Trees in cropland
Trees absorb and store vast amounts of carbon throughout their life. Farmers can plant trees on croplands to provide windbreaks and shelter for crops, prevent erosion, diversify production and maintain moisture levels, while reducing carbon emissions. Planting trees in croplands can be done on a large share of the world’s agricultural lands without lowering production.
Trees could be planted in croplands across 608 million hectares worldwide – an area over half the size of the United States. We estimate that holding warming to below 2 degrees C would need the application of agroforestry systems across 322 million hectares, an area about the size of India.
Planting trees in agricultural lands could store 439 million tonnes of carbon dioxide equivalent per year (MtCO2e/year). That’s comparable to the emissions from 94 million passenger vehicles per year.
One of the main challenges to agroforestry systems lies in understanding and communicating the benefits to farmers, and providing them with the technical support and extension services to encourage them to shift to a new (sometimes counterintuitive) method of farming. Agricultural policies and incentives may need to be changed or created to promote the adoption of agroforestry systems.
More research is also needed to map the regions where various tree-planting practices are likely to have net economic benefits that offset the loss of agricultural area to trees.
Agroforestry could be applied to croplands worldwide, and the practice could be implemented immediately. While many different agroforestry systems have been demonstrated, three systems currently stand out:
- Windbreaks: planting belts of trees and shrubs to protect fields and homes from wind.
- Alley cropping: planting lines of productive trees within croplands.
- Farmer-managed natural regeneration (FMNR): managed recovery of native trees within dryland agriculture systems to protect and improve soils.
While some agroforestry systems are costly, others, such as FMNR, are very low-cost. In some regions, planting trees in croplands would bring net benefits.
Spotlight: Farmer-Managed Natural Regeneration in Niger
After extensive deforestation in the mid-twentieth century, much of Niger suffered from recurring drought, worsening soil erosion, dust encroachment and poor agricultural productivity. In the 1980s, during a national famine, local farmers in the Maradi district were required to practice forest-managed natural regeneration through a food-for-work program. The project encouraged farmers to protect and manage seedlings and regenerate tree stumps in their croplands, focusing on trees with agronomic benefits such as nitrogen fixation.
The efforts led to widespread recovery of tree cover, with a corresponding drop in soil erosion and an increase in soil fertility. As a result, crop yields surged. The economic benefits of the project were estimated at $56 per hectare per year. The project spread rapidly, and is now practiced on more than five million hectares in southern Niger.
Successful FMNR programs are happening in many other areas, including Ethiopia, Indonesia, Senegal and Timor-Leste.