South America: Surplus emerges in the Amazon, deficit continues in Brazil, Guianas

27 May 2025

THE BIG PICTURE
The forecast for the 12 month period ending in January 2026 indicates that widespread exceptional deficits will significantly diminish in size, but remain in portions of Brazil and the Guianas. Severe to exceptional surpluses will emerge in portions of the Amazon Rainforest and the Bolivarian Nations.

Severe to exceptional deficits are expected in:

Central and eastern Brazil, with exceptional deficits appearing in western, central, and southern areas of Mato Grosso, northeastern Amazonas, Roraima, Mato Grosso do Sul, and across central areas of Para and Maranhao.
Isolated portions of the Guianas. Further west, much of south-central and eastern Venezuela will observe
Argentina, spreading throughout northeastern areas of the country, specifically near the city of Cordoba. Paraguay will also observe severe deficits north of the city of Asuncion.
Chile, in pockets of northern and central areas of the country.

Severe to exceptional surpluses are anticipated in:

Western Brazil, across much of central and southwestern Amazonas.
Western Bolivia, with the most intense anomalies occurring near the city of La Paz.
Southern Peru, in areas west of Lake Titicaca.
Central portions of Ecuador, in areas near the city of Quito.

Transitional conditions are predicted to occur in:

Much of the Guianas, primarily in central Suriname and French Guiana.

The 3-month maps (below) show the evolving conditions in more detail.

FORECAST BREAKDOWN
The forecast through July 2025 indicates that exceptional deficits will occur in Suriname and French Guiana, as well as in several pockets of central to southern Brazil. Pockets of exceptional deficits are also expected in east-central Venezuela, central Colombia, central to southeastern Peru, and in regions along the borders of northwestern Argentina, southern Paraguay, and western Rio Grande do Sul in Brazil. Exceptional surpluses are expected in regions near Bolivia’s city of La Paz. Moderate to severe surpluses are expected in areas of Brazil’s Amazonas and Acre states.

From August through October 2025, exceptional deficits will increase in size throughout central and southern Brazil, as well as along northern coastal areas. These anomalies continue west, covering much of the Guianas and western Venezuela. Further west, exceptional deficits are expected to emerge throughout regions southeast of Lake Maracaibo, appearing near the city of El Vigia and continuing southeast into central to southwest Colombia. These anomalies spread through Ecuador into pockets of central Peru. Exceptional deficits are expected to occur in southern coastal regions of Argentina. Severe to exceptional surpluses are anticipated throughout areas of southwestern Bolivia in the Oruro Department.

The forecast for the final months – November through January 2026 – indicates that exceptional deficits in southern and central Brazil will resolve. Severe to exceptional deficits will continue in northern coastal regions of the Guianas, central and northern coastal Venezuela, and in southeastern Peru near the Manu Province. Regions along portions of Argentina’s southern coast may observe exceptional deficits. Central to southern Chile will observe moderate to severe deficits. Moderate to severe surpluses are expected to continue in areas along the northern border of Argentina, southern Bolivia, and southeastern Peru.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
In 2024, 6.7 million hectares of tropical forests were lost, an amount nearly equivalent to the size of Panama, with a significant portion caused by fires. The fires were fueled by record heatwaves and drought, especially in Latin America. Brazil, with the world’s largest tropical forest, saw six times more fire-related loss than in 2023 due to its worst drought in 70 years. Bolivia followed as second in the world for total tropical forest loss. Other Latin American countries hit by fire include Peru, Colombia, Guyana, Mexico, Belize, Guatemala, and Nicaragua.

A recent study analyzed the cause of severe lows in Lake Titicaca’s water levels from 1923 to 2023 in an effort to increase resilience of Peru and Bolivia’s ecosystems and drinking water. After examining 16 major low-water events, researchers concluded that a key factor in these long-term drops is a reduction in moisture coming from the Amazon region. Additionally, they found that some of these events are short (lasting 4 months or less), and caused by brief changes in weather, while most are long-lasting (over 2 years), and are linked to larger climate patterns like sea surface temperatures and shifts in wind and moisture flow.

Scientists ran a 21-year experiment from 2002 to 2023 to study the effects of long drought in the Amazon rainforest and drought-induced biomass loss. The study found two main phases in the 21 year period. In the first phase, from 2002 to 2016, the forest lost about a third of its tree mass, mostly from the death of big trees. There was less water available for the trees, and the forest lost more carbon than it was gaining through new growth. In the second phase, from 2017 to 2023, the forest stopped shrinking and began to stabilize. Water availability per tree improved because there were fewer large trees competing for it. After years of drought, the forest started to recover, but only after losing many big trees.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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