Agrodiversity: Learning from Farmers across the World. Harold Brookfield, Helen Parsons, and Muriel Brookfield, eds. United Nations University Press, New York, 2003. 343 pp., illus. $32.00 (ISBN 9280810871 paper).
This book from the United Nations University Press comprises information gathered from smallholder farmers, primarily in developing nations, and compiled by 40 authors representing 60 institutions in 17 nations. Edited by Harold Brookfield, Helen Parsons, and Muriel Brookfield, Agrodiversity: Learning from Farmers across the World describes how smallholder farmers conserve biodiversity on their farmland and in the surrounding environment. The effort is based on the fieldwork of the United Nations University Project on People, Land Management and Ecosystem Conservation (PLEC). This PLEC report examines in detail how farmers use knowledge and skill to manage resources, and illustrates diverse food production practices that have successfully protected diversity.
Food production is vital to farmers and the communities they serve because, as the World Health Organization (WHO) recently reported, approximately 3.7 billion humans are currently malnourished in terms of protein and calories, iron, vitamins, or iodine. Most hungry people are located in developing countries, and the WHO report documents the largest number of malnourished people in history. Cropland, as noted in Agrodiversity, is vital to food production and to farmers' economic well-being. The Food and Agriculture Organization of the United Nations (FAO) reports that more than 99.7 percent of world food (in calories) is produced from the land, and less than 0.3 percent comes from the oceans and other aquatic ecosystems. The percentage from the oceans is declining because of overfishing, pollution, and rapid human population growth.
Because cropland and pastureland are vital to farmers, PLEC places some emphasis on soil and water conservation. Some of the technologies that have been recommended for PLEC farms are using physical barriers such as logs and big rocks, planting across slopes, using minimum tillage, placing crop and weed residues on the soil surface, strip cropping, rotating crops, using living mulches, and using agroforestry. Ideally, soil erosion rates should be no more than 1 metric ton per hectare per year, because this is the rate of soil formation and thus of sustainability. High levels of organic matter in the soil are essential to keep the soil productive and to conserve water for the crops. Soil organic matter can act as a sponge to store water for crops when conditions become dry. A crop such as maize can require nearly 5 million liters of water per three-month growing season.
Large quantities of soil organic matter, along with the biomass above the ground, play an important role in conserving both below- and aboveground biodiversity. The farmers associated with PLEC recognize this relationship. Most of the crops grown by the farmers, such as rice, corn, wheat, and bananas, are exotic species introduced for food production; this is true worldwide. Humans have cultivated up to 20,000 species of plants for food, but today only 15 plant species provide about 90 percent of the world's food.
Although crop and livestock species cultured in agriculture are beneficial and essential to our food security system, some invasive species can be serious pests of agriculture, forests, and public health. In the United States, 73 percent of weed species in crops, and 65 percent of plant pathogens, are introduced species (Pimentel et al. 2000).
This volume on agrodiversity suggests that most plant, animal, and microbe species are associated with managed agricultural and forest ecosystems. In a crop ecosystem, as many as 95 plant species can be cultured by one farmer (Brookfield 2001). A current study in Guinea reported one household with 64 herbaceous species and an orchard with 39 species. The arthropods in a productive habitat may include 600 to 1000 species, and in the soil habitat bacterial species may number 20,000 (Pimentel et al. 2005).
The farmers associated with PLEC recognize that abundant plant biomass and belowground organic matter support the largest number of species. Therefore, one of their goals was to increase the abundance of plant biomass both above and below the ground. Of course, this increases not only the biodiversity of the agricultural ecosystems themselves but the biodiversity of the animal and microbe species that are associated with these systems.
Recent trends in crop production are not encouraging, as suggested by Harold Brookfield in his earlier book Exploring Agrodiversity (2001). The high costs of inputs (fertilizers, pesticides, and crop seeds) place significant stress on small farmers in developing countries. Although crop yields per hectare are still increasing, they are increasing more slowly than in the past because of shortages of cropland, degradation of agricultural land, and declining irrigation and fertilizer use per capita worldwide. Moreover, the FAO reports that grain production per capita has been decreasing for the past two decades. The decline in the per capita availability of these basic food grains, which make up about 80 percent of the world's food, is contributing to the incidence of malnourishment.
Brookfield, his coeditors, and the other 40 contributors are to be commended for assembling valuable information concerning PLEC. The authors provide insight on how innovative farmers around the world manage their natural resources with an interest in both conserving bio-diversity and engaging in efficient food production. Agrodiversity offers technically detailed information, based on the successful experiences of smallholder farmers, to agriculturists, agronomists, geographers, biologists, ecologists, plant breeders, agricultural engineers, anthropologists, and others interested in a world outlook on agrodiversity.