Dear EarthTalk: Recent NASA photos showed the opening of the Northwest Passage and that a third of the Arctic's sea ice has melted in recent years. Are sea levels already starting to rise accordingly, and if so what effects is this having?
—Dudley Robinson, Ireland
Researchers were astounded when, in the fall of 2007, they discovered that the year-round ice pack in the Arctic Ocean had lost some 20 percent of its mass in just two years, setting a new record low since satellite imagery began documenting the terrain in 1978. Without action to stave off climate change, some scientists believe that, at that rate, all of the year-round ice in the Arctic could be gone by as early as 2030.
This massive reduction has allowed an ice-free shipping lane to open through the fabled Northwest Passage along northern Canada, Alaska and Greenland. While the shipping industry—which now has easy northern access between the Atlantic and Pacific oceans—may be cheering this "natural" development, scientists worry about the impact of the resulting rise in sea levels around the world.
With about a third of the world's population—and 25 percent of Americans—living within 300 feet of an ocean coastline, sea level rise is a big deal. According to the Intergovernmental Panel on Climate Change, made up of leading climate scientists, sea levels have risen some 3.1 millimeters per year since 1993.
The World Wildlife Fund (WWF) reports that low-lying island nations, especially in equatorial regions, have been hardest hit by this phenomenon, and some are threatened with total disappearance. Rising seas have already swallowed up two uninhabited islands in the Central Pacific. On Samoa, thousands of residents have moved to higher ground as shorelines have retreated by as much as 160 feet. And islanders on Tuvalu are scrambling to find new homes as salt water intrusion has made their groundwater undrinkable while increasingly strong hurricanes and ocean swells have devastated shoreline structures.
WWF says that rising seas throughout tropical and sub-tropical regions of the world have inundated coastal ecosystems, decimating local plant and wildlife populations. In Bangladesh and Thailand, coastal mangrove forests—important buffers against storms and tidal waves—are giving way to ocean water.
Unfortunately, even if we curb global warming emissions today, these problems are likely to get worse before they get better. According to marine geophysicist Robin Bell of Columbia University's Earth Institute, sea levels rise by about 1/16" for every 150 cubic miles of ice that melts off one of the poles.
"That may not sound like a lot, but consider the volume of ice now locked up in the planet's three greatest ice sheets," she writes in a recent issue of Scientific American. "If the West Antarctic ice sheet were to disappear, sea level would rise almost 19 feet; the ice in the Greenland ice sheet could add 24 feet to that; and the East Antarctic ice sheet could add yet another 170 feet to the level of the world's oceans: more than 213 feet in all." Bell underscores the severity of the situation by pointing out that the 150-foot tall Statue of Liberty could be completely submerged within a matter of decades.
Dear EarthTalk: What's available now in lawnmowers that are easier on the environment? My yard is too big for one of those "reel" mowers, and I'm no longer a spring chicken, so I have to buy something that runs on more than human power. What's out there?
—Joel Klein, Albany, NY
According to the U.S. Environmental Protection Agency (EPA), traditional gas-powered lawnmowers are a public nuisance to say the least. Using one of them for an hour generates as many volatile organic compounds—dangerous airborne pollutants known to exacerbate human respiratory and cardiovascular problems—as driving a typical car for 350 miles. The EPA estimates that, with some 54 million Americans mowing their lawns on a weekly basis, gas lawnmower emissions account for as much as five percent of the nation's total air pollution. Beyond that, homeowners spill some 17 million gallons of gasoline every year just refueling their lawnmowers.
So what's a green-minded property owner to do about keeping the grass down? Go electric, of course!
Electric mowers, which either plug into a wall outlet via a long cord or run on batteries charged up from the grid, create no exhaust emissions and run much cleaner than their gas-powered counterparts. They also need less maintenance, with no spark plugs or belts to worry about, and are easier to use, as they tend to be smaller and come with push-button starters. The icing on the cake might be the fact that electric mowers are cheaper to run, using about as much electricity as an ordinary toaster. Most electric mower owners spend about $5 a year on electricity to keep their grass trimmed just right. The non-profit Electric Power Research Institute reports that replacing half of the 1.3 million or so gas mowers in the U.S. with electric models would save the equivalent amount of emissions of taking two million cars off the road.
But going electric has some minor trade-offs. Electric mowers tend to cost up to $150 more than their gas-powered counterparts, and the plug-in varieties can only go 100 feet from the closest outlet without an extension cord. And the cordless models last only 30-60 minutes on a charge, depending on battery size and type, though that's plenty sufficient for the average lawn (just remember to re-charge it in time for the next mow).
And, of course, just because electric mowers don't consume fossil fuels or spew emissions directly doesn't mean they are totally green-friendly. Most people derive their household electricity from coal-fired power plants, the dirtiest of all energy sources. Of course, running an electric mower on electricity generated from clean and renewable sources (solar, wind or hydro power) would be the greenest of all possibilities, and those days may be upon us soon.
For those ready to take the electric mower plunge, the Greener Choices website, a project of Consumer Reports, gives high marks to Black & Decker's corded ($230) and cordless ($400) models for their efficiency, reliability and ease-of-use. Corded models from Worx and Homelite (both around $200) also fared well, along with cordless offerings from Craftsman, Homelite, Remington and Neuton ($300-450).