When Wetlands Dry Up: Projecting the Amazon's Future Under Climate Change

The Amazon Basin—home to the largest tropical wetland system on Earth—is facing an uncertain hydrological future. As the planet warms, these critical ecosystems, which regulate carbon, support biodiversity, and buffer floods, are at risk of shrinking or disappearing altogether. A recent study published in PLOS Water titled “Future Amazon basin wetland hydrology under projected climate change” provides the most detailed glimpse yet into how climate change could reshape the Amazon's vast wetlands by the end of the century.

Led by researchers from the UK Met Office and Brazil’s disaster monitoring center (CEMADEN), the study uses high-resolution hydrological modeling to simulate changes in flood extent and duration under a warming scenario of +4 °C—a plausible outcome without significant mitigation efforts.

A Shrinking Lifeline: The Importance of Amazonian Wetlands

Wetlands in the Amazon play a pivotal role in maintaining ecological balance. They:

• Absorb and store floodwaters, reducing disaster risk
• Support complex food webs, including fish, birds, and aquatic plants
• Sequester carbon, slowing the pace of global warming

Despite their importance, little was known about how these systems would respond to sustained climate stress—until now. The study aims to answer a key question: How will projected climate change affect the extent, timing, and variability of wetland flooding in major regions of the Amazon Basin?

Modeling the Future: Methods Behind the Projections

The research team modified the JULES (Joint UK Land Environment Simulator) land surface model to better represent both fluvial (river-driven) and interfluvial (rainfall-driven) flooding. Using six climate scenarios from HadGEM3—a global climate model—the team examined how a +4 °C warming world would alter hydrology in four distinct Amazonian wetland zones:

• Roraima (north)
• Manaus (central-east)
• Iquitos (west)
• Llanos de Moxos (south)

Each scenario incorporated projected changes in precipitation patterns, surface temperatures, and sea-surface temperature feedbacks. Observational data from satellite missions like GIEMS and SWAMPS were used to calibrate and validate the model outputs.

What They Found: Key Results and Regional Variations

1. Overall Reduction in Flooded Areas

The model predicts an average 11% decline in total flood extent across the Amazon Basin by 2100, with some scenarios suggesting losses up to 36%. A few wetter simulations even showed slight increases (+9%), highlighting the high degree of uncertainty tied to future rainfall patterns.

2. Duration of Flooding Drops Dramatically

In Roraima and Manaus, flood seasons could shrink by up to 10 months, drastically altering seasonal cycles vital for fish spawning, nutrient exchange, and agriculture.

3. Iquitos: A Case of Extremes

Predictions for Iquitos in Peru varied widely:

• One simulation projected a 53% reduction in flooded area.
• Another showed a 12% increase—a stark illustration of how sensitive the region is to rainfall variability.

4. Llanos de Moxos: Milder Declines

This southern region of Bolivia may fare better, with more modest projected decreases in flood extent ranging from 11% to 17%.

Drivers of Change: Climate Dynamics and CO₂ Effects

The projected decline in flood extent stems from shifting rainfall patterns, primarily influenced by sea surface temperature anomalies in the Pacific and Atlantic Oceans. Warmer temperatures also lead to higher evapotranspiration rates, though this effect is dampened somewhat by elevated CO₂ levels, which reduce stomatal conductance in plants.

As a result, less water is available to feed floodplains, especially during the dry season.

“Wetlands act as sponges for rainfall and rivers. When they shrink, the entire Amazon system becomes more fragile,” explains lead author Nic Gedney.

Consequences: Ecological, Economic, and Political

The implications of these changes are vast and far-reaching:

• Biodiversity loss: Fish, amphibians, and plants adapted to seasonal flooding may face habitat collapse.
• Fisheries and farming: Local communities dependent on aquatic ecosystems could suffer major livelihood disruptions.
• Carbon storage: Shrinking wetlands may reduce the Amazon’s ability to sequester atmospheric CO₂.
• Fire and drought risk: Drier landscapes are more susceptible to wildfires, compounding environmental stress.

In regions like Peru and Bolivia, these shifts could exacerbate existing challenges, including water scarcity, agricultural decline, and increased exposure to extreme weather.

From Forecast to Action: What Needs to Be Done

The authors recommend several urgent policy and research priorities:

1. Improve regional climate models to reduce uncertainty in rainfall projections.
2. Invest in local hydrological monitoring using satellites, drones, and in-situ sensors.
3. Integrate wetland risk scenarios into national adaptation strategies, especially for agriculture, water planning, and disaster response.
4. Enhance transnational cooperation among Amazonian countries to coordinate flood management and conservation.

“Predicting flood behavior is not enough. We must act on this knowledge to protect communities and ecosystems,” emphasizes co-author Conrado Rudorff.

Conclusion: The Clock Is Ticking on Wetland Resilience

This study represents a breakthrough in our understanding of Amazonian hydrology under climate stress. But its message is clear: without swift and coordinated action, the Amazon’s wetlands—and the services they provide—may not survive the century.

For policymakers, conservationists, and local communities, the path forward involves not just better science, but bolder decisions about climate, land use, and water governance. The Amazon’s future hinges not only on rainfall, but on human resolve.

Topics of interest

Climate Biodiversity