Sea Urchin Versus Rock Lobster
You may not be aware of it, but here in south-eastern Australia we’re living in a climate change hot-spot. Thanks largely to strengthening and intensification of the East Australia Current (aka “The EAC dude!”), warm waters from the north are travelling further south for longer. While this is good news for Sydney swimmers, it’s having some pretty big impacts further south.
Many species previously restricted to mainland Australia are hitching a ride with this warm water current down to Tassie and wreaking havoc with the locals. One of the most conspicuous and destructive of these recent arrivals is the long-spined sea urchin, Centrostephanus rogersii. You may have seen these guys while snorkelling at Clovelly or Gordon’s Bay – they are very large sea urchins with long, black spines (most unpleasant to stand upon). They are also voracious herbivores and, en masse, so effective at removing seaweed that they create vast areas of bare rock known in scientific circles as urchin barrens.
Since arriving in Tasmania, these guys have gone to town, mowing down huge areas of seaweed and creating barrens for the first time in Tasmania’s recent geological history. With such substantial loss of kelp cover, some 150 different animals and plants that relied upon those underwater forests for food and habitat have disappeared.
This is bad news for biodiversity but also a big blow for local industry. The Tasmanian abalone and rock lobster fisheries are worth at least $150 million each year. Both of these animals rely directly upon kelp forests and seaweed beds for survival, so the Tassie urchin invasion is having a massive impact on these lucrative Tasmanian fisheries.
As environments change due to global warming and urbanisation, many species’ ranges are contracting, extending or disappearing altogether. Most animals and plants have an optimal ‘thermal envelope’, so when things heat up they need to move. In fact, some experts have estimated that species are moving towards the poles and up mountains in search of cooler conditions at an average astronomical speed of 6km per decade.
All these changes have led many prominent scientists to speculate ecosystems are currently undergoing a period of unprecedented change. In our little corner of the world, this appears to be happening faster than most other places and is, unfortunately, creating marine ecosystems with lower biodiversity.
Although somewhat abstract, we all like the idea of maintaining biodiversity. What we continually to fail to realise, however, is that these environmental impacts will, sooner or later, hit us in a much more tangible place: our hip pockets.
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