The Destruction of the Kelp

Kelp on White Beach, Tasmania, December 2009.

Kelp, a large seaweed that grows in underwater forests along temperate coasts, supports many marine species in turn. The Kelp Highway Hypothesis postulates that Pacific Rim kelp forests and the wealth of fish, mammals and birds that they supported sustained maritime hunter-gatherers spreading into the New World 16,000 years ago. Kelp species play an important role in Chinese, Japanese, and Korean cuisines, and fuelled the production of soda ash in the Scottish Highlands and islands until the industry’s collapse in the 19th century, which fuelled emigration to North America and beyond. Charles Darwin wrote of the kelp forests of Tierra del Fuego that “if in any country a [terrestrial] forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp”.

In October 2016, an ocean heatwave destroyed the last giant kelp forest on the east coast of Tasmania, bringing an end to an ecosystem that has dominated it for tens of thousands of years.

A few months earlier, a study revealed that ninety percent of the kelp forests that make up the north-western tip of the Great Southern Reef disappeared off the Western Australian coast between 2010 and 2013, forests which had supported some of the most valuable fisheries in the country. And a few months before that, US scientists reported that large tracts of kelp forest along the coast from San Francisco to Oregon have vanished over the past two years, with similarly grim implications for fisheries. Around the world, kelp forests are declining as tropical fish species move into warmer waters and eat them.

I grew up in southeast Tasmania, and used to go camping and day-tripping with my family along the east coast. Walking along empty white sand beaches is part of my fondest memories and my favourite pastime when visiting home. Except they were never empty: they were littered with kelp, which grew in a tangled yellow-green mass off the lichen-red rocks at the end of every beach, like flat noodles swirling in miso soup. A fish-farmer friend would skin-dive in the kelp forests off Bruny Island and surface with buckets of abalone, and share them with us on weekends at his shack. We would fish from his dinghy for flathead that lived in those waters, whose numbers are now declining; I don’t know whether this decline will be hastened by warming waters and the loss of kelp, but expect it will.

A lot of attention and dismay has focussed on the devastation of corals along the Great Barrier Reef and elsewhere in recent years, for good reason, but this loss of temperate kelp forests feels just as significant. When climate change deniers crack wise about how it can’t be warming because there’s still snow, this is what I want to confront them with. I want to take them to a rocky shore and stick their heads in the warm water to witness this, and see if they can splutteringly maintain that everything’s fine.

In the silver-lining department—though it isn’t much of one—if the tropical seaweed Asparagopsis taxiformis could be grown and harvested in these newly warmer waters and fed to cattle, it could reduce agricultural methane emissions significantly.

[Edited from a post and comments at Metafilter.]

15 December 2016 · Events