An estimated 67% increase in coal shipments by 2016 through Australia’s Great Barrier Reef could harm the marine habitat, environmentalists fear.

The reef is a breeding ground for humpback whales and is host to the world’s largest collection of coral.

Southern Cross University professor Peter Harrison said it was only a matter of time before a serious oil spill occurs unless there is a better system for regulating the traffic, reports Bloomberg.

According to a Gladstone port official, trade may rise by up to 140 million tons in six years from 84 million tons in the year ending in June.

The news comes in the aftermath of a Chinese tanker which remains stuck on the reef after attempting to take a short cut on its way back to China.

Nearly 1,500 ships are expected to pass through Gladstone this year, an official at the port said.

Gladstone will also be the port of departure for liquefied natural gas vessels from 2014.