Preservation of the environment on coral islands and intensification of agriculture: applied study on Maré, Loyalty Islands, New Caledonia

Abstract

Elevated Pacific coral islands form a particularly vulnerable ecosystem characterized by fragile soils, usually in thin layers, and by the presence of a fresh water lens that replenishes itself only slowly and is also in balance with sea water. This lens often constitutes the sole supply of drinking water and any pollution affecting it would irremediably jeopardize this vital resource. In the Loyalty Islands, population growth combined with more intensive agricultural methods (use of fertilizers, pesticides, machinery, irrigation), often ill-suited to this type of environment, may cause irreversible damage. Agricultural research must, therefore, now try to obviate the dangers by developing techniques that will protect the environment while allowing essential economic development to proceed. Thus, in 1993, CIRAD New Caledonia, in collaboration with ORSTOM, initiated a new multidisciplinary research project in the Loyalty Islands to investigate problems relating to intensification and stabilization of agriculture on coral islands. The methods involve combinations of different levels of intensification (soil preparation × fertilization rates) and crop rotation. Methods are investigated in conjunction with the major food crops grown in the region (traditional tubers, vegetables), as well as fodder crops. Trials are also under way for monitoring infiltration (nitrates and pesticides). After two years of experiments, the first results have been obtained on crops (yield, labour input), and changes in soil fertility (mineral and organic contents) with an intensive method.Keywordscropping systemspreservation of coral environmentsubsistence cropsLoyalty Islands