INTRODUCTION

Rainfed farming continues to expand in the humid tropics as the population grows, and natural forests are being replaced by agriculture on increasingly steep hillsides. This process may be abrupt but more often occurs through a series of gradual changes in land use: from forest modification, to shifting agriculture, through settlement mosaics and on to eventual complete forest replacement (Sayer et al., 2000). Often, the gradients in question are above theoretical legal limits for cultivation (Moldenhauer and Hudson, 1988) (Figure 38.1). The challenge is to identify and offer practical solutions for soil and water conservation in these areas that are both technically appropriate and socially acceptable. It is increasingly realised that measures must address water, fertility and production aspects simultaneously, as well as the prevention of surface erosion. These systems should be sound in technical terms so that they control damage to the soil and to the hydrological integrity of the hillsides. They should also sustain plant production. Social acceptability is the acid test of adoption: if ‘solutions’ are not attractive to land users they will not be sustained and they will not spread.

Since world-wide concern with soil erosion (‘the problem’) and soil conservation (‘the solution’) spread in the 1930s and 1940s, catalysed by the great dust bowl phenomenon in the United States (Anderson, 1984), there have been significant shifts in conceptual thinking. In summary, it has been recognised that top-down schemes based on engineering techniques have largely failed to deliver.