A new study has warned that human interventions may have accelerated the rate of organic matter decomposition in rivers and streams globally. According to the study, published on May 30 in the journal Science, this could pose a threat to biodiversity in waterways worldwide and increase the amount of carbon in the Earth’s atmosphere, potentially exacerbating climate change.
Researchers of this study claim it is the first to combine global experimentation and predictive modeling to illustrate how human impacts on waterways can contribute to the global climate crisis.
Human Interventions
Rivers and streams provide much more than just beautiful landscapes or summer relaxation spots; they are a crucial part of the planetary system that determines the amount of carbon stored in the soil or released into the atmosphere. When tree debris falls into a waterway, it fuels the entire ecosystem, as microorganisms feed on the debris, fish consume it, or it settles on the riverbed where carbon is trapped.
However, human activity can accelerate the decomposition of leaves and other debris, releasing more carbon dioxide into the atmosphere. For instance, chemicals in fertilizers, such as phosphorus and nitrogen, feed microbes and lead to faster decomposition of organic matter.
In the study, standardized cotton strips were sent to over 150 researchers in 40 countries. Instead of the tree leaves usually used to measure organic decomposition rates in 550 local waterways, researchers combined these field samples with comprehensive datasets to create a machine learning algorithm that estimates decomposition rates worldwide, according to a press release on EurekAlert.
The rate at which leaves decompose in waterways serves as an indicator of the level of risk associated with climate changes (Shutterstock)
Study co-author Krista Capps, an assistant professor of aquatic biology at the University of Georgia, stated, “The shocking thing about our data is that even though we chose relatively low-impact sites, we could still see hotspots where humans had a real impact, either through urban expansion or agriculture or a mix of both.”
Capps added in an interview with Al Jazeera that the global map resulting from this modeling illustrates the harmful effects of human activity. For example, parts of the central United States, southern Canada, and Europe—regions with high population density and urban and agricultural development—were hotspots for rapid decomposition of the strips used in the field experiment, strongly indicating human activity on a continental scale and clear impacts on the carbon cycle in rivers.
Accelerating Climate Change
According to the study, the rate at which leaves decompose in waterways is an indicator of the level of risk associated with climate changes. Capps explained that the implication of leaf decomposition in river streams is that we can no longer rely on water bodies—including rivers, streams, and lakes—to retain carbon as effectively as they used to.
Capps emphasized that researchers have studied decomposition and its relationship to climate in the past, and integrating this data into a predictive algorithm fills significant gaps in our understanding of climate changes, particularly in regions like the tropics and remote or hard-to-reach areas where data collection can be challenging.
The global map created using the algorithm also provided relevant results closer to home. For example, the map shows a clear gradient from north to south in Canada, with decomposition rates slowing down as temperatures drop. This variation is also related to the types of trees thriving in these environments.
As part of the study, researchers modeled natural litter decomposition rates compared to cotton farming ranges and found that pine tree debris decomposes more slowly than oak tree debris. With rising climate temperatures, dense deciduous forests (oak) may spread northward, leading to potentially higher decomposition rates and more carbon release into the atmosphere.
Researchers noted that among the areas requiring the most attention are parts of the world like the northern Canadian forests, currently the world’s lowest on the decomposition scale. Northern latitudes are warming much faster than southern latitudes, so these rapidly changing areas will be of greater importance in the future.
For more details, visit our website dzwatch.dz. Human Interventions in Waterways.
