Soils are the Earth’s largest carbon storage depot after oceans and fossil fuels. Yet scientists estimate that since the industrial revolution, agricultural practices have caused massive carbon losses from the soil, contributing up to a third of all the increased CO2 in the global atmosphere.
But there's hope for restoring this great carbon sink. The science and practice of ecological farming now show that farmers can effectively put carbon back into the soil – and that this, in turn, can be a huge help in the battle against climate change.
Earlier this month, The Scientist published an online report that explains just how sustainable agriculture can increase soil carbon. The bottom line: ecosystem management, such as inclusion of diverse crops including legumes, is crucial in determining whether carbon is lost from or accumulates in soil.
It's all about how soil microorganisms & plants interact
If you give them a variety of good, healthy foods, they grow big and strong — it works for kids and so too it works for soils and the millions of critters therein. Microorganisms such as bacteria and fungi in the soil interact in many complicated ways with plants and soil. Those interactions determine if carbon builds up in the soil through accumulation of soil organic matter, or leaves the soil through critter growth and respiration.
And here's even more detail for those like me who find the inner workings of soil fascinating: how it all plays out, the researchers found, is particularly influenced by the role mycorrhizal fungi play in taking up carbon and forming stable soil aggregates that protect that carbon from degradation. This finding about fungi is supported in other studies as well.
The Scientist study authors were particularly interested in how these interactions may change under increasing temperatures and CO2 concentrations of climate change. I'm sure there's a followup study in the works.
Soil-friendly policies needed
Whether we fully understand the underlying mechanisms or not, the literature is replete with examples showing that agroecological practices are good for the environment, help mitigate climate change and offer productive, healthy solutions to destructive chemical-intensive industrial-scale agriculture around the globe.
But to ensure widespread implementation of soil-building, climate-friendly farming practices, we need good policies with government and public support.
In the coming months Congress will negotiate the next Farm Bill. If you'd like to see a version of this law that supports smart farming and healthy soil, visit our partners at the National Campaign for Sustainable Agriculture to see what's at stake and how you can help.