Improving our landscape and land management practices to protect against climate change impacts requires an exhaustive list of ingredients: partnerships, dollars, public policy and landowner willingness.
The one thing connecting all those needs is sound data.
The U.S. Department of Agriculture (USDA) launched a research effort in 2021 to study how ecosystems restored under the Conservation Reserve Program (CRP) contribute to climate mitigation by measuring and modeling soil and vegetation carbon stocks and greenhouse gas fluxes. Ducks Unlimited is leading a multi-institution effort focused on wetlands that will conclude in 2026.
Restored wetlands are increasingly being studied as a natural solution for climate change mitigation and adaptation. This study, funded by a $3.2 million USDA grant, aims to quantify that solution. “There’s a big impetus to better document the lifecycle of a wetland and how that contributes to climate mitigation and climate adaptation,” said Ellen Herbert, Ph.D., Ducks Unlimited senior scientist.
Researchers will spend the next few years coring holes in wetlands at hundreds of sites across the Midwest and Great Plains to monitor soil health and carbon. Partners include the U.S. Geological Survey, University of Missouri, University of Texas, Kenyon College, Clemson University, United Tribes Technical College, Pennsylvania State University, USDA Agricultural Research Service and Farm Service Agency.
The Need
On a global scale, wetland drainage alters greenhouse gas cycles and associated climatic conditions. While only covering 4% to 6% of the earth’s land area, wetlands account for 20% to 30% of total terrestrial carbon storage in soils. However, wetlands are also responsible for 30% of global methane emissions.1 The relationship between storing carbon and releasing methane has not been studied fully and recent research2–4 indicates it depends in part on surrounding land use, wetland hydrology and wetland size.
Across the agricultural U.S. Midwest and Great Plains, 40% to 90% of historic wetlands have been drained for agricultural production since 1780.5,6 This is also the region where more than 80% of the wetland restorations through CRP are delivered.
CRP was first signed into law in 1985. The voluntary program contracts with agricultural producers so that environmentally sensitive agricultural land is not farmed or ranched but is instead devoted to conservation benefits. CRP protects more than 20 million acres (8.1 million ha) of American topsoil from erosion and is designed to safeguard the nation’s natural resources.
Despite restored wetlands’ ability to sequester soil organic carbon approximately five times faster7 than restored grasslands, there has been relatively little focus on the climate benefits of restoration of the millions of drained wetlands embedded in the agricultural landscapes of the U.S.
The study team will measure and model the potential for climate mitigation through wetland restoration under CRP.
The Method
This first step in developing reliable soil organic carbon rates and greenhouse gas emission estimates based on robust models is high quality, high quantity and targeted observations, which are currently unavailable for restored wetlands, including the CRP.
The five-year program is now in its second field season of collecting data. Field crews are descending on more than 80 CRP wetland restoration sites across 15 states to take core samples, vegetation samples and record site descriptors (Figures 1–4). Greenhouse gas sampling will occur three times through the course of the growing season within multiple chambers along transects at each site. Researchers will develop geospatial datasets of key drivers of carbon cycling including biomass, nutrient loading and surrounding land use. The data will then be calibrated to model the wetlands, concentrating on the soil carbon stocks and rates of soil carbon accumulation and the flux rates of greenhouse gasses including carbon dioxide, methane and nitrous oxide. Additional data on flooding and wetland vegetation that will help scale data beyond sampling sites though empirical and process-based models.
“We will model scenarios that account for changes in soil carbon concentration and mass and greenhouse gas emissions that take place when wetlands are drained and cropped or restored, and also examine how surrounding land use, in particular perennial cover versus row-crop agriculture, impacts climate change factors,” Herbert said.
What’s Next?
The goal is to quantify the impact of restored wetlands on soil carbon accumulation, soil carbon storage, greenhouse gas emissions (methane and nitrous oxide) in addition to drivers of carbon cycling like hydroperiod, biomass and surrounding land use. This data may be used to evaluate restoration success, provide recommendations on improving wetland restoration outcomes and communicate benefits of wetland restoration programs like CRP.
“CRP is economically important to producers and provides recreational opportunities, but we’re looking at it for broader societal impacts,” Herbert said.
Beyond educating policymakers, municipal leaders and private sector organizations, the study will provide answers to landowners cooperating in the CRP. The study will enable CRP enrollees to know what their participation is achieving and will help the USDA promote the program.
Ducks Unlimited Canada is involved in a similar study that will offer similar data across a broader landscape. Both projects will guide landscape conservation on a national scale.
Finally, the study creates a foundation to develop future conservation and carbon cycling experts by offering valuable learning opportunities for the undergraduate and graduate students conducting research. Herbert explained, “It’s a unique experience, as these students get to interface with the farmers and producers on the ground, offering a realistic view of science and what conservation really involves.”
References
- Mitsch WJ, Gosselink, JG. Wetlands, 5th ed. Hoboken, Wiley. 2015.
- Bansal S. et al. Large increases in methane emissions expected from North America’s largest wetland complex. Science. Adv. 9, eade1112(2023).DOI:10.1126/sciadv.ade1112.
- Tangen BA, Bansal S. Prairie wetlands as sources or sinks of nitrous oxide: effects of land use and hydrology. Agricultural and Forest Meteorology, 2022.
- Bansal S, Tangen BA, Gleason RA, et al. Land management strategies influence soil organic carbon stocks of prairie potholes of North America Wetland Carbon and Environmental Management, 2021.
- Dahl TE. Wetlands Losses in the United States 1780s to 1980s. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C. 1990. P. 13.
- Dahl TE. Status and trends of prairie wetlands in the United States 1997 to 2009. U.S. Department of the Interior; Fish and Wildlife Service, Ecological Services, Washington, D.C. 2014.
- Euliss Jr. NH, Gleason RA, Olness A, et al. North American prairie wetlands are important nonforested land-based carbon storage sites. Sci. Total Environ. 2006.361: 179–188.
About the Experts
Chris Sebastian is the communications director at Ducks Unlimited. He leads a national team responsible for educating stakeholders about the multitude of benefits wetlands conservation provides for people and wildlife.
Ellen Herbert, Ph.D. is a senior scientist at Ducks Unlimited’s National Headquarters. Herbert works with cross-disciplinary teams of biologists, hydrologists, engineers, and ecologists to evaluate the outcomes of habitat restoration and conservation work across the continent.
