ABSTRACT
Shifting agriculture in the tropics has been replaced by poor, sedentary smallholders each farming a few hectares of degraded land with little or no opportunity to improve their crop yields using conventional modern agricultural techniques. However, for these farmers, trees can be used to overcome the environmental, social and economic constraints to production and to improve their livelihoods. Trees have two prime roles: (1) to create the habitat and ecological niches for the organisms that can recreate a functioning agroecosystem, and (2) to generate the income that is both an incentive for farmers to plant trees and a route out of poverty. Together these roles provide the means to improve farmers’ living standards and lifestyles. To address low yields and low income, both the soil fertility and the agroecosystem functions can be improved by planting nitrogen-fixing trees, and the cultivation of indigenous tree species producing nutritious and marketable products. This diversification of farming systems with agroforestry food and non-food trees results in increased staple and cash crop yields, as well as income, dietary diversity and provision of essential nutrients. Meanwhile, the domestication of useful shade trees as new tree crops creates an upper shade canopy that is environmentally beneficial and more profitable. Within such systems there are also niches for useful/marketable herbs in the understory. Biodiversity studies reviewed here indicate that species diversity in the shade trees and the understory promotes biodiversity, and supports the natural predators that reduce the numbers of herbivores and pathogens. To date, evidence mostly comes from coffee and cocoa agroforestry, but it is clear that this unconventional approach to tropical agriculture can rehabilitate degraded land (taking pressures off natural forest) and offer a way to productive and wildlife-friendly farming systems that improve food and nutritional security, as well as alleviating poverty.
