Drying lake beds are a major source of harmful emissions

New research from the Royal Ontario Museum (ROM) highlights a significant, yet previously overlooked source of greenhouse gas emissions: drying lake beds, specifically Utah’s Great Salt Lake. 

Drying lake beds and climate change 

The study, published in the journal One Earth, reports that in 2020, the desiccated bed of Great Salt Lake released 4.1 million tons of carbon dioxide and other greenhouse gases. 

This finding underscores the potential for drying lake beds to become substantial contributors to climate change, exacerbated by global warming.

“Human-caused desiccation of Great Salt Lake is exposing huge areas of lake bed and releasing massive quantities of greenhouse gasses into the atmosphere,” said Soren Brothers, the study’s lead researcher and ROM’s Allan and Helaine Shiff Curator of Climate Change. 

Addressing all activities contributing to emissions

Brothers noted that the significance of lake desiccation as a driver of climate change needs to be addressed in greater detail and considered in climate change mitigation and watershed planning.

According to the study authors, it is crucial that all activities contributing to GHG emissions be fully accounted for as societies adopt strategies to reduce greenhouse gas (GHG) emissions to halt the progress of climate change.

“Inland waters are a critical component of the global carbon cycle, emitting large quantities of carbon dioxide (CO2) and methane (CH4) to the atmosphere and annually burying a similar quantity of organic carbon as is buried in oceans,” the researchers added.

Fluctuating levels of saline lakes

Great Salt Lake’s water levels vary yearly, mainly depending on the volume of meltwater from surrounding mountains. However, human activities like agriculture, industry, and municipal water use have significantly depleted the lake over the years. 

Globally, similar patterns are observed in other iconic saline lakes such as the Aral Sea, Lake Urmia, and the Caspian Sea. 

The drying of these lakes not only destroys critical habitats and degrades air quality but also accelerates climate change by emitting greenhouse gases like carbon dioxide and methane from exposed sediments.

Emissions from drying lake beds

The research team measured carbon dioxide and methane emissions from the exposed sediments of Great Salt Lake between April and November 2020. 

These measurements were compared with estimates of aquatic emissions to determine the anthropogenic greenhouse gas emissions associated with the lake’s desiccation. 

The findings indicated that the lake bed emitted 4.1 million tons of greenhouse gases, primarily carbon dioxide (94%), accounting for approximately a 7% increase in Utah’s human-caused greenhouse gas emissions for that year.

Measuring emissions in Great Salt Lake

Fieldwork was conducted while Soren Brothers was an assistant professor of limnology at Utah State University (USU). The lead author, Melissa Cobo, was a master’s student at USU, and co-author Tobias Goldhammer is a researcher at the Leibniz Institute for Freshwater Research (IGB Institute) in Berlin, Germany. 

The team measured greenhouse gas emissions every two weeks using a portable analyzer attached to a closed chamber. They visited seven sites at the south end of the lake and sampled three additional locations during an intensive three-day campaign to determine spatial variability. 

As methane is 28 times more potent as a greenhouse gas than carbon dioxide, the global warming impact was calculated in “carbon dioxide equivalents” to reflect methane’s greater impact.

The data showed that greenhouse gas emissions from the dried lake bed were strongly related to warm temperatures, even at sites exposed for over two decades. 

A new driver of atmospheric warming 

To assess whether the lake had historically been a significant greenhouse gas source, the team also measured near-shore emissions and analyzed water chemistry. 

The results indicated that the lake itself was not likely a significant greenhouse gas emitter, making the current emissions from the dried bed a novel driver of atmospheric warming.

As climate change exacerbates drought conditions in arid regions, the desiccation of rivers and lakes could contribute to feedback loops that accelerate climate change. This underscores the need for these emissions to be considered in global greenhouse gas output assessments and in the development of reduction policies.

Broader implications of the study 

The implications of this study are broad and significant. If similar greenhouse gas emissions are occurring from other drying lakes around the world, the cumulative effect on global greenhouse gas levels could be substantial. 

The research highlights the need for more comprehensive monitoring and mitigation strategies for drying lakes as part of global efforts to combat climate change.

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