KURAGE SASHIMI
By Gwynn
Guilford @sinoceros , QUARTZ
To anyone on land, climate change
can seem subtle. The sea, however, is changing alarmingly. The
latest report from the UN’s Intergovernmental Panel on Climate Change
(IPCC)—the second of three reports on the impacts of global warming—offers
the scary forecast that the hotter the planet, the higher the risk of
”abrupt and irreversible changes” (pdf, p.13) to ecosystems.
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We’ve already tipped past some of
those ”tipping points” in the oceans, though. By the middle of the
century, global warming will have thoroughly reshuffled marine ecosystems (pdf, p.16). That will leave some
areas with more sea life to catch, but will thin out the
marine populations in more temperate climes. The complex interplay of
these and other factors will invite the invasion of a few marine species,
driving others to new, less hospitable habitats—and even extinction.
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Fish don’t like it hot
Since fish are lousy at adapting to hotter
water, they simply move to where it’s cooler. This, says the IPCC report, will
hurt commercial fishing in a big way. As fishing populations in the
equatorial areas disappear, more fish and marine invertebrates will be
pushed toward the poles. That means fishing fleets will have to travel farther,
driving up costs. And some species won’t survive these strange new
habitats.
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The red and yellow areas in
the map below show where fish catches will decrease the most. Many of
these are close to shore, where commercially valuable species tend to
congregate because food is more plentiful. There are lots
of blue areas where fish populations are predicted to increase, but
they’re smaller to begin with. The IPCC is vague on whether this will
reduce the total global fish supply, but catching those fish will
certainly be harder.
This chart projects global redistribution of
around 1,000 commercial fish and invertebrate species and its impact
on annual catch weight.Intergovernmental Panel on Climate Change
Seas of acid
Fish might be crummy at adapting, but
they’re a lot better than corals—the seafloor invertebrates
that secrete the stony skeletons that form reefs. It’s hard for an
entire garden of exoskeletons to up and move when it gets too hot. The
heat will kill a lot of those corals.
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But the other big problem is the oceans’ acidity. As the oceans absorb more of the
growing levels of carbon dioxide in the atmosphere, the CO2 will
turn the water more acidic almost everywhere on the globe. That makes
it hard for corals to grow, as well as for crustaceans—e.g. crabs,
shrimp, lobsters—and mollusks to form shells, which are crucial for defending
themselves from predators and disease. And since intricate marine food
webs center around coral reefs, commercial fishing stocks will take a hit too as reefs decay.
Intergovernmental Panel on Climate Change
The spread of dead zones
Another thing the IPCC folks agree on is
that climate change is stripping the oceans of oxygen. Warmer water simply
holds less of it, making it harder for many sea creatures to survive.
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Not all creatures, though. Take, for
example, the oxygen-stripped waters of the East China and Yellow seas.
As other animals have fled or died, Nomura jellyfish—gelatinous peach-colored
behemoths the size of a large refrigerator—have thrived.
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Because it’s hard for anything else to
compete, the jellyfish never leave—as has happened off the coast of Namibia and in the Black Sea. In fact, these
“dead zones” are a prime example of the “tipping points” the IPCC
flagged—changes to the ocean that can’t be reversed.
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