Dear EarthTalk: I've heard about the die-off of coral reefs due to global warming. I've also read that coral reefs themselves store carbon dioxide (CO2), one of the main global warming gases. So if coral reefs are dying out, isn't that a double whammy that increases the CO2 in the atmosphere?
—Tom Ozzello, Maplewood, MN
According to marine scientists, the world's coral reefs—those underwater repositories for biodiversity that play host to some 25 percent of all marine life—are in big trouble as a result of global warming. Data collected by the international environmental group WWF (formerly World Wildlife Fund) show that 20 percent of the world's coral reefs have been effectively destroyed and show no immediate sign of recovery, while about 50 percent of remaining reefs are under imminent or long-term threat of collapse.
Most scientists now agree that global warming is not a natural phenomenon but a direct result of the continual release of excessive amounts of CO2 and other "greenhouse" gases into the atmosphere by human industrial and transportation activity. And the small but prolonged rises in ocean temperature that result cause coral colonies to expel the symbiotic food-producing algae that sustain them. This process is called "bleaching," because it turns the reefs white as they die.
But researchers working with the Coral Reef Alliance have found that while coral reefs do store CO2 as part of photosynthesis, they tend to release most of it back into the ocean (so they are not what are known as "carbon sinks"). As such, the release of CO2 from dying coral reefs is not a major concern.
Of course, the ocean itself is a large carbon sink, storing about a quarter of what would otherwise end up in the atmosphere. Landmasses (and their plants) soak up another quarter of all the CO2 emanating from the Earth's surface, while the rest rises up into the atmosphere where it can wreak havoc with our climate.
Recent findings indicate that the Antarctic Ocean is getting less efficient at storing CO2, and this raises serious questions about the ability of our oceans to handle everything we throw at them. The study's authors fear that "such weakening of one of the Earth's major carbon dioxide sinks will lead to higher levels of atmospheric carbon dioxide in the long-term."
Not everyone is forecasting gloom and doom. Some Australian researchers believe that coral reefs around the world could expand in size by up to a third due to increased ocean warming. "Our finding stands in stark contrast to previous predictions that coral reef growth will suffer large, potentially catastrophic, decreases in the future," says University of New South Wales oceanographer Ben McNeil, who led the controversial 2004 study that was published in the peer-reviewed scientific journal, Geophysical Research Letters. "Our analysis suggests that ocean warming will foster considerably faster future rates of coral reef growth that will eventually exceed pre-industrial rates by as much as 35 per cent by 2100," he adds.
In spite of such theories, the majority of marine scientists remain pessimistic about the future of coral reefs in a warmer world. One can only hope that the optimists are right.
Dear EarthTalk: Short of buying a new hybrid or other "green" car, are there ways I can make my existing vehicle more eco-friendly? I bought my car recently and am not quite ready to give it up.
—Bettie Hilliker, Lansing, MI
Choice of vehicle may well be the biggest factor in determining the environmental impact of your automobile-based travels. But a considerable amount of energy is used—and pollutants emitted—in the production of any new vehicle, including hybrids and other more fuel-efficient options. As a result, many environmentalists believe that practicing good driving habits and performing adequate maintenance on an older car are probably better options for the environment than causing the production of a new vehicle.
According to the website GreenerCars.org, there are many ways to green up one's driving habits. Obeying speed limits, utilizing cruise control and avoiding jackrabbit starts will maximize fuel economy and minimize tailpipe emissions while also preventing unnecessary wear-and-tear. Staying off roads during rush hours is also advisable, as stop-and-go driving burns excess gasoline and promotes smog. Opening vents and windows to cool off instead of using the air conditioner, an inherently inefficient appliance that consumes more fuel and leads to more emissions, is also good advice.
Drivers can also help minimize their environmental impact by keeping their cars well maintained. According to GreenerCars.org, getting regular tune-ups—where a qualified mechanic changes fluids and checks for and corrects problems such as worn spark plugs, under inflated tires, dragging brakes, misaligned wheels and clogged filters—can significantly improve fuel economy and minimize harmful emissions. GreenerCars.org also recommends seeking out low-rolling-resistance (LRR) replacement tires, which are specifically designed to improve a vehicle's fuel economy, when the original ones wear out.
Beyond regular maintenance, a handful of small companies now sell green-friendly fuel additives that purport to increase fuel efficiency while reducing emissions. Such products—including Bluestar Environmental's Omstar D-1280X gas additive and Suntec Bio-Energy's diesel additive—are normally targeted at fleets of vehicles, but individuals are free to use them as well. Owners beware, though: Use of such products could invalidate automakers" warranties, so read the fine print in your owner's manual before pouring anything out-of-the-ordinary into your fuel tank.
Of course, getting out of your car altogether—or most of the time—is a far greener choice than driving even a well-maintained new or old car conscientiously. Some employers now offer federally-subsidized "commuter choice" incentives whereby workers can derive financial benefits by telecommuting (working from home), or by walking, biking, using public transit or carpooling to and from the office.
Another option is to join a car sharing service like Zipcar or Flexcar, whereby you pay a modest monthly membership fee and can then rent cars parked nearby by the hour only when needed. The companies operate on both U.S. coasts, as well as in major Midwestern and Canadian cities.