Managing Salinity in Degraded Soils by Mandatory Tree Planting: On the Dynamic and Political Economy Modeling of a Common Pool Resource Ernst-August Nuppenau*

Many farming areas in the tropics and subtropics are characterized by increasing salinity. These areas include traditional, poorly managed, rain fed dry land farming areas as well as modern, extensively and intensively used irrigation schemes. In particular, intensification of agriculture due to human population pressure or increased economic incentives for land de-velopment have contributed to salinity. Salinity nowadays stretches over large landscapes in tropical and subtropical countries. Surface and ground water systems as well as deeper aquifers are heavily infiltrated, i.e. polluted with salt. Being largely an uncontrolled exter-nality of plant production under less appropriate technology, high salt content reduces productivity, noticeable as a common-pool externality. In particular, small-holder communities with low technological levels, short term needs for agricultural produce, and strong capital constraints have the tendency to overexploit water. Moreover, the potential of soils to regenerate from the tendency for salinity, declines with time. Due to the immanent common property problem of the media, water, as well as high trans-action costs in soil protection and non-point-pollution problems, salinity is the common fea-ture of poorly, publicly, managed irrigation schemes. Salinity levels of small-holder areas ar