Historical nutrient usage in coastal Queensland river catchments adjacent to the Great Barrier Reef Marine Park

Abstract

The land catchments of the North East Coast Drainage Division which is adjacent to the Great Barrier Reef, occupy about 42 million hectares, about 20% larger than the continental shelf which supports the reef. Land use practices in these catchments depend on landform, climate, availability of ilTigation, soil types and the economics of adapting natural conditions to produce various horticultural and agricultural crops. Most of the soils of the region, the exception being some recent alluvia, are naturally deficient in the major elements, nitrogen, phosphorus and potassium. Addition of these has been neceSS31Y for large-scale crop production, particularly sugarcane and fruit and vegetable crops. Concell1 has been expressed that the movement of nutrients and eroded sediments from the adjacent land presents a serious threat to the complex ecosystem of the reef. Estimates indicate that the current movement of some nutrients from the terrestrial to the marine environment may be up to four times that which occurred pre-development. There is a need to quantify nutrient transfers at the catchment level, so that management practices can be modified where necessary, to prevent degradation of the reef environment.