Mountain Streams Play a Significant Role in Global Carbon Fluxes: Study
Sat, April 10, 2021

Mountain Streams Play a Significant Role in Global Carbon Fluxes: Study

Rivers and streams are fascinating geological and geographical features. They provide humans and wildlife with sources of food and water / Photo by: Dmitry Pichugin via 123RF

 

Rivers and streams are fascinating geological and geographical features. They provide humans and wildlife with sources of food and water. At the same time, they are capable of effecting massive changes upon the Earth's surface in the form of valleys and canyons formed by erosion. Since rivers and streams can flow for millions of years, it's no wonder that they are remarkably powerful and intriguing.

Aside from helping to produce electricity, up to 65 percent of drinking water comes from these bodies of water. However, just like other natural resources, rivers and streams are also at risk of dying due to the climate crisis. The Ecological Condition Index (ECI) reported that South African rivers worsened between 1999 and 2011. Lowland rivers exhibited the largest drop in the ecological index compared with other river types.

The 2015 Shenandoah Watershed Study, one of the US’ largest and most comprehensive long-term stream chemistry surveys, reported that human processes are affecting mountain streams. According to the University of Virginia, the researchers tracked the impacts of mercury pollution, the climate crisis, acid deposition, and other factors affecting water quality and related ecological conditions in Virginia’s native trout streams.

The findings showed a consistent result: all streams are experiencing increased water temperatures. This can not only affect brook trout populations farther and farther upstream, but the rising temperatures will also shrink their range to the point that some streams will no longer be able to support brook trout populations.

Thus, it is important that we also focus on protecting rivers and streams because these bodies of water protect us against floods, filter pollutants, recycle potentially-harmful nutrients, and provide food and habitat for many types of fish. Previous studies have shown that while small streams may seem meaningless to overall water quality, they are, in fact, the streams most in need of protection.

Why Streams are Important

Many people don’t realize the great benefits that streams offer our planet. Aside from providing an enormous array of habitats for plants, animals, and microbial (bacteria and fungi) life, they also provide a rich resource base for the productivity of stream food webs. According to American Rivers, an organization that combines national advocacy with fieldwork in key river basins to deliver the greatest impact, streams have a significant capacity to store and transform nutrients, including nitrogen and phosphorus.

Previous studies have shown that when downstream waters receive elevated amounts of nitrogen and phosphorus without the ability to store and transform nutrients, this can result in algal blooms and low oxygen in reservoirs and coastal areas. Aside from that, streams are important in flood mitigation and recharging groundwater supplies because they have a huge area in contact with the soil. They absorb significant amounts of rain and prevent downstream flooding.

Previous studies have shown that when downstream waters receive elevated amounts of nitrogen and phosphorus without the ability to store and transform nutrients, this can result in algal blooms and low oxygen in reservoirs and coastal areas / Photo by: Jon Bilous via 123RF

 

Producing Large Amounts of CO2

The global carbon cycle is immensely complex. It involves every living organism and natural habitat on our planet. Thus, scientists deal with this complexity by describing the carbon cycle by lumping similar objects or environments into simpler groups. Carbon flux refers to the amount of carbon exchanged between the Earth’s carbon pools – ocean, atmosphere, grassland, and forest. 

While streams account for more than a third of the global carbon runoff, the role of mountain streams in global carbon fluxes has not yet been evaluated.

Researchers from Ecole Polytechnique Fédérale de Lausanne’s Stream Biofilm and Ecosystem Research Laboratory (SBER) released the first large-scale study of CO2 emissions of mountain streams and their role in global carbon fluxes. According to Science Daily, an American website that aggregates press releases about science, the researchers gathered large environmental data from the streams draining the world's main mountain ranges.

They specifically focused not only on the streams’ hydrologic and geomorphologic properties but also on their soil organic carbon content within the catchments. After that, the scientists developed a model that estimated the natural CO2 emissions from more than 1.8 million mountain streams across the world.

The global carbon cycle is immensely complex. It involves every living organism and natural habitat on our planet / Photo by: Teeravut Atthasak via 123RF

 

The study published in Nature Geosciences discovered that mountain streams have a higher average CO2 emission rate per square meter compared to lower altitudes. This is because there’s an added turbulence in mountain streams caused by water flowing down the mountain slopes. Thus, they are more likely to account for 10 percent to 30 percent of CO2 emissions despite making up only 5 percent of the global surface area of the fluvial networks. 

Battin stated that the findings of the study open new opportunities to better understand where all that CO2 comes from. At the same time, they can now address how experts can accurately account for the world's alpine regions in the assessments of the global carbon cycle. Considering the fact that carbonate rock dominates geology in several parts of the world, the researchers suggest that the CO2 comes from geological sources.

However, Battin emphasized that there should be long-term monitoring of carbon fluxes in mountain streams to understand how the climate crisis affects their biogeochemistry. "We are just starting to discover the role of mountain streams for the global carbon cycle. These are exciting times for environmental sciences,” he said.

There’s so much to learn and study regarding the global carbon fluxes and how this impacts our planet as a whole. These studies prove that streams are an integral part of our ecosystem, in need of care just like Earth's other natural resources.