fevereiro 16, 2006

Sustainable agriculture delivers the crops

In what is possibly the largest-ever analysis of sustainable agriculture practices in developing countries, scientists working in Bangkok, Beijing, Mexico, Sri Lanka, and the U.K. conclude that these techniques improve farmers’ lives by increasing crop yields and preserving the local environment. According to a paper published in this issue of ES&T (pp 1114–1119), poor farmers increased their crop yields by an average of 79% by using techniques such as crop rotation, organic farming, and genetically modified seeds.

Sustainable agriculture practices used by the poor, like this vegetable farmer in southwestern Cambodia, can increase yields by 71%, new research shows.“It’s an exciting report,” Dennis Keeney, emeritus professor at Iowa State University and founding director of the Leopold Center for Sustainable Agriculture, tells ES&T, especially the tables that summarize data from all 57 countries. “You can go right to it and get information without having to run all over the world,” he adds.

Corresponding author Jules Pretty in the department of biological sciences at the University of Essex (U.K.) and his colleagues examined 286 completed and ongoing farming projects in 57 countries. Using questionnaires and published reports, they analyzed 218 projects and then revisited 68 of them 4 years later. The farmers have improved their crop productivity since the early 1990s, and they have reduced pesticide use and increased the efficiency of water use and carbon sequestration. “Whilst it is uncertain whether these approaches can meet future food needs, there are grounds for cautious optimism, particularly as poor farm households benefit more from their adoption,” the authors write.

Beyond providing worldwide data on sustainable agriculture, the paper supports the notion that the international community is failing to improve the lives of poor farmers or to preserve the environment they depend on, Pretty says. A new study from the World Health Organization (WHO) finds that 60% of the benefits derived from healthy natural resources, such as clean water and air, and a relatively stable climate are being lost because of unsustainable land practices.

Despite current technologies, nearly 800 million people worldwide are short of food, and agriculturally driven environmental damage is prevalent, the paper notes. David Pimentel, professor of ecology and agriculture sciences at Cornell University, says this number may underestimate the issue. He notes that the WHO reports that 3.7 billion people are malnourished in the world, the largest number ever in history. Many of these 3.7 billion have food but lack nutrients, such as iron, that are vital for healthy development, Pimentel says.

Pimentel says the paper also brings attention to the fact that we are running out of land to grow food for everyone on the planet. For example, about 10 million hectares of cropland are abandoned every year because of soil erosion, he says. Wood-fuel shortages force farmers to burn crop residues; this in turn removes nutrients from the soil. Farmers could supplement this soil with expensive chemical additions, but most can’t afford to, he adds.

The paper notes that all crops studied needed less water than those grown by less-sustainable methods, with rain-fed crops using the least. The analysis of pesticide-use practices showed that of projects that provided data, 77% had a decline in pesticide application by 71%, while crop yields grew by 42%.

Potential carbon sequestration amounted to an average of 0.35 metric tons of carbon per hectare per year (t-C/ha/yr). But when projected into the future, the researchers found that global carbon sequestration could be 0.1 gigatons C/yr if only a quarter of the total area in each farm studied adopted sustainable practices. The farmers studied increased aboveground carbon sinks on their land by improving their soil’s organic matter.

Researchers like Pretty, Pimentel, and Keeney have written books and papers showing farmers how to work and protect the land, but governments and funding institutions haven’t embraced sustainable farming, they say. Indeed, funds from industrialized countries to poor ones for agriculture development of any kind have dropped significantly since the 1990s until today, according to a working paper from the U.K. Department for International Development. “Most of the programs we are talking about [in our research] happened despite the policy, instead of there being one,” Pretty says. Apart from a worldwide agreement in 1992 to reduce poverty, Pretty says, only 3 countries have policies to help the poor that are focused on food production: Cuba, Switzerland, and Bhutan. “We’ve got the information,” Pimentel says. “We’ve just got to get it to the poor people.” —CATHERINE M. COONEY

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