How bad is the current Amazon drought?

It could be the worst Amazon drought ever because of two climatic phenomena fueled by climate change. The first is El Niño, the abnormal warming of the surface waters of the central-eastern equatorial Pacific Ocean. It happens every two to seven years, and is expected to peak in January or February and last until May—a year since the drought began. The second phenomenon is the Atlantic Multidecadal Oscillation (AMO), the abnormal warming of the surface water of the tropical north Atlantic. Because of these two phenomena, the drought will have a severe impact on the next Amazon dry season, from June to December of 2024, because much less rain is expected during the next Amazon rainy season, from January to May of 2024. This rain shortage will impact groundwater storage to feed and replenish rivers and provide water to trees, stressed by the current drought, that need to withstand the next dry season. It is unusual for these two events to be very intense at the same time. When they have occurred together they have tended to differ in their intensities.

What areas are being hit hardest and how?

The areas of the Amazon most affected by the drought are the southwest and northwest Amazon, which are usually affected by both El Niño and AMO, as well as the banks of the Amazon River. The east and southeast Amazon are the biome’s least affected areas this year. Among the first signs this drought would be severe was the death of thousands of fish throughout the Amazon and 150 dolphins in Lake Tefé, in Amazonas state, from late September to mid-October. The drought’s major environmental impact has been the death of this aquatic wildlife, widespread tree mortality, and, more recently, widespread forest fires. Amazon dwellers have been devastated by massive die-offs of fish, their main protein source, and falling water levels that have compromised the navigability of rivers, the only means for remote Amazon communities to get goods to and from markets. Water security has been compromised by pollution from dead and rotting fish. And with greater sediment concentrations in now-shallower rivers, filters are needed to make river water drinkable. And the health of Amazon people is impacted not only by poor water quality, but also by poor air quality due to wildfire smoke.

Does deforestation have a role?

Amazon deforestation worsens drought indirectly by increasing greenhouse gas (GHG) emissions, which fuel global warming. It worsens drought directly by impacting the local microclimate, increasing the surface temperature of deforested areas, and creating more ignition sources for fires in a very dry rainforest. The consequences of this year’s drought would have been much worse if the deforestation rate had not declined due to enforcement efforts launched by Lula [President Luiz Inácio Lula da Silva]. That said, stopping Amazon deforestation is key to reducing the severity of forest fires, most of which are caused by fires that escape control after being set to conduct slash-and-burn farmland clearing. And stopping illegal deforestation of Amazon riverbanks is also key, since land clearing in those areas causes silting of waterways, making them shallower and quicker to dry during droughts.

Is aggressive reforestation required as well?

Reforestation in the Amazon and other Brazilian biomes is very important, especially along riverbanks, for the reasons I mentioned above. But active reforestation—where trees are planted, a process which differs from passive reforestation, where trees grow from seeds provided by seed banks [seed depositories that preserve genetic biodiversity]—has been slow because of insufficient public and private funds. And more companies need to be involved in producing seeds and growing seedlings to build up a strong reforestation supply chain.

Has the drought caused more Brazilian Amazon fires?

Overall, there have been fewer wildfires in the biome this year compared to last year. This is because Brazilian Amazon deforestation this year declined due to government action to curb slash-and-burn land clearing. As a result, fewer of these burns escaped control, which is often how wildfires get started in that biome. But although there have been fewer wildfires, more land area has been affected by wildfires this October, which to this point has been the height of the drought, than last October, largely because of the dry conditions.

How has the drought affected Brazil’s greenhouse-gas emissions?

GHG emissions related to thermoelectric plants have increased as these fossil-fuel plants have stepped up production to offset drought-related declines in Amazon hydroelectric output. More emissions are being generated due to the decomposition of organic material exposed in waterways whose levels have fallen because of the dry conditions. And still more GHG emissions will result from decomposition related to large-scale tree mortality caused by the drought. So for these reasons there will be a net increase in GHG emissions this year due to the reasons mentioned above—more fossil-fuel-based electricity, more trees dying due to drought, and more land area impacted by forest fires, even though there were fewer fires as a whole in the biome.