'Evergreen agriculture' wins for climate and hunger

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.

Agroforestry tackles climate change

Agriculture - and deforestation and other changes to the land - account for nearly one-third of global emissions. To successfully tackle climate change, it is as important to curb these emissions as those generated by burning fossil fuels.

For that to happen we must agree to encourage more sustainable land use.

The agricultural sector could go a long way towards 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 10 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.