Vulnerability of Amazonian forests to repeated droughts

Area of Science:

• Environmental Science
• Ecology
• Climate Science

Background:

• Recurrent extreme droughts in the Amazon have significant socio-economic and environmental consequences.
• Understanding forest vulnerability to repeated droughts is crucial for conservation and management.

Purpose of the Study:

• To investigate the vulnerability of Amazonian forests (both undisturbed and human-modified) to repeated droughts.
• To quantify drought exposure and sensitivity using meteorological and remote sensing data.

Main Methods:

• Assessed meteorological drought using standardized precipitation index (SPI) and maximum cumulative water deficit (MCWD) from 1981-2016.
• Measured forest sensitivity via enhanced vegetation index anomalies (AEVI) from MODIS/MAIAC data (2003-2016).
• Analyzed drought impacts on forest greenness and photosynthetic capacity.

Main Results:

• Severe to extreme drought affected 46% of the Brazilian Amazon in 2015/2016, the largest area since 1981.
• Droughts increased variance in forest photosynthetic capacity, with over 400,000 km² showing reduced capacity.
• The intensity of negative impacts on forest greenness steadily increased from 2005 to 2016.

Conclusions:

• Amazonian forests are becoming more vulnerable to droughts, with impacts intensifying over time.
• Increasingly large forest areas are negatively responding to water shortages.
• These findings highlight the growing threat of drought to Amazonian ecosystems.