Planting fertiliser trees alongside maize raises yields and helps the soil absorb carbon from the atmosphere

World Agroforestry Centre

Soil science and agroforestry can help tackle climate change and boost crop yields, say M. S. Swaminathan and Dennis Garrity.

In Zambia's Central Province, a dirt track marks a line between hope and despair. On one side is farmer Collens Mwinga's lush maize crop, a full three metres high, swaying in the breeze.

On the other, a neighbour's maize is withered, barely reaching knee height. Mwinga harvests eight tonnes of maize per hectare — his neighbour is lucky if he gets one tonne.

What does this mean? First, Mwinga can afford to send his ten children to school and give his family a nutritious diet. A strong crop has lifted the Mwingas out of poverty.

A second impact is less visible but important for all of us. Mwinga planted nitrogen-fixing, or 'fertiliser', trees that convert atmospheric nitrogen into soil nutrients. In addition to lowering production costs and raising yields, the trees have improved his soil and helped it absorb carbon from the atmosphere.

In contrast, his neighbour's soil is completely degraded and has released carbon, contributing to global warming.

The story of Mwinga, and thousands of other smallholder farmers around the world has come to be known as 'evergreen agriculture'. It means using scientific knowledge to improve soils as part of the solution to tackling climate change — and is a growing force in many countries.

For that to happen, negotiators at the UN Climate Change Conference in Copenhagen, Denmark this week must agree to encourage more sustainable land use.

The agricultural sector could go a long way toward being 'carbon neutral' by 2030 and producing enough food for nine billion people by 2050 — but only if farmers are encouraged to adopt land use practices now proven to be effective. These include agroforestry (including planting fertiliser trees) and minimum tillage (where fields are left unploughed before sowing).

Agroforestry has huge potential. Over one billion hectares (46 per cent) of agricultural land have more than ten per cent tree cover and are home to almost 600 million people. The trees provide fruit, livestock fodder, medicines, fuel and much else.

They also help lock up vast quantities of carbon. Our research suggests that expanding agroforestry could remove up to 50 billion tonnes of carbon dioxide from the atmosphere over the next 50 years. This is equivalent to one-third the amount we need to remove to halt global warming.

Other practices, such as minimum tillage — first adopted to prevent wind erosion in the American Midwest after the 1930s dust bowl — can further improve soil quality and crop yields.

In Zambia, the fertiliser trees are part of a sustainable agriculture programme funded by the Norwegian government that is now benefiting more than 160,000 families.

In neighbouring Malawi, at least 200,000 families — about 1.3 million of the country's poorest people — are improving their soils, increasing their food production and enhancing their nutrition through agroforestry, thanks to the assistance of Irish Aid.

At the 2007 climate change conference in Bali, negotiators decided that reducing emissions from deforestation and forest degradation (REDD) should be a key component of any future agreement. That makes good sense, as deforestation contributes approximately 20 per cent of global emissions.

But the scope of REDD should be broadened to include all land uses. We need a firm commitment in Copenhagen to provide the measures and financial incentives needed to encourage the transition to sustainable forms of agriculture.

It is likely that a legally binding climate deal will not be reached in Copenhagen and that negotiations will continue well into next year. But it is imperative that world leaders at least agree in outline, if not in precise detail, to firm targets and commitments.

Evergreen agriculture can help us to avoid a grim future of more poverty and hunger, and even greater climatic instability.