16 Nov1998

Overstory #21 - Agroforestry and Biological Diversity

Written by Kim Wilkinson and Craig Elevitch.

Agroforestry plantings should not be considered a replacement for the conservation of native tropical forests, but agroforesters can play a key role in helping to conserve biological diversity (biodiversity) of species. Agroforestry plantings can provide expanded habitat for a wide range of species, from soil microlife to insects to mammals.

How much benefit can agroforestry plantings have for biodiversity? In Latin America, for instance, numerous studies have shown that the traditional coffee agroforests (coffee integrated with 2-5 other tree species) are second only to undisturbed tropical forests in their diversity of birds, insect life, bats, and even mammals. For example, The Smithsonian Migratory Bird Center discovered at least 180 species of birds in Mexican coffee agroforests--up to ten times more than the bird diversity found in monoculture coffee plantations studied elsewhere. In the lowlands of Sumatra, resin-producing agroforests planted several generations ago are now some of the last reservoirs of biodiversity in the region, harboring rare epiphytes and herbs as well as 46 species of mammals, 92 species of birds, and much of the native soil fauna. (See references below for further reading.) Many effective conservation organizations now include agroforestry as a component of their programs.

The value of agroforestry for biodiversity is especially high when agroforestry replaces or expands into pastures or monoculture plantations or farms. A well designed agroforest, modeled after healthy, diverse natural forests will spontaneously attract and support biodiversity. While most of us have productivity as a primary focus, there are some things we can do to optimize the positive impact of our plantings on biodiversity.

Six Tips to Improve Biodiversity in Your Planting

As a general rule, the more forest-like in form and diverse in species a planting is, the more kinds of life it will attract and support. Here are some design tips that can help your agroforestry project become a safe harbor for biodiversity in your area:

Create a variety of habitat niches for wildlife--overstory, understory, and ground layer. If feasible, avoid clean culture in your management practices. Instead, leave some dead logs, leaf litter, scrub, etc.
Provide shade. Shady conditions are prevalent in natural forests, and shade fosters a wide range of species, from larger animals to soil microlife. If you have some practices on your project that require sunny open spaces (annual crops, open pasture, etc.), remember that most wildlife does not like to cross open spaces. Use open spaces in smaller patchworks throughout the project, rather than in a contiguous open area without overstory shade.
Create "wildlife corridors"--areas or zones of the planting that are not often disturbed or entered by people, leaving them to be colonized naturally. Ideally, connect these areas together to form safe corridors throughout the project, and connect them to neighboring habitats for wildlife.
Plant many different kinds of species. Complex, multi-storied agroforests have much more benefit than just one or two additional species integrated with a monoculture.
Conserve and store water on the land. In dry areas, water sources are especially attractive to wildlife. In addition to protecting natural streams or springs on the site, water-holding management practices like mulching, water catchment, ponds, and swales are also valuable.
If you are targeting a specific native species, learn about your intended guest's needs and plant the known food source, habitat environment, and other necessities to attract it. Encourage or actively cultivate native plant species within the project, as they are more likely to support native life, from soil fauna to birds. Also be aware of the exotic species that native wildlife may have become accustomed to as food or habitat that will also be of value. If you are near a native forest area, your chances of wildlife moving in spontaneously are greater than if you are isolated from natural areas. Contact a local biology school or conservation program for the information you need. They may also be able to help you identify the most important species in need of conservation support.

From an agroforester's perspective, it is important to recognize that the same practices that attract desirable wildlife may also attract species that could be problematic for production. In Hawaii, for example, wild pigs that cross through or reside in tree plantings may be welcomed by some projects, but may cause too much damage to trees or crops for others. In other areas of the world, species such as monkeys, fruit-eating birds, and other native animals may adversely affect productivity. If neighboring areas are sources for these kinds of wildlife, decide at the outset how you will exclude, manage, or possibly benefit from their presence. If necessary, you may be able to find ways to make up the revenues lost on crops directly from the biodiversity of your project-- through tours or field visits from people who want to see wildlife.

Ideally, large agroforestry plantings should work in cooperation with local conservation efforts (reserves, parks, and so forth) to optimize the benefit of the work.

Keep it up and who knows, your planting may one day be mistaken for a natural forest! If not by a person, at least by a wild creature who's happy to find a new home.

About the Authors

Kim M. Wilkinson is the Education Director for Permanent Agriculture Resources and editor of The Overstory. She has B.A. degrees in Anthropology and Ecology from Emory University.

Craig R. Elevitch is an agroforestry specialist with more than ten years of public and private sector experience in tropical agroforest and forest management. He has a M.S. degree in Electrical Engineering (Dynamical Systems) from Cornell University.