Mainstreaming Biodiversity in Agricultural Development

• Author: Stefano Pagiola/John Kellenberg/Lars Vidaeus/Jitendra Srivastava
• Position: Economist in the Global Environment Division of the World Bank's Environment Department/Consultant to the World Bank's Latin America and the Caribbean Regional Office/Chief of the Global Environment Division of the World Bank's Environment Department/Principal Agriculturalist in the World Bank's Europe and Central Asia Regional Office
• Pages: 38-41

The expansion and intensification of agriculture have been major contributors to the loss of biodiversity worldwide. As agricultural production continues to rise to meet the growing demands of the world's population, it is critical to find ways to minimize conflicts and enhance complementarities between agriculture and biodiversity.

Page 38

AGRICULTURAL expansion is a major contributor to the loss of biodiversity. Conversion of natural habitat to agricultural use substantially reduces its biodiversity. Naturally occurring plant species are replaced by a small number of introduced species (usually non-native and identical to crops produced elsewhere); wildlife is displaced; and insects and microorganisms are decimated by pesticides. There is also a change in functions, especially in energy and nutrient cycling and storage, as well as in water infiltration and storage. For example, the chart illustrates the substantially lower number of species found in agricultural landscapes compared with forest ecosystems in Borneo. Moreover, agricultural areas include more common species, while forest ecosystems tend to have more endemic and indigenous species. All types of conversion are not equally harmful, however. For example, some traditional agro- forestry systems in Sumatra contain as much as half the species diversity found in neighboring primary forest, a level substantially higher than those of other agricultural land use systems in the area.

What is biodiversity?

Biological diversity, generally shortened to biodiversity, encompasses all species of plants, animals, and microorganisms; the genetic variability within these species; and the ecosystems and ecological processes that form and sustain them. Biodiversity is more than just the number of species; it also includes their variety and uniqueness. Biodiversity can be measured at three different levels:

* Ecosystem diversity, or the variation in groupings of species and their habitats across the earth's surface;

* Species diversity, or the variety of different species; and

* Genetic diversity, or genetic variability within a species. Although biodiversity is often measured simply by counting species, their variety is also important. Introducing new, exotic species might increase the local species count, but it does not increase overall biodiversity. On the contrary, introducing exotic species, disturbing a habitat, or allowing natural weed species to invade may occur at the expense of native species that may be rare, threatened, or localized in their distribution (endemic). This will result in a net loss in overall biodiversity.

Agriculture can also affect biodiversity outside the areas on which it is practiced. Common opportunistic species tend to move into areas where natural and agricultural land uses meet and displace local or endemic plants and animals. Agricultural areas frequently break up the remaining natural areas, which affects Page 39 the number and types of species they can support. Management of water for agricultural purposes can substantially affect the timing, volume, and speed of water flow, and the replenishment of groundwater, altering natural aquatic and riparian habitats. Pollution by agrochemicals exacerbates these problems. In addition, agriculture's supporting infrastructure (including roads, irrigation systems, and farm housing) can also significantly affect biodiversity.

Although extensive agricultural growth is the main threat, intensified cultivation of existing agricultural land can also damage the remaining biodiversity. On-site biodiversity can be reduced because of increased specialization and reliance on a few improved crop species, while off-site damage can increase through increased use of chemical fertilizers and pesticides.

Such damage threatens the many important benefits provided by diverse ecosystems. Although the specific benefits provided by any given ecosystem vary substantially, they often contain a variety of economically useful products that can be harvested or that can serve as inputs for production processes. Diverse ecosystems also provide economically valuable services, such as improving water...