26 July 2007

An ocean of trouble

While humans are responsible for the majority of the observed climate change to date, we are not the only ones who are at risk. The entire biosphere is affected and a seemingly isolated impact can come back to have a potentially large effect on humanity. These sorts of effects often follow the so-called Law of Unintended Consequences. Sadly, many impacts of this type are beginning to be observed in the oceans, which is experiencing a warming and an increase in sea levels due to climate change, as well as being overfished and heavily polluted. Below are links to recent news items describing impacts on marine fauna.

British scientists have determined Antarctic limpets might not be able to survive global warming.

...striped bass -- one of the bay's most beloved fish for food and sport -- as a creature under pressure from the heat. Foundation officials said the bass, also called rockfish, cannot tolerate water temperatures much above 76 degrees.

But when the water near the surface gets that hot, they sometimes cannot dive to cooler water because, as a result of the bay's existing pollution problems, there is often little oxygen at lower depths.

Finally, there's global warming's most direct effect – more heat.

Turtles lack sex chromosomes. Their genes do not directly determine whether a hatchling comes out male or female. Instead, buried eggs take their cue from the ambient temperature. For leatherbacks, temperatures below 29.4 degrees C (85 degrees F.) produce a clutch that is mostly male; above that, it's mostly female. With a mere 2 degree C (3.6 degrees F.) increase, a nest will produce all females. A few degrees higher yet, and the "boiled" eggs don't hatch at all.

In order to maintain a viable breeding population, a cool, male-producing year has to come at least once every five to 10 years, says James Spotila, a professor of environmental science at Drexel University in Philadelphia. If male years begin to come only every 20 years because of climate change, the turtle could become extinct.

...jellyfish are thriving because of warming oceans and over-fishing, which is eliminating their predators and competitors. In the Black Sea, now thought to have passed an ecological tipping point, one sample found that 90 per cent of the biomass was jellyfish...

There is a link between these last two stories, and an indicator of the linkage of effects noted above. Apparently seas turtles are one of the few creatures that prey on jellyfish. Fewer sea turtles mean more jellyfish. Jellyfish are more than an inconvenience to beach-goers. Rather, they prey on the young of fish consumed by people. Hence, more jellyfish means fewer fish that we eat and a potential reduction in the food supply. An example of how anthropogenic climate change threatens us at many different levels, not simply more extreme weather.

We have a relatively poor understanding of how the various components of the biosphere interact. It is past time to stop our uncontrolled experiment in atmospheric carbon dioxide enhancement and live sustainably, in harmony with the natural world.

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