10 - Tropical Stream Conservation

Abstract

This chapter focuses on the conservation issues that are relevant to most tropical regions and stream types. It also reviews the major factors impacting tropical streams. Conservation issues affecting tropical streams are complex and result from particular combinations of socio-economic factors and ecological responses. It reveals that the major factors impacting tropical streams are mainly over-fishing, deforestation, and water abstraction for irrigation and human consumption, pollution, and alterations in riverine connectivity. Most tropical regions have annual population growth rates of nearly 3% and this rapid pace of growth is commonly followed by over-exploitation of natural resources. The problem of over-exploitation of natural resources by developing countries is exacerbated by over-consumption in developed nations. On the other hand, the ecological factors include the increased rate of erosion of land after clearance for agriculture. Tropical streams located in coastal areas and island streams tend to be dominated by migratory fishes and shrimps that must pass their immature stages in estuaries or coastal waters. Deforestation is a major environmental problem in tropical regions, where rates of tropical forest loss currently exceed 1.25×105 km2 yr-1. Removal of catchment vegetation, in particular riparian vegetation, alters water movement from land to stream, resulting in increases in erosion and sedimentation in the channel. Loss of longitudinal and lateral riverine connectivity is one of the main results of river regulation, damming, and water abstraction. The case study shows that the abandonment of agriculture in Puerto Rico has had a positive effect on water quality, as chemically loaded runoff into streams has decreased.