Two species of coffee are grown commercially. Coffea canephora, or robusta coffee, is an often bitter species that is usually considered low quality and is used as a filler in cheap grocery store coffee. The higher quality arabica coffee, Coffea arabica, is an understory tree or shrub which naturally grows in shade. However, mostly with an eye toward profit, there has been a movement to find ways to grow arabica coffee in the sun.
Coffee is grown on nearly 10 million hectares in tropical regions around the world, areas that also harbor high levels of biodiversity. In the 1990s, farmers were encouraged to replace traditional shade grown coffee with sun cultivation in order to increase the yield of their coffee. In sun coffee systems, there is little or no canopy cover, and coffee trees are planted at high densities. In Latin America, 1.1 million of the 2.8 million hectares in coffee (41%) were converted to sun cultivation (Rice and Ward 1996). The impact of deforestation and conversion of shade coffee to sun coffee on biodiversity in these regions is much greater than the absolute levels of destruction would indicate.
While older arabica coffee varieties traditionally grown in the shade did not do well in the sun, they were replaced by hybrids that could withstand the sun and had more resistance to introduced diseases. But sun cultivation also has many other negative environmental impacts:
- In shade plantations, dead leaves from the overstory trees provide nutrients to the coffee. In sun plantations, these nutrients are not available, so fertilizers must be used, especially nitrogen (since many traditional overstory trees are nitrogen-fixing legumes). Sun coffee farms leach triple the nitrates into the local watersheds than shade farms.
- There are fewer weeds in shade plantations, both because of the shade itself and due to the fallen leaves from shade trees acting as a natural mulch. Herbicides are needed to control weeds in sun plantations.
- Soils in sun plantations are more exposed to the elements, particularly drenching rains typical of tropical areas. This leads to erosion of topsoil, and the leaching of chemical fertilizers, pesticides, and herbicides into local watersheds. Soil erosion and acidification and water pollution are serious consequences of growing coffee on sun plantations.
- Coffee plants in sun plantations grow faster and age more quickly than those grown in shade, and therefore must be replaced more often. Sun-grown coffee trees are typically productive for less than 15 years, while shade-grown coffee trees may yield for 30 years or more.
You can read more about the benefits of growing coffee in the shade in this post.
Donald, P. F. 2004. Biodiversity impacts of some agricultural commodity production systems. Conservation Biology 18:17-37.
Rice, R. A., and J. F. Ward. 1996. Coffee, conservation, and commerce in the Western Hemisphere. Smithsonian Migratory Bird Center and National Resources Defense Council.