Soil as Carbon Storehouse: New Weapon in Climate Fight?
The degradation of soils from unsustainable agriculture and other development has released billions of tons of carbon into the atmosphere. But new research shows how effective land restoration could play a major role in sequestering CO2 and slowing climate change.
In the 19th century, as land-hungry pioneers steered their wagon trains westward across the United States, they encountered a vast landscape of towering grasses that nurtured deep, fertile soils.
Today, just three percent of North America’s tallgrass prairie remains. Its disappearance has had a dramatic impact on the landscape and ecology of the U.S., but a key consequence of that transformation has largely been overlooked: a massive loss of soil carbon into the atmosphere. The importance of soil carbon — how it is leached from the earth and how that process can be reversed — is the subject of intensifying scientific investigation, with important implications for the effort to slow the rapid rise of carbon dioxide in the atmosphere.
According to Rattan Lal, director of Ohio State University’s Carbon Management and Sequestration Center, the world’s cultivated soils have lost between 50 and 70 percent of their original carbon stock, much of which has oxidized upon exposure to air to become CO2. Now, armed with rapidly expanding knowledge about carbon sequestration in soils, researchers are studying how land restoration programs in places like the former North American prairie, the North China Plain, and even the parched interior of Australia might help put carbon back into the soil.
Absent carbon and critical microbes, soil becomes mere dirt, a process of deterioration that’s been rampant around the globe. Many scientists say that regenerative agricultural practices can turn back the carbon clock, reducing atmospheric CO2 while also boosting soil productivity and increasing resilience to floods and drought. Such regenerative techniques include planting fields year-round in crops or other cover, and agroforestry that combines crops, trees, and animal husbandry.
Recognition of the vital role played by soil carbon could mark an important if subtle shift in the discussion about global warming, which has been heavily focused on curbing emissions of fossil fuels. But a look at soil brings a sharper focus on potential carbon sinks. Reducing emissions is crucial, but soil carbon sequestration needs to be part of the picture as well, says Lal. The top priorities, he says, are restoring degraded and eroded lands, as well as avoiding deforestation and the farming of peatlands, which are a major reservoir of carbon and are easily decomposed upon drainage and cultivation.
He adds that bringing carbon back into soils has to be done not only to offset fossil fuels, but also to feed our growing global population. "We cannot feed people if soil is degraded," he says.
One implication of this research, says Goreau, is that "the effect of most landscape alterations is to convert them from systems that store carbon efficiently ... toward ones that are inefficient in the use of nitrogen, and as a result are losing carbon storage." By landscape alterations, he means from forest to cropland, or from small farms to industrial agriculture operations that use the chemicals that inhibit the mycorrhizal and microbial interactions that store carbon.
Says Rattan Lal: "Soils of the world must be part of any agenda to address climate change, as well as food and water security. I think there is now a general awareness of soil carbon, an awareness that soil isn’t just a medium for plant growth."
POSTED ON 04 Mar 2014 IN Business & Innovation Climate Science & Technology Science & Technology Sustainability Water North America
Read the complete article on Yale Environment 360 http://e360.yale.edu/feature/soil_as_carbon_storehouse_new_weapon_in_climate_fight/2744/