Anthropic Processes and Land-Use Change During 33 Years in Roraima, Northern Amazonia

Abstract

The Amazon region has experienced a rapid rate of deforestation and land use change as a result of establishment of agricultural settlements, resulting from public policies designed to promote rural development. We analyzed land use patterns and changes in the central region of Roraima, northern Brazil, testing the hypothesis that the anthropic pressure based on the conversion of natural vegetation (forest ecotone zone and open areas of savanna and campinaranas) on agriculture and pasture, has led to the decline of forest resilience, and has not promoted development in lands converted in agricultural colonization projects, a process exacerbated by practices of burning. Satellite images from between 1984 to 2017, with field-collected data and geoprocessing techniques, allowed interpretation and analysis of seven land-use classes. Agriculturally-based human impacts were greatest in forest areas, with forest loss rates being 6.4 times greater than regeneration rates. The 39.3% reduction in natural non-forest vegetation types exceeded that of forest loss (23.8%). Repeated fires resulted in a 627.1% increase in forest fragmentation in areas heavily impacted by fire. Our study revealed that, over 33 years, deforestation and transitions of land to non-conservation uses did not lead to a system with highly productive agricultural practices, but to extensive impoverished, and degraded subsistence. The main reason was the basic unsuitability of the region´s extremely acidic/dystrophic soils on which settlements have been founded, and the predominance of low-tech, family-based, agriculture and the absence of the required technology for attaining better results.

Illegal Selective Logging and Forest Fires in the Northern Brazilian Amazon

“…Tree mortality and reduced stocks of forest carbon within Flona Anauá were more intense in the eastern region, due to the proximity of the area to rural roads and a federal highway (BR-174), where agrarian reform settlement projects, private rural properties, and ADs are located. For years, the use of indiscriminate fire by humans has been part of the conversion of land use in Roraima [56]. The State of Roraima still has a large stock of forest biomass (see 176 p. [57]), but the association of selective logging and forest fires has contributed to the drastic loss of carbon in endemic Amazonian ecosystems, and increased greenhouse gas emissions [40].…”

“…Soil carbon in these ecosystems percolates to groundwater, giving rise to the dark waters observed in the Itapará River and several igarapés of the west region of Flona Anauá. Where accessible to humans, the campinaranas have been used, unsustainably [21,56], for sand extraction, timber exploitation, agriculture, and livestock farming, leading to frequent forest fires [38].…”

Análise Temporal do Uso e Cobertura do Solo na Região do Apiaú no Estado de Roraima, Brasil: um estudo preliminar

“…Possui o limite com 466.138 ha de área, sendo 312.723 ha o somatório da área de Floresta Estacional Dossel Uniforme, Floresta Ombrófila Densa Dossel Emergente, Capoeira, áreas em regeneração, vegetações de várzeas e 152.985 ha de Pastagem, Urbanizada, Afloramento de Rocha e Água, conforme dados da Figura 2, referente ao ano de 2014. ), e a classificação não supervisionada das mesmas, utilizando-se a ferramenta "Iso Cluster", considerando 10 classes de uso e cobertura do solo (Urquiza et al, 2018).…”

“…As imagens foram escolhidas com base na menor cobertura de nuvens. Após o download, essas imagens foram processadas no software Arcgis 10.1 onde foram realizadas composições coloridas (falsa cor), e a classificação não supervisionada das mesmas, utilizando-se a ferramenta "Iso Cluster", considerando 10 classes de uso e cobertura do solo(Urquiza et al, 2018).…”