Tropical Fish Are Taking Over Temperate Oceans, Causing Underwater Deforestation

11 July 2014

It’s what every snorkeler diving into warm equatorial water hopes to see — a prismatic array of tropical fish darting around coral reefs. But as the world’s oceans have warmed, technicolor schools of fish have become unwelcome visitors in what used to be temperate aquatic ecosystems. And as the fish invade waters closer to the poles, they are wiping out native kelp forests and seagrass meadows — radically changing life on the sea floor.

One of the most striking examples of this phenomenon, known as “tropicalization,” has taken place off the southern coast of Japan, where 40 percent of the famous kelp and algal beds have disappeared in just the last two decades. The kelp forests have taken the lucrative abalone fishing industry with them, affecting livelihoods onshore. The destruction of kelp forests has similar knock-on effects to clear-cutting a terrestrial forest.

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