Perilous
Times
Sea Changes: Ocean Acidification Is Worse Than It�s Been
Ever in History!
By Bryan Walsh | @bryanrwalsh | March 2, 2012 |
Time Magazine
White coral skeleton, Cocos Island, Pacific Ocean. Such coral
bleaching events are one consequence of ocean acidification
Human beings doing unprecedented things to the Earth, which is
sort of impressive when you realize that the planet has existed
for more than 4.5 billion years. But that�s what happens when 7
billion people produce and consume more and more stuff, emitting
enormous amounts of gases like carbon dioxide and generally making
of muck of things for everyone else.
Take the oceans. Researchers already know that the seas are
becoming more acidic, thanks largely to the increase in the
atmospheric concentration of carbon. (Much of the carbon in the
air is absorbed by the oceans�think of the fizz in a soda
can�which over time makes them more acidic.) Over the last hundred
years, the ocean pH�which measures the relative acidity of a
liquid�has fallen by 0.1 unit to 8.1 That may not sound like much,
but according to a new study published in Science, it�s all but
unprecedented. Ocean acidification is now almost certainly
occurring faster than it has for at least 300 million years�and as
the rate of manmade carbon emissions increases in the future,
acidification will likely only accelerate. That will have dire
effects on corals and other ocean life that will struggle to adapt
to a marine environment that will be changing�by geological
standards at least�at breakneck pace.
Lead author Barbel Honisch, a paleoceanographer at Columbia
University, put the situation in rather grim perspective:
��� What we�re doing today really stands out. We know that life
during past ocean acidification events was not wiped out � new
species evolved to replace those that died off. But if industrial
carbon emissions continue at the current pace, we may lose
organisms we care about � coral reefs, oysters, salmon.
The Science researchers reviewed hundreds of studies of
paleoceanographic studies to try to get a consensus on how the pH
levels of the ocean has changed over time. It�s a bit like
paleontology�scientists have to look for fossils and other
physical proxies to get a sense of how changing carbon levels in
the atmosphere has affected the oceans.
The researchers found only one moment in the past when the oceans
seemed to be changing anywhere near as fast as they are today.
That was the Paleocene-Eocene Thermal Maximum (PETM), which
occurred some 56 million years ago. Back in the 1990s, scientists
excavated a layer of mud off the seafloor near Antarctica that was
traced back to that period. Over the course of 5,000 years during
the PETM, carbon levels in the atmosphere doubled for reasons
scientists still don�t know. That pushed global temperatures up by
6 C�one of the reasons why the era is called �hothouse Earth,�
while the pH of the oceans may have fallen by as much as 0.45
units, becoming significantly more acidic.
More acidic waters are bad news for sea creatures that have
carbonate shells, which can simply dissolve if pH levels fall too
low. That�s exactly what seemed to happen during the PETM. That
brown layer of mud scientists peeled off the seafloor near
Antarctica was all that was left of dissolved carbonate plankton
shells from the PETM. As many as half of all speceis of benthic
foraminifers also went extinct, which may mean that organisms
higher up on the marine chain were affected by acidification as
well.
That doesn�t bode well for our times. As rapidly as carbon
increased and the oceans became more acidic during the PETM, were
changing the climate far more quickly now�the current
acidification rate is at least 10 times faster than what happened
during the PETM. As study co-author Andy Ridgwell of Bristol
University puts it, this �raises the possibility we are entering
an unknown territory of marine ecosystem change.�
This is what�s so scary about climate change�we are altering the
planet at an incredibly rapid rate, faster than almost any
analogous historical event. Life can adapt, but the faster the
planet changes, the harder it will be for species�including us,
potentially�to keep pace. And we have a word for what happens when
species can�t keep pace with environmental change: extinction.