Soil Carbon Challenges

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Issue 286
September/October 2014
Politics of Peace

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Soil Carbon Challenges
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Cover: Navigation by Susanna Bauer. Photo © Simon Cook

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Eco-restoration in the Sierra Gorda Biosphere Reserve, Mexico.

In the rugged mountains of Mexico’s Sierra Gorda, the ugly scars of deforestation mark the steep slopes, which long ago lost their protective forest cover, resulting in deeply eroded soil with a diminished capacity to store water. This led to a huge decline in farm productivity, as the environmental capital of the Sierra Gorda slipped away with every mudslide.

Without carbon, which is present as organic matter, the soil loses its ability to capture and retain water, so the damaging effects of droughts are accentuated. Looking for solutions to these soil carbon challenges, Grupo Ecológico Sierra Gorda (GESGIAP) was formed by residents of the local area, where 30% of the land is still community-owned.

With its partner organisation Bosque Sustentable, GESGIAP adapted the Keyline hydrological design principles originally developed in Australia, which enable rapid and effective soil restoration. The natural contour lines leading from the upper slopes down through the valleys have been enhanced to create ‘infiltration canals’, ensuring that water slowly filters through the soil rather than running off as a flash flood. This improved water retention within the soil helps maintain moisture content in the humus, resulting in increased fertility and microbial activity, and effective capture and storage of atmospheric carbon.

Another activity that is promoted is the local production of fermented bio-fertilisers that use natural ingredients such as crushed volcanic rock, minerals and local microorganisms. The fertiliser is cheap to produce and provides the essential elements of soil regeneration. Jacinto Vigil, a tomato grower from the Sierra Gorda, commented: “We now grow tomatoes at a lower cost that are healthy, chemical-free and of great quality.”

Legumes are renowned for their ability to fix nitrogen in the soil and are now used in the Sierra Gorda as a green manure, thereby increasing biomass and organic matter in these formerly degraded agricultural lands. When ploughed back into the soil, green manures create a sponge-like mass that holds water. It seems miraculous, but with only 1% increase in organic matter, the soil can capture an additional 144,000 litres of water and 132 tonnes of carbon per hectare. In just two years it is possible to reach 82% water absorption capacity, and this in turn directly recharges aquifers, as well as reducing erosion by 68%.

GESGIAP has been also been working with livestock farmers because, managed correctly, cows can help improve the health of soils and increase their capacity to capture carbon dioxide. Currently there are 13 pilot ranches using holistic livestock management techniques such as rotational grazing and low-density stocking. “Cows are an excellent ally to restore life and productivity to the soils,” says Mario Pedraza Ruíz, Director of Bosque Sustentable’s soil conservation programme. Mario’s ranch is part of GESGIAP’s ‘Soil Carbon Challenge’ programme. During the devastating droughts of 2010 and 2012, farmers throughout the region lost many cattle, but Mario’s soil husbandry enabled him to survive without losses.

Improved pasture, independence from agrochemicals and their high costs, healthier animals, and soils with plenty of stored water and carbon are now a reality in Sierra Gorda. “We work from the bottom up and are confident that our model is an effective response to the effects of climate change,” says Mario.

Esther Díaz Pérez is an environmental editor at Reforma journal, Mexico. She regularly travels through Mexico to learn more about nature and conservation issues in the country. She was born in Madrid, Spain.

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