Wildlife

Death of Australia's other great reef a bad sign for world's kelp forests

Alarms sounded across the world when marine scientists discovered in April that more than 90 percent of the Great Barrier Reef, the world’s largest reef, had bleached. As the scientific community, the Australian government, and even President Obama placed calls to action to save one of the Earth’s great natural wonders, the death of the country’s other reef, the 1,400-mile Great Southern Reef, went unnoticed.

Nearly all of the kelp forests along about 62 miles of coastline off western Australia have become extinct following a heat wave in 2011 that killed 43 percent of kelp there, according to a study published Friday in the journal Science. And five years later, there are no signs of recovery, said the study’s lead author, Thomas Wernberg of the University of Western Australia’s Ocean Institute, in a statement.

The extinction of the expanse of kelp forests in the northwest tip of the reef shows the sensitivity of the ecosystem, and demonstrates how a slight rise in water temperatures (4 degrees F) can turn an underwater forest, teeming with life, into a desert of turf seaweed. Because the temperature of the Indian Ocean, the current of which flows south to the Great Southern Reef, is warming twice as fast as the rest of the world’s waters, the demise of the ecosystem also foreshadows the effect a further rise in water temperatures could have on kelp forests around the world, including in Japan and Europe.

The Great Southern Reef is composed of a system of rocky reefs that stretch more than 1,400 miles, from Brisbane in eastern Australia to Kalbarri above Perth in western Australia. The forests, whose seaweed branches extend to the surface like trees, are a global diversity hotspot, with 30 to 80 percent of species there not found anywhere else in the world.

The reef’s rock lobster and abalone fisheries also bring in four times the wealth of all the commercial fishing combined in the Great Barrier Reef.

For now, kelp forests further south along the reef are healthier, though there are concerns that more heat waves will continue to push the destruction southward. Scientists can mitigate the effects of warmer water, however, by controlling factors such as sewage run-offs, which weaken kelp.