Unfortunately for many whales, dolphins and other marine life, the use of underwater sonar (short for sound navigation and ranging) can lead to injury and even death. Sonar systems—first developed by the U.S. Navy to detect enemy submarines—generate slow-rolling sound waves topping out at around 235 decibels; the world"s loudest rock bands top out at only 130. These sound waves can travel for hundreds of miles under water, and can retain an intensity of 140 decibels as far as 300 miles from their source.
These rolling walls of noise are no doubt too much for some marine wildlife. While little is known about any direct physiological effects of sonar waves on marine species, evidence shows that whales will swim hundreds of miles, rapidly change their depth (sometime leading to bleeding from the eyes and ears), and even beach themselves to get away from the sounds of sonar.
In January 2005, 34 whales of three different species became stranded and died along North Carolina"s Outer Banks during nearby offshore Navy sonar training. Other sad examples around the coast of the U.S. and elsewhere abound, notably in recent years with more sonar testing going on than ever before. According to the nonprofit Natural Resources Defense Council (NRDC), which has campaigned vigorously to ban use of the technology in waters rich in marine wildlife, recent cases of whale strandings likely represent a small fraction of sonar"s toll, given that severely injured animals rarely make it to shore.
In 2003, NRDC spearheaded a successful lawsuit against the Navy to restrict the use of low-frequency sonar off the coast of California. Two years later a coalition of green groups led by NRDC and including the International Fund for Animal Welfare (IFAW), the League for Coastal Protection, Cetacean Society International, and Ocean Futures Society upped the ante, asking the federal courts to also restrict testing of more intense, harmful and far ranging mid-frequency types of sonar off Southern California"s coastline.
In filing their brief, the groups cited Navy documents which estimated that such testing would kill some 170,000 marine mammals and cause permanent injury to more than 500 whales, not to mention temporary deafness for at least 8,000 others. Coalition lawyers argued that the Navy"s testing was in violation of the National Environmental Policy Act, the Marine Mammal Protection Act and the Endangered Species Act.
Two lower courts upheld NRDC"s claims, but the Supreme Court ruled that the Navy should be allowed to continue the use of some mid-frequency sonar testing for the sake of national security. "The decision places marine mammals at greater risk of serious and needless harm," says NRDC"s Joel Reynolds.
Environmental groups are still fighting the battle against the sonar, lobbying the government to curtail testing, at least during peacetime, or to at least ramp up testing gradually to give marine wildlife a better chance to flee affected areas. "The U.S. Navy could use a number of proven methods to avoid harming whales when testing mid-frequency sonar," reports IFAW"s Fred O’Regan. "Protecting whales and preserving national security are not mutually exclusive."
The short answer is that it depends upon several variables, including the price of electricity versus gas, and the relative efficiency of the appliances involved. Typically, though, a microwave would be slightly more efficient at heating water than the flame on a gas stove, and should use up a little less energy. The reason: The microwave"s heat waves are focused on the liquid (or food) inside, not on heating the air or container around it, meaning that most if not all of the energy generated is used to make your water ready.
Given this logic, it is hard to believe that a burner element on an electric stovetop would be any better, but an analysis by Home Energy Magazine found otherwise. The magazine"s researchers discovered that an electric burner uses about 25 percent less electricity than a microwave in boiling a cup of water.
That said, the difference in energy saved by using one method over another is negligible: Choosing the most efficient process might save a heavy tea drinker a dollar or so a year. "You"d save more energy over the year by replacing one light bulb with a CFL [compact fluorescent lightbulb] or turning off the air conditioner for an hour—not an hour a day, one hour at some point over the whole year," says consumer advocate Michael Bluejay.
Although a microwave may not save much energy or money over a stove burner when heating water, it can be much more energy-efficient than a traditional full-size oven when it comes to cooking food. For starters, because their heat waves are concentrated on the food, microwaves cook and heat much faster than traditional ovens. According to the federal government"s Energy Star program, which rates appliances based on their energy-efficiency, cooking or re-heating small portions of food in the microwave can save as much as 80 percent of the energy used to cook or warm them up in the oven.
The website Treehugger.com reports that there are other things you can do to optimize your energy efficiency around the kitchen when cooking. For starters, make sure to keep the inside surfaces of your microwave oven clean so as to maximize the amount of energy reflected toward your food. On a gas stovetop, make sure the flame is fully below the cookware; likewise, on an electric stovetop, make sure the pan or kettle completely covers the heating element to minimize wasted heat. Also, use the appropriate size pan for the job at hand, as smaller pans are cheaper and more energy-efficient to heat up.
Despite these tips for cooking greener, Bluejay reiterates that most of us will hardly put a dent in our overall energy use just by choosing one appliance over another. According to his analysis, for someone who bakes three hours a week the cheapest cooking method saves only an estimated $2.06/month compared to the most expensive method.
"Focusing on cooking methods is not the way to save electricity [at home]," says Bluejay. "You should look at heating, cooling, lighting and laundry instead."