Study shows methane emissions from wetlands increase significantly at high latitudes

Wetlands are Earth’s largest natural source of methane, a powerful greenhouse gas about 30 times more potent than carbon dioxide in warming the atmosphere. A research team from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) analyzed data on methane emissions from wetlands across the boreal-Arctic region and found that these emissions have increased ‘around 9% since 2002.

Livestock and fossil fuel production are well studied for their role in releasing tons of methane per year into the atmosphere. Although more uncertain, quantifying natural emissions from wetlands is important for predicting climate change.

Scientists expect methane emissions from wetlands to increase because temperatures in boreal and Arctic ecosystems are rising at a rate about four times the global average, but it is difficult to say by how much, because Monitoring emissions in these large, often waterlogged environments is very difficult. -until now.

“Boreal and Arctic environments are carbon-rich and vulnerable to warming,” says Qing Zhu, a research scientist at Berkeley Lab and lead author, with Kunxiaojia Yuan, a postdoctoral researcher at Berkeley Lab, of a new study that analyzed the collected data from several advanced monitoring systems. methods to determine the 9% increase in emissions over the past two decades.

An article published in Climate change this week describes their approach.

“Rising temperatures increase microbial activity and vegetation growth,” Zhu continues, “which are associated with emissions of gases like methane. By understanding how natural sources of methane are changing, we can more precisely monitor gases greenhouse gases which inform scientists about the current and future state of climate change.

Higher latitude wetlands: quantifying methane emissions and their evolution

Although methane stays in the atmosphere much shorter than carbon dioxide (10 years versus 300 years), its molecular structure makes it 30 times more capable of warming the atmosphere than CO.₂.

Higher temperatures not only enhance the microbial activity of methane-releasing microbes found in saturated soils, they also increase the area of ​​waterlogged soils where these microorganisms thrive as frozen soils thaw and more precipitation falls as rain rather than snow. . This is why scientists expect methane emissions to increase in these higher latitude regions and why there is an urgent need to quantify methane more precisely.

The most common way to measure greenhouse gas emissions is to trap gases emitted by soils at a fixed location in a chamber, allowing them to accumulate over a defined period of time. Another method, more self-contained turbulent covariance towers several meters high, continuously measure the exchange of greenhouse gases between soils, plants and the atmosphere over large areas of an ecosystem, and often in hard-to-reach places such as wetlands.

The Berkeley Lab research team combined data acquired using both methods to analyze more than 307 total years of methane emissions data from wetlands in the Arctic-Boreal region, creating a better picture factors influencing emissions over hundreds of acres of land and over several minutes or even decades. .

The research team found that between 2002 and 2021, wetlands in these regions released an average of 20 teragrams of methane per year, or as much as the weight of about 55 buildings in the Empire State. They also found that emissions have increased by about 9% since 2002.

Additionally, the researchers examined two “hotspot” areas in the Arctic and boreal regions, which have significantly higher area-based methane emissions than surrounding environments. They found that about half of average annual emissions came from these hotspots, helping to inform and target mitigation efforts and future measures.

Environmental factors affecting emissions from wetlands

The researchers also investigated which environmental factors explained the higher methane emissions, finding two main factors: temperature and plant productivity.

Higher temperatures increase microbial activity; When temperatures rise, whether on average due to climate change or in some years due to climate variability, more methane is released in the process. The team found that temperature was the dominant control of wetland emissions and their variability in boreal-Arctic ecosystems.

This can lead to a climate feedback, where methane emissions from increased microbial activity increase atmospheric temperatures, leading to more methane emissions, and so on.

Higher plant productivity increases the amount of carbon in the soil, which fuels methane-producing microbes. Researchers found that when plants were more productive and active, releasing substrates that help microbes grow, methane emissions from wetlands increased.

The team also identified that the year with the highest methane emissions in wetlands, 2016, was also the warmest year in high latitudes since 1950.

Since methane has a fairly short lifespan in the atmosphere, it can be reduced and eliminated relatively quickly,” says Zhu. “Providing a more precise understanding of the role wetlands play in the global climate system and how and at what rate they emit methane. have increased, this research can provide a scientific basis to help understand and combat climate change.