Abstract
Tropical forests are known for hosting about half of the global biodiversity, and therefore are considered to be a fundamental part of the Earth System. However, in the last decades, the anthropogenic pressure over these areas has been continuously increasing, mostly linked to agricultural expansion. This has created great international concern, which has crossed the limits of national policies. A clear example was the last crisis suffered this year (2019) in the Amazon, and in general, in tropical South America (SA), due to the increasing fire activity in the region, which is strongly linked to deforestation and forest degradation. International media extensively informed the world about fire activity based upon active fire data, which provided quick but incomplete information about the actual fire-affected areas. This short paper compares fire occurrence estimations derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) data of active fires and from burned area products for the first 10 months of 2019 in SA. Results show a significant increase in fire activity over the full-time series (2001–2018) in Bolivia, Paraguay and Venezuela, while Brazil shows a much higher BA than in 2018, but with values around the average burned area of the whole time series.
Highlights
Satellite Earth data is an ideal tool to estimate the extent and impacts of different natural and human-caused hazards, as it provides a global and systematic observation of ground conditions at different spatial, spectral and temporal resolutions
Bolivia tripled the burned areas (BAs) of 2018 (48,187 versus 15,448 km2), and it exceeded by 51% the average of the time series (31,819 km2). 2019 was clearly worse than 2018 in Venezuela (24% more BAs, with 44% above time-series average), and in Paraguay (69% more BAs, but in this case very close to the average of the times series)
The analysis of areas burned in 2019 in South America shows similar spatial trends to what was already observed with active fires (AFs) in near-real-time, BA estimations are generally higher
Summary
Satellite Earth data is an ideal tool to estimate the extent and impacts of different natural and human-caused hazards, as it provides a global and systematic observation of ground conditions at different spatial, spectral and temporal resolutions. Satellite images provide an objective estimation of actual fire occurrence, either by observing the thermal anomalies caused by active fires (AFs), or by detecting the changes in surface reflectance as a result of vegetation burning or scorching. The former approach is based on the high increment of ground emittance in the middle infrared (around 3.5 μm) caused by the high fire temperatures. This facilitates the detection of AF pixels as well as the energy they release (often termed fire radiative power (FRP)) [2]. The spectral contrast of burned and unburned signal is less sharp than the thermal anomaly, and burned pixels may be confused with other seasonal changes
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