Deforestation and Forest Fires in Roraima and Their Relationship with Phytoclimatic Regions in the Northern Brazilian Amazon

Abstract

Deforestation and forest fires in the Brazilian Amazon are a regional-scale anthropogenic process related to biomass burning, which has a direct impact on global warming due to greenhouse gas emissions. Containment of this process requires characterizing its spatial distribution and that of the environmental factors related to its occurrence. The aim of this study is to investigate the spatial and temporal distribution of deforested areas and forest fires in the State of Roraima from 2000 to 2010. We mapped deforested areas and forest fires using Landsat images and associated their occurrence with two phytoclimatic zones: zone with savanna influence (ZIS), and zone without savanna influence (ZOS). Total deforested area during the interval was estimated at 3.06 × 10(3) km(2) (ZIS = 55 %; ZOS = 45 %) while total area affected by forest fires was estimated at 3.02 × 10(3) km(2) (ZIS = 97.7 %; ZOS = 2.3 %). Magnitude of deforestation in Roraima was not related to the phytoclimatic zones, but small deforested areas (≤17.9 ha) predominated in ZOS while larger deforestation classes (>17.9 ha) predominated in ZIS, which is an area with a longer history of human activities. The largest occurrence of forest fires was observed in the ZIS in years with El Niño events. Our analysis indicates that the areas most affected by forest fires in Roraima during 2000-2010 were associated with strong climatic events and the occurrence these fires was amplified in ZIS, a sensitive phytoclimatic zone with a higher risk of anthropogenic fires given its drier climate and open forest structure.

Climatic and anthropogenic drivers of northern Amazon fires during the 2015–2016 El Niño event

“…, Barni et al. ). In the 1997–1998 El Niño event, approximately 11,000 to 14,000 km 2 of forests were burned in the state of Roraima, an area equivalent to 7.4–9.0% of its forest cover and over twice as large as the total deforested area in the state up to 1997 (Barbosa and Fearnside ).…”

“…Barni et al. () estimated that 3.06 × 10 3 km 2 has been deforested and 3.02 × 10 3 km 2 of forests have burned between 2000 and 2010 in Roraima. These authors found that 98.5% of the forest area affected by fire was burned in years with El Niño events.…”

“…The synergy between intense drought events and modern human activities may be causing new changes in the landscape dynamics and in the carbon emissions from this region (Barbosa and Fearnside 1999, Bush et al 2008, Barni et al 2015b). In the 1997-1998 El Niño event, approximately 11,000 to 14,000 km 2 of forests were burned in the state of Roraima, an area equivalent to 7.4-9.0% of its forest cover and over twice as large as the total deforested area in the state up to 1997 (Barbosa and Fearnside 1999).…”

“…Furthermore, secondary vegetation growing in previously deforested areas is highly prone to accidental fires given its short and opened canopy (Ray et al 2005), mostly in its early regeneration stages and in dry years (Guti errez-V elez et al 2014). Barni et al (2015b) estimated that 3.06 9 10 3 km 2 has been deforested and 3.02 9 10 3 km 2 of forests have burned between 2000 and 2010 in Roraima. These authors found that 98.5% of the forest area affected by fire was burned in years with El Niño events.…”

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

“…In addition to the above mentioned factors, the dynamics of the impacts of fire on savannas (Barbosa & Fearnside, 2005), and primary forests in Roraima State (Barni, Pereira, Manzi, & Barbosa, 2015) is, in part, a reflection of the long-established culture of slash-and-burn as a form of agricultural land management (Barbosa & Fearnside, 1999). This action has a singular impact on a local ecosystem, as it is associated with the effects of climate change (Gustavsson et al, 2017), and can increase the likelihood of extreme climatic events linked to either aridity or rainfall.…”