise da freqüência observada de cada tipo de impacto mediante a freqüência esperada caso não houvesse influência do uso da terra (qui-quadrado), mostrou que as ameaças dependem do uso da terra nas áreas ao redor dos fragmentos, exceto para o desmatamento, que tem ocorrido indiferentemente ao tipo de uso. Gramíneas invasoras e fogo são muito mais freqüentes na vizinhança de rodovias e zonas urbanas, enquanto que o plantio de cana-de-açúcar, silvicultura e fruticultura têm sido os usos da terra menos impactantes para a vege...

Woody encroachment and its consequences on hydrological processes in the savannah

“…In the whole state of São Paulo, the use of fire on native vegetation has been prohibited by law since the year 2000. On private properties, farmers also protect their land from fire when used for crops, silviculture or pasture with exotic grasses [39]. Under these land uses, fire is negative, as it destroys what has been cultivated, including the dry biomass of exotic grass that is eaten by cattle in the winter.…”

Agriculture, habitat loss and spatial patterns of human occupation in a biodiversity hotspot

“…Durigan et al, 2007), up to almost 100% (at our grid resolution) of natural cover in the northern areas. Although the amount of habitat loss may be dependent of data sources and techniques, it is unlikely that they provide very different maps at the broad-scale resolution used in the analyses performed here.…”

Habitat use by Collared Crescentchest (Melanopareia torquata) in a Cerrado in southeastern Brazil: implications for management

“…Currently, it represents only 0.81% and occurs in small isolated fragments (Durigan et al, 2007). This study was conducted in the Cerrado of Estação Ecológica de Itirapina (EEI), in the cities of Itirapina and Brotas (22° 15' S and 47° 49' W) including an area of 2,720 ha (Figure 1).…”