A new study claims that Australia’s Great Barrier Reef, the
world’s largest coral reef system, has lost over half of its coral cover in
just 27 years. Measuring coral cover from 1985 to 2012, researchers are saying
that the coral cover has gone from 28% to a stunning 13.8%.
What’s causing such a massive loss of coral cover?
Researchers say it’s a combination of three main factors: storms and cyclones,
Crown of Thorns starfish, and bleaching due to climate change. And if it
doesn’t stop, it will mean a devastating habitat loss for thousands of species.
About 48% of the damage can be attributed to 34 cyclones
that have hit the reef since 1985. Another 42% of the damage is from Crown of
Thorns starfish, which feed on the coral. The last 10% of the damage is due to
coral bleaching, which is caused by rising ocean water temperature and acidity.
John Gunn of the Australian Institute of Marine Science
calls the situation “grim,” and says that if things remain the same, the next
ten years will see a loss of another 50% from the Great Barrier Reef.
Both storms and coral bleaching are incredibly difficult to
impact, so for now the short-term focus is on the starfish. Improved water
quality and reduction of algae that the starfish larvae feed on will be
essential in controlling the outbreaks.
Recovery is possible, according to the co-author of the
study, Hugh Sweatman. Unfortunately, recovery generally takes from 10-20 years.
But because storms, starfish, and bleaching have been fairly frequent in
occurrence, it’s kept the reef from recovering fully.
The next 10 years will be telling. The Australian government
is currently making significant financial contributions to solve the reef
crisis, but only time will tell whether the efforts being made will lead to a
recovery or further devastation.
Shrinking Fish
A new study on the effects of global warming warns that
rising water temperatures could cause fish to shrink in size from anywhere
between 14% and 24%. Previous research has suggested that the continued
emissions of greenhouse gasses could have a negative impact on reproduction
rates of fish as well.
The research was conducted by modeling rising temperatures
with about 600 species from 2001-2050. The projections used small changes in
temperature and came up with some surprisingly large results.
As ocean waters rise, so does the body temperature of fish.
With this comes a higher metabolic rate and therefore a larger demand for
oxygen to grow and maintain a larger size. Because the oxygen levels in the
water will no longer be able to meet the needs of a larger sized fish, growth
will stop at a smaller body size.
The research also suggests that these changes will also
affect movement patterns of fish, and predicts that most fish will start moving
toward the poles. We could start seeing tropical fish in northern waters,
according to Dr. William Cheung, lead author of the study.
The largest reduction in size is predicted for the Indian
and Atlantic oceans, and some are saying the study may have been conservative
in its estimates. It’s possible even greater size changes are in store.
The study recognizes its limitations—the major one being the
uncertainty of predicting climate—and Dr. Cheung says that more research is
needed. What would other biological side effects of a size change be? It’s
possible that not just reproduction is on the line, but also a number of other
consequences, such as the resilience of fish to natural and non-natural
environmental factors.
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