BOGOR -- We need to know more about how smallholder agroforestry can help farmers adapt to climate change, write James Roshetko and Rodel Lasco.
Much is known about agroforestry — the mixing of tree species with crops and livestock to enrich farmers' livelihoods. But less is known about how it can help farmers adapt to climate change.
This gap in our knowledge is increasingly worrisome. With weather patterns becoming more erratic, farmers around the world are finding it increasingly difficult to know when and what to plant, risking shortfalls in food yields.
South Asia and South-East Asia alone are home to more than one-third of the world's population and half of the world's poor and malnourished. Without new approaches to food production, climate change in these regions could reduce agricultural productivity by as much as 50 per cent in the next 30 years. With agriculture serving as the backbone of most economies in these regions, such plunging yields could have severe consequences. 
Understanding what strategies farmers can use to cope with climate variability and extremes of weather is an essential first step towards mitigating climate change and adapting to its impact.
Increasing demand for wood and other tree products are sure incentives for farmers to cultivate a wide range of tree species. 
However, agroforestry also brings environmental benefits: it replenishes soil fertility, protects water catchments, conserves biodiversity, reforests otherwise denuded areas and reduces production pressure on natural forests.
Less recognised though, is agroforestry's potentially valuable role in climate management.
On a per area basis, tree-rich smallholding systems accumulate a significant amount of carbon comparable with that of some secondary forests. The carbon storage of such smallholdings also greatly exceeds that stored by the kinds of low-biomass systems that smallholdings replace — such as fallow agricultural land and grasslands.
What tree species farmers cultivate and how they manage them affect the amount of carbon stored. For maximum carbon storage, farmers should limit the amount of timber they harvest and keep low-biomass species, such as coconuts and banana, to a minimum. However, these considerations must be balanced with the farmer's need to make a living.
To farmers, carbon is even less tangible than other environmental services, such as watershed protection or biodiversity conservation. Carbon payments to farmers would increase their understanding of the services their agroforestry systems provide. Any income received for carbon should be treated as an additional return for the services such systems already provide. 
Protection from the storm
A recent study at the World Agroforestry Centre in Vietnam found that smallholders grew trees on their farms to shield themselves from unpredictable weather.  Those trees also stored carbon, thus contributing to mitigating climate change.
The residents of Cam My commune in Central Vietnam who participated in the research described their locality — which experiences heavy monsoon rains alternating with extended droughts — as 'a pan of fire in the hot season and a sink of water in the wet season'.
This would ordinarily spell disaster for farmers but the fruit, nut and berry trees the farmers kept on their farms along with crops and livestock were much more resilient than annual crops such as rice and maize.
The Cam My study pointed to the need for more research on growing crops under trees as a way to expand food production and increase food security. This is important because there is now little land available to convert for further agricultural production.
Some research is underway. A preliminary study in Indonesia has shown that vegetables can be grown in 'medium-light' methods — in the understory of a mixture of fruit, timber and banana trees. 
This method was found to be more productive and profitable than growing crops in areas without trees. More labour was needed to cultivate crops in the open and the technique didn't always produce the greatest yields. More research should be carried out to test these findings in other settings, and to learn how other farmers and systems adapt.
A review of tree domestication — the process of accelerating tree evolution to increase productivity on farms — showed that smallholders' agroforestry systems have developed significantly in the past 20 years to become more sophisticated, intensive and responsive to market demand. 
More work ahead
How can individual agroforestry systems be improved and expanded in different environments? We must learn more about this, perhaps by developing a comprehensive understanding of the value of trees and their genetic resources to the livelihoods of rural communities, and by reviewing the contributions of smallholders' agroforestry systems to the conservation of tropical tree diversity.
These are just some of the areas that need further research. Essentially, the entire chain — from seed collection, through harvesting wood or fruits and nuts, to marketing — needs more intensive and comprehensive study to ensure the security of our food supply, the livelihoods of hundreds of millions of people and the protection of our environment.