Nature was described as a forgotten solution over and over at last week’s Global Climate Action Summit in San Francisco, from scientists and world leaders to “Han Solo” himself. California’s newly signed Senate Bill 100 requires the state to pull more greenhouse gases out of the atmosphere than it puts in by 2046 using natural and working lands, as well as new technologies.
Natural climate solutions—like finding ways to store carbon in forests, farmlands, grasslands and coastal ecosystems—could account for as much as one-third of the climate mitigation we need between now and 2030 to stabilize warming to below 2 degrees Celsius.
Just for starters, here are four promising natural solutions UC Davis scientists have been researching with their colleagues and partnering organizations:
California’s Healthy Soils Initiative is working with farmers and land managers to encourage practices that build soil organic matter, which helps sequester carbon in the ground and reduce greenhouse gas emissions. Kate Scow, a UC Davis soil science professor, microbial ecologist, and director of the Russell Ranch Sustainable Agriculture Facility, has been looking at how improving soils can store carbon.
She notes that a recent analysis from Russell Ranch measured soil carbon down to about 6.5 feet, roughly six times deeper than most studies. It found that after 20 years, soil carbon mass increased by 12 percent in row crops with compost and cover crops added, compared to systems without those additions. Carbon also increased deeper in the soil, where it is more likely to be protected. Adding cover crops alone increased soil carbon by 3.5 percent, primarily in the surface layer.
Previous studies have found that soil can potentially store between 1.5 to 5.5 billion tons of carbon a year globally. That’s equivalent to between 5 and 20 billion tons of carbon dioxide.
Such results point to healthy soils as being one of many solutions needed to reduce global greenhouse gas emissions.
Trees are very good at storing carbon, but when wildfire burns through forests—as California and the western U.S. is experiencing at an increasing rate—all of that stored carbon literally goes up in smoke.
A study from UC Davis postdoctoral scholar Pawlok Dass and professor Benjamin Houlton found that in California’s current and future climate, grasslands are expected to store more carbon than forests because they are impacted less by droughts and wildfires.
The study does not suggest that grasslands should replace forests on the landscape or diminish the many other benefits of trees. But from a cap-and-trade, carbon-offset perspective, it indicates that conserving grasslands and promoting rangeland practices that promote reliable rates of carbon sequestration could help more readily meet the state’s emission-reduction goals.
A different kind of grass—seagrass—is showing some limited potential for buffering the effects of ocean acidification. A study led by the Carnegie Institution for Science with scientists from the UC Davis Bodega Marine Laboratory found that seagrass meadows’ ability to take up carbon dioxide from the water could turn back the clock on ocean acidification within the meadows by a few decades.
That’s a small offset to the more than 150 years of acidification, but it could help buffer the effects for natural and farmed shellfish. Some shellfish are finding it difficult to form their shells due to the ocean’s increased absorption of carbon dioxide.
Seagrasses also provide an important source of food and habitat for marine animals, help fight erosion, and filter pathogens from the water, making their conservation a “win” on many levels.
Planting fish to reduce methane in rice fields
Fish raised in flooded rice fields during the off season have been shown to grow fatter than those raised in rivers. But the fish may be doing the rice fields a favor in return.
A project is underway in California’s Yuba County to test whether growing fish in flooded rice fields can reduce methane emissions produced by rice cultivation, as previous work in lakes in Finland suggests.
Methane is the second most abundant greenhouse gas and is roughly 25 times more potent than carbon dioxide. Methane released from global rice production makes up about 10 percent of methane in the atmosphere.
The project is based on the premise that the presence of small fish in rice fields allows methane oxidation to occur and bacteria to eat the methane, reducing the amount of greenhouse gases released from the rice fields. It was launched by nonprofit Resource Renewal Institute in collaboration with University of Montana biologist Shawn Devlin and UC Davis fish ecologist Andrew Rypel, with assistance from California Trout.