11 July, 2018
Forests: The greenest pastures?
Ethiopia - How can you keep farms productive for generations while reducing the impact on the environment? In sub-Saharan Africa, the answer might be forests - and cow poo.
Agricultural intensification - producing more food on less land - has relieved the hunger of millions, through a combination of improved crop variety, fertilizers and irrigation. This "Green Revolution" has improved food security in many countries, but it has also had unforeseen environmental and social consequences. Farming the same land over and over can deplete the nutrients in the soil, and to restore them, the conventional approach has relied on chemical fertilizers and fossil-fuel guzzling machinery to distribute them.
‘Sustainable agricultural intensification' seeks to find another way, and a new study has found promising evidence that retaining forests in agricultural landscapes can have a dramatic effect on the productivity, resilience, sustainability and social equality of nearby farms.
The secret to it all is livestock, says lead author Jean-Yves Duriaux Chavarría, from the International Maize and Wheat Improvement Center (CIMMYT) - and the strength of the results surprised even the researchers, he says.
"We never expected there would be so many positive implications of grazing your cattle in the forests."
Duriaux Chavarría and colleagues studied a landscape in southern Ethiopia, bordering the state-owned forest of Munesa. "Imagine a savannah kind of landscape with acacia trees - but instead of grass you have wheat, and then on the horizon you have a mountain with a forest, very green and lush."
Duriaux Chavarría spent several weeks riding around the area on a motorbike, trying to identify a site that would provide grounds for the perfect ‘natural experiment' that he and co-author Frédéric Baudron, also of CIMMYT, had in mind: a gradient of zones that were otherwise similar but differed in their distance from the forest. One was right on the border, one 5.5 kilometers away, and one 11 kilometers away, near a major town.
"Our hypothesis was that the more intensive or simplified landscapes, closer to markets, would be more productive than the more ‘nature-friendly' ones near the forest," says Duriaux Chavarría.
That wasn't the case. In fact, all three sites were practically indistinguishable in terms of total farm productivity - the amount of food energy the landscape produced. The villages near the forest had much higher livestock productivity, without compromising on crop productivity, either.
CASCADE OF EFFECTS
Critically, farmers living near the forest could keep more cows and goats, and send them among the trees to graze.
"You don't have saving accounts, but having livestock gives you options. You can sell a cow or a couple of goats, or some fuel wood, and then you have some extra cash when you need it. The forest is there to provide when you have a critical time or need to invest in your farm," says Duriaux Chavarría.
Social inequality was therefore much higher in the villages farthest from the forest. In the distant zone, 33 percent of farming households did not own livestock - that fell to 18 percent in the intermediate zone and 6 percent in the near zone. "Where there was less access to forest, with no safety nets, poorer farmers were a lot worse off."
The animals also brought part of the forest home with them.
"Livestock are key distributor of nutrients from forest to farm. They spend 10 to 12 hours in the forest, and then at the end of the day, they walk back and poo on the farm. We estimated that about half of what they eat comes back to the farm. They're big animals, they eat a lot, they poo a lot - so that's a lot of nutrients."
That meant that those living near the forest were better off in terms of nutrition, something the authors have explored in another paper led by Baudron. Farmers could use the manure as fertilizer for crops, and could grow enset, or ‘false banana' - a tall root crop that's an important staple in southern Ethiopia - and in its shade grow other vegetables.
"And all this is because the forest gave you feed to have livestock, which came and pooed on your farm. We never expected to have such a cascade of effects," says Duriaux Chavarría.
The paper supports a growing evidence base that forests and trees contribute to agricultural production in numerous ways, says co-author Terry Sunderland, from the Center for International Forestry Research(CIFOR) and the University of British Columbia.
"The pathways of these contributions often have to be teased out as they are not always immediately obvious," says Sunderland. "The contribution of this paper to this body of evidence suggests that myriad ecosystem services play an integral role to livestock husbandry by providing nutrients and reducing the need for external inputs - critical issues for resource-poor farmers."