Storing carbon in soils — a climate mitigation tool being explored in southeast Wisconsin
Climate change is the biggest environment challenge the world is facing. Efforts are underway to mitigate its impacts.
One effort is piggybacking on restoring natural areas — as ecosystems becomes healthier, the soils can store more carbon. The Nature Conservancy, a global environmental nonprofit, is spearheading the approach at a nature preserve in southeast Wisconsin.
Brian Miner walks through the Newell and Ann Meyer Nature Preserve, located ten miles west of Mukwonago, Wisconsin. He coordinates The Nature Conservancy stewardship projects in southeast Wisconsin.
The preserve is 653 acres — there's an oak savanna, open wetlands, prairies.
There are layers of restoration underway. Take the oak savanna, for example. “We’re right on target for where I expected. The real heavy lifting was getting rid of buckthorn. You couldn’t see from here to the cabin five years ago. It generally takes several years to continue treating that," he says.
Miner says while loads of work lie ahead to control invasive shrubs and plants on the entire parcel, preserving the diverse terrain is also important.
“Here we have some south-facing slopes and north-facing slopes and we have the wetland with a whole bunch of different water levels — so all of that creates little niches of habitat,” Miner says.
The habitat here forms a "resilient connected network" along with land in other preserves and the Kettle Moraine State Forest. The areas will become increasingly important to plants and wildlife in the face of climate change.
“As we restore ecosystems, we’re increasing the local connectivity so that species are able to move across the landscape,” Miner says.
In 2020, The Nature Conservancy embarked on a three-year strategic plan to make sure all of their programs across the world are focusing on dealing with climate change and the biodiversity crisis.
That included more finely-tuning the understanding of benefits of restoration in Miner’s region.
"One of the things that came out of that is thinking about how to understand the way carbon cycles through these particular types of ecosystems and how does this preserve, and other preserves like it, contribute to climate mitigation," Miner says.
The Nature Conservancy teamed up with the Northern Institute of Applied Climate Science, located in Michigan, to puzzle out the answer.
"We asked them to look at the research and help us to understand how management actions can affect the way carbon is stored in the ecosystem," Miner says.
They learned the vast majority of the carbon in this ecosystem is stored underground in the soils.
“So the way it works in these types of ecosystems and really, in general, is the plants through photosynthesis store carbon in their live tissue and then into their root structure underground and over time that’s built up into the soil,” Miner says.
That doesn’t happen overnight. “It take decades, but definitely millennia to build up soil carbon. The good news is once it’s in the soil, the carbon is really stable. Unless the soil is really disturbed, that carbon is locked in there a long time,” Miner says.
That information reinforces The Nature Conservancy’s management technique here — gradually rid the landscape of invasives and encourage native plants to take hold. That process too takes time.
“This probably the most diverse and best restored woodland so far on this property. Some are just chocked full of buckthorn and honeysuckle and other invasive woody species … that are very aggressive and can resprout aggressively. So it takes a long time to reduce that cover. And then we start reintroducing fire and inter-seeding grasses and wildflowers,” Miner says.
Tackling invasives like buckthorn is an intense process.
“[However,] the advantage over time is that the tall grasses and even short grasses like little bluestem, they tend to have much more robust root structures. So a lot more proportionately of the carbon they’re storing is going into the ground, versus buckthorn that has fairly shallow roots and not really storing much into the soil,” he explains.
Miner says research shows the more diverse the ecosystem, the more it can adapt to climate change. “And then in turn that the carbon that’s stored in the ecosystem."
As for how much carbon could the preserve's combined soils could ultimately store, that’s a question Miner can’t answer. “The tools that are available for measuring carbon temporally aren’t at the right scale for management. And when we’re thinking about soil carbon it happens so slowly. So the goal of our work has been less how much carbon can be stored here and more thinking how the carbon is stored and how our action over time can optimize carbon storage."
Recently, the Nature Conservancy held its first workshop to share what it’s learning about carbon storage. Miner says 30 private and public land managers from area municipalities, counties and the state showed up. Miner says they all take the long view of why ecosystem restoration matters.
“And so the goal of the workshop was to help land managers understand how to think about and how to plan for carbon stewardship as one of many multiple objectives that we’re managing for,” Miner ays.
And he says take credit for what you’re already doing.