Millions of dollars worth of income could be unlocked for poor farmers in developing countries by changing existing policies that reduce investment in agroforestry.

Almost half the agricultural land in the world, about a billion hectares, has more than 10 percent tree cover, but there is still huge potential to increase the number of trees on farmland and improve their productivity.

Incorporating trees within farming landscapes, or agroforestry, can increase soil fertility, raise and sustain yields, increase income through the sale of timber and other tree products, and produce fodder and fuelwood.

To encourage the formation of a global partnership to unlock this untapped potential, the Nairobi-based World Agroforestry Center on Wednesday launched an Agroforestry Policy Initiative that aims to support policy reviews and reforms that will stimulate agroforestry and benefit rural people.

"This Initiative will support national and local policy reforms that will reduce barriers and improve incentives for private investment in agroforestry," said Dennis Garrity, director general of the center.

"Agroforestry can deliver a wide range of benefits. It can enhance food security, improve rural livelihoods, make better use of scarce rainwater and absorb atmospheric carbon."

Garrity said in many rural settings, trees provide subsistence needs and people can earn money from the sale of fruits, nuts, leaves and animal fodder, high value oils, gums and resins, timber and fuelwood for cooking, and medicines from various parts of trees.

A study of around 1, 000 smallholders in Kenya found that 55 percent sold fruits to earn income. This is more than those who sell the country's major staple crop maize.

In Haryana and surrounding states in northern India, hundreds of thousands of smallholders are growing poplar trees within irrigated wheat and barley fields, and this is generating about 1 million U.S. dollars a day for the growers.

Even in areas where tree cover is low, the impact of trees can be high. In the Sahelien parklands, critically important species such as Faidherbia albida, baobab and karite provide income of up to 325 dollars per year for households, together with food, fodder and fertilizer.

International trade in shea butter provides substantial foreign exchange earnings for West African countries like Burkina Faso.

According to the study, revising outdated policies and forest regulations will allow farmers in many countries to take full advantage of growing trees on farms, providing them with a lucrative source of income.

For example, following reforms to the Code Forestier in Niger, farmers have again been cultivating trees and the country has seen a tremendous increase in tree cover on over 5 million hectares in the past 20 years.