Q: Can ecological restoration like TWI’s projects help address climate change?
There’s a lot about climate change and carbon dioxide in the news lately. Among scientists, there is general consensus that the climate is changing because of an increase in atmospheric carbon from a variety of sources. At the Wetlands Initiative (TWI), we look to ecological restoration as part of the solution to this problem. Projects like those undertaken by TWI aim to return habitats to healthy conditions so that naturally occurring ecosystem services like carbon sequestration can take place.
TWI and other scientists hypothesize that restoring prairie ecosystems on a large scale can be one method for helping to reduce the amount of carbon in the atmosphere. However, there is yet little quantitative data on how much carbon can be sequestered by restored prairie—relative to native prairie—or how fast carbon accumulates as the restoration matures.
The Wetlands Initiative has grabbed the opportunity to increase scientific knowledge in this area during restoration of the recently acquired Sandy Hollow tract at our Sue and Wes Dixon Waterfowl Refuge at Hennepin & Hopper Lakes in north-central Illinois. This 283-acre parcel had been mostly corn and soybean fields for decades—a textbook example of disturbed soils with reduced capacity to store carbon. Intensive restoration by TWI will return the land to a prairie, savanna, and woodland system, providing the perfect opportunity for a “before and after” experiment to measure how much carbon sequestration increases as restoration progresses.
To determine the full potential of restoration and how it may influence carbon levels in the atmosphere, it is crucial to understand concepts like carbon sequestration. Carbon sequestration is the process by which atmospheric carbon dioxide is converted to a form that does not contribute to climate change, and then stored long-term in places like soils, plants, and oceans. Plants and soils—central to TWI’s restoration projects—are natural experts at sequestering carbon. Through the process of photosynthesis, plants draw carbon dioxide out of the air and form carbon compounds that are stored in plant matter. Much of this carbon is slowly returned to the environment as leaves and other parts of the plant are shed, lost, or eaten; dead plant material is eventually broken down by other organisms, decaying to enrich the soil. Over time, soils are able to store incredibly large amounts of carbon, so much that they’re known as a “carbon sink”—that is, more carbon is absorbed than released.
If these soils are disturbed through agriculture or other processes, however, their stored carbon can be released and reenter the atmosphere as carbon dioxide. Over a third of the carbon added to the atmosphere since the 1800s has come from activities like deforestation and exposing the rich carbon deposits contained in topsoil.
Grassland or prairie ecosystems—once dominant in Illinois—are particularly good carbon sinks, largely because the root structure of prairie plants and grasses can reach soil depths of 15 feet or more. With up to 10 times as much biomass occurring below ground as above, there is potentially an immense amount of carbon being sequestered. But with almost all the region’s original prairie now degraded or destroyed, the land’s natural capacity to store carbon has also been lost. TWI’s Sandy Hollow project will be critical in determining if this storage capacity can return to the landscape once restored.
For the research at Sandy Hollow, TWI has partnered with the National Great Rivers Research & Education Center (NGRREC), based outside St. Louis. Over the course of the five-year project, TWI will measure how soil carbon levels change at Sandy Hollow in response to the developing native plant communities. Soil samples taken down to a depth of 1.5 meters were collected for baseline data in 2016, and more samples will be collected over the next five years. The data will demonstrate how carbon stores develop in a landscape that has been converted from farmland back to prairie.
Another component of the TWI–NGRREC research project will measure nutrient levels at Sandy Hollow as the tract is restored, as well as in the adjacent Dore Seep, an ecologically sensitive area of the Refuge. Fertilizer-derived nutrients had been draining downslope into the seep for years from the farm fields at Sandy Hollow, affecting the health of this rare wetland habitat. As Sandy Hollow is restored from farmland back to natural conditions, the nutrient levels should decrease over time and the quality of the groundwater will improve. The changing nutrient levels will be measured through groundwater monitoring wells installed specifically for the project.
Research conducted by TWI with partners such as NGRREC advances our understanding of how restored natural systems can help buffer the effects of climate change and other environmental problems through improved ecological functioning, including increased carbon sequestration and nutrient processing. Such projects yield hard data on just how effectively restored ecosystems provide critical services, and they’re also models for the broader conservation community leading to better restoration in the future.
Iowa: The Power of Prairies
Farming and Carbon Sequestration
The Carbon-Sequestering Power of Soils
Gary Sullivan, Ph.D., is the Wetlands Initiative’s Senior Restoration Ecologist. He has primary responsibility for designing and implementing TWI’s many ecosystem restoration projects, from the Dixon Waterfowl Refuge at Hennepin & Hopper Lakes to Midewin National Tallgrass Prairie and the Calumet region’s Indian Ridge Marsh. These projects, along with his extensive field experiments and research publications, focus on large-scale landscape restoration that incorporates a complex mosaic of habitat, hydrology, and wetland and upland plant communities to promote ecosystem integrity, biological diversity, and high-quality wildlife habitat.