A Look at Rangeland Soil Carbon Loss and How Envu Is Taking Action

A new study published in Communications Earth & Environment, a Nature Portfolio journal, highlights the significant loss of soil carbon due to the conversion of native perennial shrublands to invasive annual grasslands. The research is the first to comprehensively quantify the impact of annual grass invasion on soil carbon stocks, a problem with implications extending far beyond the western United States.

The publication, titled "Annual grass invasions and wildfire deplete ecosystem carbon storage by >50% to resistant base levels," is the result of a two-year research collaboration between scientists from the United States Geological Survey (USGS) and Envu. While the study focuses on the sagebrush steppe in the western U.S., the findings can be applied to similar ecosystems worldwide facing similar threats from invasive species.

A Deeper Look at Soil Carbon Loss in Rangelands

The research process involved USGS scientists collecting and analyzing over 1,000 soil samples from three locations in the sagebrush steppe, a vast ecosystem that spans much of the western U.S. The researchers sampled soil cores down to a full meter, a key difference from previous studies that often sampled down to 30 centimeters or less. This deeper sampling allowed them to capture a more complete picture of soil carbon storage and the impacts of grass invasion. 

While the scientific community has long understood the ecological issues associated with these invasive species, the magnitude of their impact on soil carbon was largely unknown. Now, the data has revealed that the conversion of native perennial shrublands to invasive annual grasses, such as cheatgrass, can lead to a 42% to 49% reduction in soil carbon.

“This research shows that a disturbance such as annual grass invasion can quite rapidly deplete soil carbon that may have built up over thousands of years,” said Dr. Harry Quicke, Envu North America solutions development lead and one of the paper’s authors. Quicke also noted that vast areas of native shrublands have already succumbed to grass invasion and, without intervention, this process will continue at an alarming rate. “The scale of this problem is immense; over 50 million hectares (123 million acres) have already been impacted by invasive grasses, and an additional 363,000 hectares (897,000 acres) are converting each year.”

The loss of soil carbon from these lands represents a significant release of carbon dioxide into the atmosphere. The rapid rate at which invasive grasses are converting native shrublands underscores the urgency for action to mitigate the loss of soil carbon and biodiversity. 

Research Implications for Land Managers

The study’s findings are particularly relevant to private land managers and government agencies that manage public lands. On a per-unit basis, the data shows a loss of 187 metric tons of carbon dioxide equivalent (CO2eq) per hectare, or 75 metric tons of CO2eq per acre. This highlights the urgent need to stop the ongoing conversion of deep-rooted, diverse, native perennial systems to shallow-rooted exotic annual grass-dominated systems.

“There is broad interest in carbon sequestration, and many people think that carbon in the soil is secure,” explained Dr. Matthew Germino, a USGS research ecologist and the principal investigator of the study. “We now have a robust finding that carbon in rangeland soils is not so secure and is vulnerable to one of the most extensive and intensive forms of land degradation — the cheatgrass-fire cycle.” 

This cycle describes a recurring pattern where the invasive annual grass, such as cheatgrass, grows rapidly in late winter and early spring and produces abundant dry fuel, leading to more frequent and intense wildfires. After each fire, cheatgrass often reestablishes quickly, outcompeting native vegetation and perpetuating a cycle of ecosystem degradation.

The researchers also determined that the impact on soil carbon is similar whether land is burned by wildfire or invaded by exotic annual grasses. This was an unexpected finding as the prevailing wisdom held that wildfire would have a far greater impact.

How Envu Is Taking Action

This research provides more compelling evidence for the importance of the commitment to nature-positive innovation from Envu, the first of five key pillars in the company’s sustainability strategy. Nature-positive innovation encompasses how Envu is enhancing biodiversity and helping the ecosystem flourish by:

• Controlling invasive species and pests.
• Protecting and restoring native forests and rangelands.
• Using digital technologies to optimize management strategies.

The new data reinforces the need for innovative solutions that promote sustainable land management practices. One way Envu is doing this is by controlling invasive species with highly effective, targeted solutions. As noted in the 2023 Envu Sustainability Report, Envu products actively contribute to controlling more than 11% of the species in the Global Invasive Species Database and 17% of the top 100 most impactful invasive species. 

Specifically, Envu is working to eliminate invasive plant species like cheatgrass with innovative products like Rejuvra^® herbicide and the RangeView™ digital platform in the U.S., which helps land managers and ranchers identify and map invasive species in rangeland so they can take action. By providing vegetation managers with these tools, Envu is helping them control germinating annual grasses, allowing perennial native plants to recover, increasing biodiversity and improving habitats.

“We’ve long been aware that there are a number of benefits to controlling invasive grasses, including increasing forage production for livestock, improving habitat for pollinators and wildlife, and reducing wildfire risk,” said Quicke. “Now we know that preventing the spread of invasive grasses can also avoid soil carbon losses.”

The insights gained from the new data can be used to inform land management practices and policies in other regions and countries grappling with invasive species. By sharing the findings of this research with the wider community and continuing its research collaboration with USGS, Envu aims to raise awareness and promote the adoption of effective strategies for mitigating the global impact of invasive species on soil carbon and climate change. 

Phase 2 of the research collaboration with USGS is already underway, expanding the study to encompass a broader geographic range. For more information on the research and its implications, you can visit this page on USGS.gov.