of corals, which were attached to little tiles, would be periodically lifted
out of the water and weighed. If the colony was putting on weight, it
would show that it was growing—adding more mass through calcification.
The experiment took more than three years to complete and yielded more
than a thousand measurements. It revealed a more or less linear
relationship between the growth rate of the corals and the saturation
state of the water. Corals grew fastest at an aragonite saturation state of
five, slower at four, and still slower at three. At a level of two, they
basically quit building, like frustrated contractors throwing up their
hands. In the artificial world of Biosphere 2, the implications of this
discovery were interesting. In the real world—Biosphere 1—they were
rather more worrisome.
Prior to the industrial revolution, all of the world’s major reefs could
be found in water with an aragonite saturation state between four and
five. Today, there’s almost no place left on the planet where the
saturation state is above four, and if current emissions trends continue,
by 2060 there will be no regions left above 3.5. By 2100, none will remain
above three. As saturation levels fall, the energy required for calcification
will increase, and calcification rates will decline. Eventually, saturation
levels may drop so low that corals quit calcifying altogether, but long
before that point, they will be in trouble. This is because out in the real
world, reefs are constantly being eaten away at by fish and sea urchins
and burrowing worms. They are also being battered by waves and storms,
like the one that created One Tree. Thus, just to hold their own, reefs
must always be growing.
“It’s like a tree with bugs,” Langdon once told me. “It needs to grow
pretty quickly just to stay even.”
Langdon published his results in 2000. At that point many marine
biologists were skeptical, in no small part, it seems, because of his
association with the discredited Biosphere project. Langdon spent
another two years redoing his experiments, this time with even tighter
controls. The findings were the same. In the meantime, other researchers
tuis.
(Tuis.)
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