Human-induced impacts

Human activities influence both the availability of freshwater and the water quality. Humans use, and often pollute, water resources. For example, over-abstraction of water for human use has contributed to the depletion of available water resources, particularly groundwater resources, on a number of small islands (e.g.. Male in the Maldives). Increased development, particularly residential development, on even the smallest of islands has led to contamination of underlying or nearby aquifers and surface waters. Contamination from domestic animals, such as pigs and dogs, is also a problem on many islands. In addition, many islands are at risk from chemical pollution from such sources as fuel storage facilities and agricultural activities. In order to maximise food production, native vegetation is often cleared for cash crops and is sometimes accompanied by irrigation, which increases the use of available water resources, and the use of agro-chemicals (e.g., fertilisers, herbicides and insecticides), which are potential contaminants of available water resources. In the case of taro, which is commonly grown in pits dug down to the water table on coral atolls, insecticides are sprayed directly onto the crop. Traces of potentially hazardous organic waste have been found in water supply wells on some islands (e.g., Oahu and Maui in the Hawaiian Islands). In extreme cases, where available water on an island has become fully utilised or polluted to such an extent as to be unusable, off-island sources of water, or more expensive on-island water resource development technologies, must be used.