An economic analysis of revegetation for dryland salinity control on the Lower Eyre Peninsula in South Australia

Dryland salinity is a major natural resource management problem imposing large economic and environmental costs in many countries throughout the world. The major cause of dryland salinity is the replacement of perennial native vegetation with annual crops and pastures. This results in greater amounts of water entering a groundwater system, watertable rise and the concentration of naturally occurring salts near the soil surface. Many consider that the best long‐term solution is the re‐establishment of high water use perennial vegetation through production systems such as agroforestry. This paper presents a benefit–cost analysis (BCA) of revegetation to control dryland salinity over a 20‐year period in South Australia. The results of the BCA indicate that market costs are likely to exceed market benefits for broad‐scale revegetation programmes. These results are driven by hydrogeological studies, which indicate that as much as 50 per cent of a ‘problem‐type’ catchment needs to be revegetated to save only 3 per cent of land from being salt affected. The conclusion is that revegetation programmes need to be highly targeted to areas of a catchment with large potential to control salinity, land that has minimal value for other uses and regions with high infrastructure and ecological value. Copyright © 2002 John Wiley & Sons, Ltd.     

Factors influencing the intensification of farming systems and soil‐nutrient management in the rural‐urban continuum of SW Ghana

Farmers in Ghana use a variety of soil‐fertility management practices to optimize the benefits of shifting cultivation and/or to intensify their production. The research question was to analyze the relationship between these practices and the availability of the production factors land, labor, and capital. A farm survey along a gradient through SW Ghana showed that there is only a weak link between the intensification of traditional farming systems, population pressure, and reduced fallow periods as long as shifting cultivation is possible and common. Even where fallow periods reach a cut‐off point, farmers might look for land in remoter areas or invest in off‐farm activities. Only where market proximity supports the production of high‐value crops, investment flows are used to maintain continuous cultivation on favorable production sites, especially those with water access. The results verify the validity of the framework of agricultural‐systems dynamics in W Africa, developed by the International Institute of Tropical Agriculture (IITA) and the importance to distinguish between population‐driven and market‐driven situations. Both meet in periurban areas, which make them hot spots for research and development, while support for intensification is likely to fail where markets are far and shifting cultivation still an option.