I remember hearing that the world's frogs were in peril. How are they doing today?
—Omar Khan, Columbus, IN
According to Harvard biology professor Jim Hanken, "Overall, the status of frogs has definitely gotten worse. The problem is more serious than we originally thought." Scientists are particularly concerned because frogs are considered a "sentinel species," meaning they serve as an indication of environmental quality.
According to the Declining Amphibian Populations Task Force (DAPTF), formed by the World Conservation Union, many species of amphibians (frogs, toads, salamanders and newts) throughout the world have experienced population declines or extinction over the last 50 years. Causes may include deforestation, draining of wetlands, ozone depletion and pollution (which may also increase rates of disease). In a few cases, as with the Costa Rican golden toad, entire species have disappeared almost overnight.
In addition to population declines is the phenomenon of amphibian deformities, such as extra eyes and legs and misshapen limbs. In the U.S., amphibian malformations have been reported in 44 states since 1996. High rates of deformities, in some cases up to 60 percent of a species, exceed what scientists generally consider natural. Research is investigating several potential causes, including parasites, contaminants and UV-B radiation.
CONTACT: Amphibian Conservation Alliance, c/o Ashoka Foundation, (703)807-5588, www.frogs.org.
Are electric bug zappers effective at killing mosquitoes?
—Cari Mariani, Charleston, SC
Summer evenings have long been accompanied by the anticipated frying frenzy of insects trapped in an electric mosquito zapper. But it may be the mosquitoes that are having the last laugh. According to a Dateline NBC investigation team, out of 10,000 carcasses recovered—one night's haul—only eight were mosquitoes.
Insect biologist Phil Pellitteri says bug zappers emit ultraviolet light to entice pests, even though mosquitoes aren't attracted to the rays, since they hone in on carbon dioxide from our breath and heat from our bodies. Approximately four million zappers are at work in the U.S. toasting nearly 71 billion innocent insects each month. The most common bugs slaughtered are beetles, moths, flies, bees, ants and wasps, many of which are beneficial for pollination and insect control.
GardenWeb suggests that the death toll can be reduced by wrapping a fine mesh screen around a bug zapper with holes that are big enough for mosquitoes to pass through but too small for larger bugs. Another option is The Mosquito Magnet, which mimics a large mammal by emitting a plume of carbon dioxide, heat and moisture. This is irresistible to the biting insects, but at $295 to $495 it's pricey.
Is it a good idea to sink man-made materials, such as old cars, into the sea for use as artificial reefs?
—Lahdan Al-Mohanadi, Doha, Qatar
Artificial reefs have been used in one form or another by fishermen to attract their quarry for some 200 years. In 1953, 250 car bodies were submerged off Alabama for use as artificial reefs. Over time, thousands of man-made materials have been tried, including bridges, pipes, boats, docks, airplanes, ballistic missiles and even specially engineered "reef balls," which are made from concrete casts. But Jack Sobel, a spokesperson for the Ocean Conservancy, says, "Artificial reefs can do as much harm as good. They are no replacement for natural reefs or for proper fisheries management, and we don't want people to view the oceans as a dumping ground for our wastes."
Advocates of man-made reefs, including many fishermen and divers, argue that reef communities can be established in areas convenient for people, such as off major cities, and some point to studies showing artificial reefs can attract as many fish as natural ones. But critics such as research biologist James Bohnsack of the University of Miami argue that artificial reefs merely concentrate fish—putting them at risk of overharvesting—instead of stimulating higher populations.
The Alabama Department of Conservation and Natural Resources, which sunk 100 obsolete combat tanks in 1994, estimates that most artificial reefs will last no longer than 50 years, meaning they could threaten fragile marine life as they break up. "There are better ways to recycle cars," concludes Sobel. "There is also no cost-effective way to remove all the hazardous materials."
CONTACT: The Ocean Conservancy, (202)429-5609, www.oceanconservancy.org.