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.

Editor's Note

Aloha Overstory readers-- This edition we have a special guest author, Roland Bunch of COSECHA, Honduras. This summary of an article by Roland describes his discoveries during the course of 12 years of work in the humid tropics. His work with farmers revealed five key principles in agriculture for sustainability, based on the natural processes of fertility found in humid tropical forest ecosystems:

1. Maximize organic matter production
2. Keep the soil covered
3. Use zero tillage
4. Maintain biological diversity
5. Feed plants through the mulch

While we normally keep Overstory issues to one topic or concept, we hope you will enjoy Roland's summary of these interlinked principles.

Selected Tree Seed: improved returns in the short-term, viable populations for the long run

For generations, people all over the world have unwittingly been depleting the gene pool of many important trees by cutting down trees with the best characteristics, and leaving behind the inferior ones. Hundreds of forestry and agroforestry tree species have also suffered from severe genetic loss due to indiscriminant deforestation.

It is crucial that reforestation, forestry and agroforestry projects make strides to improve the gene pool by propagating seed from carefully selected trees. By utilizing the highest quality selected seed and plant material available, you can begin to reverse the trends of genetic degradation while improving the productivity and health of your plantings.

Editor's Note

This Overstory is about a shift in thinking that will enable us to transform our management practices from resource exploitation to resource renewal. This issue focuses on the philosophical foundation that underlies all the practical information you normally see in The Overstory. We see two key transformations in thinking. One is a shift from looking at strictly as one yield or function, to seeing a system as a whole. The other is a shift from approaching resources with an exploitative agenda, to actively designing and re-creating entire resource systems in a way that can benefit all life.

The significant problems we face cannot be solved at the same level of thinking we were at when we created them. -- Albert Einstein

Up until a few decades ago, most agriculture and resource management focused on manipulating, mining, and harvesting the vast bounty of nature, using resources that had built up naturally over thousands of years. Our task now is to do more than to stop the degradation. We have got to actually reverse the damage, restore natural processes, and manage in a way that resources are not only conserved and but built up over time. To accomplish this will require a fundamental shift in the way we think and work with nature and agriculture. It is a shift from from exploiting resources to actively designing and re-creating resource systems that can mimic nature in form and function.

Microcatchment: Making the Most of Limited Rainfall

Establishing tree plantings in dry climates presents great challenges. Infrequent rains are often too little to soak deeply into the soil. On the other extreme, occasional rainstorms generate rapid run-off, with little water absorbed by the soil. This run-off can cause erosion and other problems downslope.

Rather than resorting to expensive irrigation systems or earthworks (which may not be economically feasible) we can use nature's own models for sheltering and establishing new vegetation in dry climates. In nature, new vegetation often first takes hold in pits, cracks, crevasses, and at the base of large rocks. These special areas act as small catchments, collecting rainfall and allowing it to soak into the ground. These are natural "microcatchments." Small amounts of rainfall which otherwise would not soak deeply enough into the ground to help plants, trickle to the bottom of microcatchments and can contribute significantly to soil moisture.

Multipurpose Trees: Key Components in Agroforestry

While all trees can be said to serve several purposes, such as habitat, shade, and soil protection, some trees really stand out in their usefulness. Such trees are called "multipurpose trees"-- trees with the ability to provide numerous products and perform a variety of functions in farming or forestry. Multipurpose trees can be integrated with farming and forestry to improve yields, diversify products, increase economic resiliency, and improve farm viability and sustainability in the long-term.

Multipurpose trees are key players in supporting an overall farm system. When you plant a multipurpose tree, a number of needs and functions can be fulfilled at once.