Agroforestry, as defined by the World Agroforestry Centre, is “a dynamic, ecologically based, natural resources management system that, through the integration of trees on farms and in the agricultural landscape, diversifies and sustains production for increased social, economic and environmental benefits for land users at all levels” (World Agroforestry Centre, n.d.). On the other hand, the Association for Temperate Agroforestry describes it as “an intensive land management system that optimizes the benefits from the biological interactions created when trees and/or shrubs are deliberately combined with crops and/or livestock” (Association for Temperate Agroforestry, n.d.).
Essentially, agroforestry refers to the practice of deliberate growing of trees in conjunction with crops or livestock for benefits and services (Nair, P.K.R., Kumar, B.M., & Nair, V.D., 2009).
(Schoeneberger, M.M., 2008)
Air Quality: Windbreaks and shelterbelts are two types of agroforestry practices that involve planting trees in long lines to protect crops and livestock. These practices also prevent soil erosion by wind and filter airstreams to remove particulate matter, such as odor particles that originate from livestock in grazing lands, which results in the mitigation of odor (Jose, S., 2009).
Water Quality: Agroforestry systems can prevent surface runoff from carrying extra fertilizer into water supplies. Riparian buffers, or trees grown along bodies of water, slow runoff and promote infiltration, sediment deposition, and nutrient retention. Additionally, the deeper roots and longer growing seasons of trees compared to agricultural crops create a more efficient use of nutrients (Jose, S., 2009).
Lower Needs for Fertilization and Irrigation: The use of nitrogen-fixing trees reduces the need for nitrogen fertilizer, while other non-nitrogen-fixing trees recycle nutrients and add biological matter to improve general soil quality (Jose, S., 2009). Planting trees with crops also improves water retention in the soil while the shade from trees slows water evaporation and the root systems help the soil store water. (Kandji et al., n.d.).
Biodiversity Conservation: Agroforestry provides a habitat for species that can tolerate some level of disturbance and can preserve the germplasm (genetic resources) for sensitive species by utilizing these sensitive species in agroforestry projects. Agroforestry can also prevent the destruction of more natural habitats by providing a more sustainable and productive alternative to traditional agricultural practices that may involve the clearing of natural habitats, as well as providing corridors to link fragmented habitats to help preserve these habitat remnants and the unique species living within. In addition to all of this, agroforestry can protect the surrounding environment through services such as erosion control and water recharge (Jose, S., 2009).
Farmers, especially those in developing nations, have the incentive to use agroforestry because extra income can be derived from tree products. Additionally, in extremely hot conditions, the shade from the trees improves the efficiency of photosynthesis of crops, which would normally suffer from heat damage and high transpiration rates. The trees also provide a more diversified income that protects farmers in the case of a poor harvest (Kandji et al., n.d.).
Shading from trees may reduce crop yields, though the income from tree products compensates for the loss in yield (Kandji et al., n.d.)
One of the main obstacles to implementing agroforestry worldwide is the need for education about agroforestry practices. The different systems of agroforestry require more skill and training than traditional agriculture. This is a problem in developing countries that lack the resources to educate their farmers. However, this problem can be solved by providing funds for education through a carbon cap and trade system.
Potential Storage Sites:
One model estimates that a total area of 585-1,215 million hectares of land in Africa, Asia and the Americas is currently utilizing agroforestry practices (Dixon, R.K., 1995).
The IPCC estimates a global amount of 630 million hectares of unproductive croplands and grasslands that could be converted to agroforestry by 2010 (IPCC, 2000).
Carbon-sequestration potentials vary from 0.29 metric tons of carbon per hectare per year in fodder banks (trees and shrubs grown as food for livestock) of the West African Sahel to 15.21 metric tons of carbon per hectare per year in mixed species stands of Puerto Rico (Nair, P.K.R., Kumar, B.M., & Nair, V.D., 2009).
One model estimated a global potential to sequester 1.1-2.2 gigatons of carbon per year over 50 years (Dixon, R.K., 1995). However, using the median carbon sequestration potential used by Dixon in that model (1.88 metric tons per hectare per year) and the estimate of total land area under agroforestry (1,023 million hectare) made by Nair et al. (2009) results in a carbon sequestration potential of 1.9 gigatons of carbon per year over 50 years.
There are approximately seven gigatons of carbon dioxide being sequestered by current agroforestry projects each year. However, in order to increase the amount of carbon sequestration, new agroforestry projects must be implemented in the remaining 3,953 million hectares of croplands and pastures in the world. The IPCC estimates a global amount of 630 million hectares of unproductive croplands and grasslands that could be converted to agroforestry and could potentially sequester 1.43 megatons of carbon dioxide per year by 2010 and 2.15 megatons of carbon dioxide per year by 2040 (IPCC, 2000).
- A case study performed on the Sahel region of Africa calculated the cost for establishing an agroforestry system (Sahelian Eco-Farm or SEF) with millet crops. The researchers estimated the cost per hectare to be approximately $60 for plant materials and a one-time application of $10 of fertilizers.
- The average income of the farms was $600 per hectare each year, twelve times the income of a typical millet farm without agroforestry. US$360 of this profit was derived from tree products (Kandji et al., n.d.). If one assumes that the total carbon sequestration potential of this area to be 106-194 metric tons of carbon dioxide per hectare (Dixon, R.K., K.J. Andrasko, F.A. Sussman, M.A. Lavinson, M.C. Trexler and T.S. Vinson, 1993), the cost per tonne of CO2 sequestered is US$0.36-0.66.
Agroforestry can be started in the near future, with as many as 630 million hectare of unproductive croplands and grasslands able to be converted into agroforestry land by 2010 (IPCC, 2000).