Ecological mechanisms underlying the sustainability of the agricultural heritage rice-fish coculture system

摘要

Modern agricultural practices face the challenge of producing sufficient food while minimizing potential negative effects caused by excess resource or energy use and pollution (1, 2) and therefore require "rethinking". Within this context, the value of traditional agricultural systems (3, 4), which have contributed to food and livelihood security throughout the world for centuries (4), should be reconsidered. Quantifying the ecological legacy of traditional agricultural systems may help us develop unique methods of sustainable agriculture. For example, traditional Chinese rice-fish coculture (RF) is a "globally important agricultural heritage system" (GIAHS) that has been maintained for > 1,200 y. Here, we conducted field surveys and experiments to elucidate the ecological mechanisms that contribute to the sustainability of this system by comparing RF with modern rice monoculture (RM). We found that RF requires 68% less pesticide and 24% less chemical fertilizer than RM, due to a mutually beneficial relationship between rice and fish through reducing pests and regulating nitrogen (N) levels. Hence, modern agricultural systems might be improved by exploiting natural synergies between species. The Chinese rice-fish coculture system was selected as a GIAHS by the Food and Agriculture Organization, the United Nations Development Program, and the Global Environment Facility in 2005. Rice-fish coculture is considered a sustainable form of agriculture, because it maximizes the benefits of scarce land and water resources by using relatively fewer chemical inputs, by producing both carbohydrate and protein products, and by conserving biodiversity compared with modern agricultural "monoculture" crop systems (i.e., rice monoculture). In our study area, despite other changes (i.e., improvement of farmers' livelihood and intensification of agriculture) resulting from the rapid development of China over the last 30 y, above half of the farmers continue to practice rice-fish coculture. Although the value of rice-fish coculture has been recognized, the ecological mechanisms underlying the sustainability of this system have not been studied in depth.