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Monday May 06, 2024 at 12:25

River degradation can worsen the climate crisis

A new study shows that the sum of several human impacts on rivers increases the concentration of greenhouse gases in their waters, potentially aggravating the climate crisis.

Writing / Irene Vega

The work, led by the Biodiversity and Conservation Area of ​​the Rey Juan Carlos University, has analyzed how the concentration of two gases responsible for the greenhouse effect, carbon dioxide and methane, responds to the accumulation of three types of human impact, including the increase in nitrates, the increase in temperature and the deoxygenation of the waters. The results of the study show that these impacts, together, can double the concentration of these greenhouse gases in river waters.

"Although rivers, naturally, tend to have a higher concentration of carbon dioxide and methane than the atmosphere, this work demonstrates for the first time that the sum of several human impacts increases the concentrations of these gases and, potentially, their emissions." to the atmosphere,” he points out. Cayetano Gutierrez, researcher at the Rey Juan Carlos University (URJC) and first author of the published study in the scientific journal Global Change Biology.

To carry out this research, in which the Center for Molecular and Environmental Biology of the University of Minho - (CBMA-UMinho), the University of Barcelona (UB) and the Center for Ecological Research and Forest Applications (CREAF) have also participated, Greenhouse gas samples and measurements of metabolism and human impacts were collected in 50 rivers in northern Portugal.

Using this data, the research team also analyzed how the spatial scale at which environmental degradation occurs influences, evaluating impacts at the basin scale compared to those that occur at the local level.

“Our results indicate that the scale of human impact influences carbon dioxide and methane concentrations differently. Carbon dioxide, which is a more soluble gas than methane, can travel long distances in rivers and appears to respond to impacts that occur at different points in the basin, such as agricultural intensification or urban discharges. However, our models suggest that methane, which is less soluble and quickly escapes into the atmosphere, responds to both local impacts and others that occur at the basin scale," he says. Daniel von Schiller, author of the work and professor at the UB.

This study has important implications for river management, where restoration and impact mitigation measures tend to focus on local actions, which do not consider basin-scale impacts or benefits for climate stability. In this sense, one of the current focuses of river management would be to reduce the presence of nitrates, which come from agricultural activity and can cause serious ecological crises, such as the one that occurred in the Mar Menor. "The results of this study suggest that reducing the presence of nitrates and the deoxygenation processes of water could offer additional benefits to those already known, and could contribute to the fight against climate change," he indicates. Claudia Pascoal, professor at CBMA-UMinho and senior author of the work. “Our results reinforce the need to manage rivers at the basin scale, with a comprehensive vision, not only to preserve biodiversity and the benefits they bring to society, but also to prevent the climate crisis from worsening,” concludes Pascoal.