Impacts of Land Use Change on Soil Erosion and Water Quality—A Case Study from Hawaii

The ongoing diversification of agricultural lands in Hawaii to replace sugarcane and pineapple plantations is a major challenge. It presents an interesting case study for global concerns with land degradation-land use interaction. The important question posed by this paper is: will “diversified” crops have a different impact on the natural resource base and environmental quality from earlier cropping systems? We used the revised universal soil loss equation (RUSLE) to examine a number of scenarios toward an answer to this question. Our quantitative predictions showed that annual crops grown with “conventional” practices would be considerably less protective against sediment losses than sugarcane. Orchards and short rotation bio-energy (fuel tree) plantings are also vulnerable during the early stages of tree growth, after full canopy, and during or following harvest or logging operations. Well-managed pastures represent a highly “protective” alternative. Similar arguments are made for impacts on contamination of surface and groundwater supplies by agrichemicals. Biological soil conservation options offer substantial promise for protecting soil and water quality under vulnerable land uses.