Climatic seasonality and land use dynamics in the Brazilian Amazonia
E. O. C.
Aragao, UNIVERSITY OF OXFORD, email@example.com
Barbier, UNIVERSITY OF BRUSSELS, firstname.lastname@example.org
Lima, INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS, email@example.com
Malhi, UNIVERSITY OF OXFORD, firstname.lastname@example.org
Shimabukuro, INSTITUTO NACIONAL DE PESQUISAS ESPACIAIS, email@example.com
Anderson, UNIVERSITY OF OXFORD, firstname.lastname@example.org
Saatchi, NASA - JET PROPULSION LABORATORY, email@example.com
Understand the interplay between climate and land use dynamics is currently a fundamental concern for assessing the vulnerability of Amazonia to climate change. Some models have predicted climate change causing increased drought frequency in Amazonia. Drought may have direct impacts on vegetation phenology, physiology, structure and composition of Amazonian forests. In addition, conditions associated with intense forest degradation by logging and deforestation can dramatically increase the risk of fires in this ecosystem. Here we analyse satellite derived monthly and annual time-series of rainfall, fires and deforestation to explicitly quantify the seasonal patterns of these three variables and their relationships in the Brazilian Amazonia, with a particular focus on the Amazonian drought of 2005. Our results demonstrate a marked seasonality for all variables with the peak of deforestation and fire pixels occurring during the dry season in Amazonia. The majority of the fires in Amazonia are likely to be associated to land use practices, as 60% of the total number of detections in 2005 occurred in deforested areas. The spectral analysis showed for an annual periodicity a correlation >90% among all time series analysed. We found a strong linear relationship (r2=0.84, p=0.004) between hot pixels counts and the size of the area deforested annually from 1998 to 2004, which may be due to the expansion of pastures and large areas of mechanized agriculture in the southern part of Brazilian Amazonia. However, during the 2005 drought, we found that the number of hot pixels increased 43% in relation to the expected value for a similar deforested area (~19,000 km2). Based on this result we estimated that during an exceptional dry year, such as 2005, the rate of hot pixels detections per km2 of deforested area annually would increase from 8.5 to 14.8. Therefore, the combined effect of land uses, such as deforestation, logging and fire and its interactions with climate is a realistic threat for Amazonian rainforest and consequent stability of the global carbon cycle and the climatic system.
Science Theme: LC (Land Use and Land Cover Change)