|Vetiver Grass: A Thin Green Line against Erosion (BOSTID, 1993, 157 p.)|
For developing nations, soil erosion is among the most chronic environmental and economic burdens. Many of these nations are in the tropics, where in just a few hours torrential downpours can wash away tons of topsoil from each hectare. Many others are in the drier zones, where swirling winds and flash floods (sometimes from rains so distant they are unseen) can be equally devastating.
By these processes, huge amounts of valuable soil are being lost every day. Worse, the soil accumulates in rivers, reservoirs, harbors, estuaries, and other waterways where it is unwelcome, terribly destructive, and impossibly costly to remove. Erosion is thus a double disaster: a vital resource disappears from where it is desperately needed only to be dumped where it is equally unwanted.
Despite much rhetoric and effort, little has been accomplished in overcoming erosion, at least when viewed from a worldwide perspective. One major reason is that there are few if any solutions that are cheap, appealing, long lived, and suitable for easy adoption over the vast expanses of the Third World that need protecting. Now, however, there may be one.
In the eyes of at least some viewers, a little-known tropical grass, vetiver, might at last offer one practical and inexpensive solution for controlling erosion simply, cheaply, and on a huge scale in both the tropical and semiarid regions. Planted in lines along the contours of sloping lands, vetiver quickly forms narrow but very dense hedges. Its stiff foliage then blocks the passage of soil and debris. It also slows any runoff and gives the rainfall a better chance of soaking into the soil instead of rushing off the slope. Although there has not been much experience with this process to date, the deeply rooted, persistent grass has restrained erodible soils in this way for decades in Fiji, India, and some Caribbean nations.
At least in this limited practice, vetiver appears truly remarkable. The grass itself seems not to spread or become a pest. Terraces rise as the soil accumulates behind the hedges, converting erodible slopes into stabilized terraces where farming and forestry can be conducted, safe from the evils of erosion. Farmers and foresters benefit not only by keeping their soil, but by having flatter land and more moisture for their plants. Countries benefit by having cleaner rivers, unspoiled estuaries, and more water and less silt in their reservoirs.
At present, however, no one knows for sure whether these experiences represent a practical possibility for solving the world's worst erosion problems. The purpose of this report is to make a judgment on this point: to assess vetiver's promise and limitations and to identify any research that may be necessary before this grass can be deployed rationally, widely, and without undue environmental risk. In other words, our particular purpose is to evaluate the ecological advantages and potential risks in employing a grass that may eventually benefit watersheds, forests, and farms throughout the world's warmer zones.
This book, it should be understood, is neither a monograph on vetiver nor a field guide for its use. It is, instead, a scientific audit of the safety and effectiveness of the plant as used for erosion control. Basically, the book reviews existing research and experiences with the grass. It has been compiled from literature, from personal contacts, from site visits, and from information mailed in by specialists in an array of disciplines: environment, agronomy, forestry, soil science, engineering, and others. Many contributors had little or no knowledge of vetiver itself; they served as "devil's advocates." We hope that this exhaustive process has produced an independent, unbiased evaluation that will help scores of countries and organizations judge whether or not to use this plant in their own programs.
The report has been produced particularly for nonspecialist readers such as government ministers, research directors, university students, private voluntary organizations, and entrepreneurs. It is intended primarily as an economic development document. We hope it will be of particular interest to agencies engaged in development assistance and food relief; officials and institutions concerned with environment, agriculture, and forestry in tropical countries; and scientific establishments with relevant interests.
This study is a project of the Board on Science and Technology for International Development (BOSTID), a division of the National Research Council, and is prepared under the auspices of BOSTID's program on technology innovation. Established in 1970, this program evaluates unconventional scientific and technological advances with particular promise for solving problems of developing countries (see page 158). The report continues a series describing promising plant resources that heretofore have been neglected or overlooked. Other titles relating to vegetative improvements for tropical soils and environment include:
· Tropical Legumes: Resources for the Future
· Leucaena: Promising Forage and Tree Crop in Developing Countries (second edition, 1984)
· Mangium and Other Fast-Growing Acacias for the Humid Tropics (1983)
· Calliandra: A Versatile Small Tree for the Humid Tropics (1983)
· Casuarinas: Nitrogen-Fixing Trees for Adverse Sites (1983)
· Firewood Crops: Shrub and Tree Species for Energy Production, Volumes I and 11 (1980 and 1983, respectively)
· Sowing Forests from the Air (1981)
· Neem: A Tree for Solving Global Problems (1992).
Funds for carrying out this vetiver study were made available by the following organizations:
· The Office of the Science Advisor of the U.S. Agency for International Development;
· The Environment and the Agriculture and Rural Development departments of the World Bank; and
· The Soil Conservation Service of the U.S. Department of Agriculture.
Additional funds for printing the report were contributed by the International Tropical Timber Organization as well as by the following departments of the World Bank: Agriculture and Rural Development, Environment, External Affairs, and Asia Technical. The following World Bank country divisions also contributed: South Asia, East Asia, Latin America, and Africa.
How to cite this report: National Research Council. 1993. Vetiver Grass: A Thin Green Line Against Erosion. National Academy Press, Washington, D.C.