About one-quarter of the Queensland land surface drains into the Great Barrier Reef World Heritage Area. Runoff of sediments, nutrients and other pollutants has increased several-fold since before European settlement, but the issue of impact on the reef has been contentions. Most of the sediment and nutrients come from cattle grazing. Sugarcane production also makes a disproportionate contribution to sediment, nitrogen and phosphorus discharge. Flood plumes tend to hug the coast and the greatest pressure due to runoff seems to be on some 200 near-shore reefs. Evidence for deleterious impacts on coral reefs is growing.