The number of commercial vessels that are expected to pass through the reef in 2020, up from about 4 000 in 2012, according to the Great Barrier Reef Marine Park Authority. The number is expected to rise to 10 000 in 2032. More ships passing through the reef will mean greater chances of accidents and groundings, oil or chemical spills, and damage from the dropping of anchors. Ships sometimes also discharge harmful waste, cause pollution through illegal dumping, and introduce invasive species. More traffic also increases the risk of wildlife ship strikes, and the noise ships make can cause hearing loss in marine species, as well as the displacement and the stranding of such animals. Since 1993, there have been at least five vessel collisions and nine groundings by piloted ships in the Great Barrier Reef.