Before the rush of humanity came to California in search of gold, the San Joaquin Delta was rich in peat soil and much of what is now farmland consisted of wetland and swamps. Mother nature’s own carbon sponge.
Over the past 150 years, levees built to “reclaim” the land for agriculture have allowed much of that rich peat soil to continually degrade, exposing it to wind, rain, and oxygen. Through persistent land alteration and unsustainable agriculture, the carbon has become “liberated” from the soil and much of the land to subside. In other words, a sinking delta consisting of denuded soil.
Some islands farmed in the delta are as much as 20 feet below the surface of the water, kept dry only by the network of levees.
A pilot project funded by the California Department of Water Resources completed in 2005 and a new “carbon farming” project spearheaded by the U.S. Geological Survey set to start next spring may help change both the environmental and climate implications of this soil erosion and subsidence while providing economic opportunity for farmers.
A new crop of carbon in the north forty
The concept is to replant test plots in the delta with cattails and tules, plants that existed when these parts where marsh and wetland. These marsh plants will reproduce, die, and decompose thus helping restore the delta’s peat soils and wetlands. At the same time soaking up carbon.
The pilot program run by the DWR ran from 1997 to 2005 and restored ten inches of peat soil on the sinking, carbon-liberating island of Twitchell in the delta. The project also demonstrated the ability of the process to sequester as much as 25 tons of carbon per acre per year and eliminate the CO2 emissions produced from current farming practices.
That initial promise of that program has led to a $12.3 million dollar, three-year project by the USGS(pdf) and University of California at Davis to test the concept on 400 acres in the delta.
Soil and range management is recognized as a key factor in reducing atmospheric concentrations of CO2, and many governments are catching onto the idea of carbon farming. Many of these “carbon farming” projects refer simply to paying farmers to plant trees and other vegetation that store carbon.
The projects in the California delta entails specifically rebuilding wetlands and is not without risks, as a USGS briefing paper notes:
“Large scale efforts to manage the environment have a decidedly mixed record of success.”
These risks include the release of methane and nitrous oxide from the restored wetland, both more potent than CO2 as greenhouse gases. Another potential problem is that under certain conditions, the sequestered carbon could produce methylmercury, a neurotoxin that accumulates in the food chain and concentrates in fish. Eating those fish can cause serious health problems.
The pilot project by the DWR showed widely varying measurements of methane and scientists hope to gain more insight into these potential hazards with the larger scale project this spring.
Despite the potential problems, there is substantial promise that restoring the delta’s wetlands could accomplish three important goals:
- Sequester Carbon
- Reverse land subsidence
- Provide a livelihood from managing the land in a sustainable manner
Roger Fujii, Bay-Delta program chief for the USGS California Water Science Center summed it up in a statement to the press:
“This project is an investment in California’s future that could reap multiple benefits over several decades – for California, the nation and the world.”