The river basin contains the largest rainforest in the world, making it a global hotspot of biodiversity and a key part of the global hydrological and carbon cycle. The river levels are reported to be at lowest levels in 120 years, threatening the estimated 30 million people living in the Amazon basin across several nations including Brazil, Peru, Colombia, Venezuela, Ecuador and Bolivia, by disrupting transportation, isolating communities and killing wildlife.
The large riverine system powers significant portions of the affected countries’ energy through hydropower, with Brazil relying on hydro power for 80% of its electricity, Colombia 79%, Venezuela 68%, Ecuador and Peru 55%, and Bolivia 32% (USaids, 2018). The drought is significantly impacting dam capacities and energy output and led to power cuts in the region as early as June 2023.
Scientists from Brazil, the Netherlands, the UK and the US used published peer-reviewed methods to assess whether and to what extent the drought has been influenced by climate change as well as the occurrence of El Niño, which is known to be associated with drought in the Amazon. While the drought started earlier in the west of the basin, the whole basin has been in severe or exceptional drought for the second half of the year (Fig. 1 blue outline).
There are several ways to characterise a drought. Meteorological drought considers only low rainfall, while agricultural drought combines rainfall estimates with evapotranspiration. Increased evapotranspiration due to regional warming can play a major role in exacerbating drought impacts. In this study we assess agricultural drought as well as meteorological drought. The main variable used here to characterise agricultural drought is the Standardised Precipitation Evapotranspiration Index (SPEI) (figure 1) which uses the difference between rainfall and potential evapotranspiration to estimate the available water. The more negative the values are, the more severe the drought is classified. Meteorological drought is analysed here using an index (SPI) based on precipitation alone.
