CONTENTS
HIGHLIGHTSPopulation Reports is published by the Population Information Program, Center for Communication Programs, The Johns Hopkins School of Public Health, 111 Market Place, Suite 310, Baltimore, Maryland 21202-4012, USA
December, 1997 |
Already, the productive capacity of much arable land is diminishing because soil is becoming degraded. Worldwide, nearly 2 billion hectares of crop and grazing land an area larger than the United States and Mexico combined suffer from moderate to severe soil degradation. The main causes are soil erosion, loss of nutrients, damage from inappropriate farming practices, and the misuse of agricultural chemicals (8, 27, 98). In the Philippines, for example, an estimated 1.2 million hectares of cropland roughly one-fourth of the total have been severely degraded by pesticides and chemical fertilizers (67). Each year wind and rain erode an estimated 25 billion metric tons of topsoil from the world's croplands (25, 91, 99). China's Huang (Yellow) River alone empties 1.6 billion metric tons of eroded topsoil into the Yellow Sea each year (38). The United States has lost one-third of its topsoil since colonial times (25). |