News of the Wild - impact of humans on ecology; bites by dead snakes; birds and coyotes; bird deaths caused by communication towers; birds and pesticides - Statistical Data Included

National Wildlife, Dec-Jan, 1999

Putting the Squeeze on Earth

Almost half the land on the planet has been transformed by humans-in ways that include the filling of wetlands, the conversion of prairie to farmland or the replacement of forests with cities. That conclusion comes from a recent analysis of the latest research on the subject. Biologist Jane Lubchenco of Oregon State University presented the findings to more than 4,000 scientists at the International Botanical Congress in St. Louis in August. "As inhabitants of Earth, we need to take stock of these massive changes, understand their implications and change our direction," she said. "We are currently inattentive stewards. It is in our best interests to be more fully engaged in ensuring our own health, prosperity and well-being."

Among the other statistics compiled by Lubchenco and two colleagues, Harold A. Mooney and Peter M. Vitousek of Stanford University:

* Rates of extinction are 100 to 1,000 times what they would be without human-induced changes. On land, the accelerated rates are largely caused by habitat loss and species invasions.

* The coastal areas of the world's oceans contain an estimated 50 "dead zones," areas with little or no oxygen to support life.

* About 3,000 marine species are in transit in ballast water of ships around the world, resulting in a serious invasion of various nonnative species in our waterways.

* Excess fertilizer use and burning of fossil fuel has more than doubled the amount of available nitrogen in the environment. Nitrogen is a nutrient that in large amounts can unbalance ecosystems, causing problems such as blooms of algae.

Despite all the grim findings, Lubchenco found reason for hope: "It is encouraging that there is an increasing focus on the part of the private sector, religious groups and individual citizens to take responsibility and undertake innovative action."

BITES FROM THE DEAD

Has you ever bit by a dead bee?" Walter Brennan asked in the movie To Have and Have Not. He might have asked instead about a rattlesnake. Scientists have long known that the snakes can be dangerous for a time after death, but now it appears that a significant percentage of snake bites may come from dead animals. Their strike-and-bite reflex remains active for about an hour after death. In a recent New England Journal of Medicine, two Phoenix doctors reported on people treated in their clinic for rattlesnake bites. Out of 34 pa-tients, 5 (14.7 percent) were bitten by dead snakes. Two of the snakes even had been decapitated before their victims picked up the heads, which still managed to shift or lunge to sink their fangs into the hands that held them. Oh, and about Wal-ter Brennan's advice: Bees don't bite after death, but for a short while they can sting.

Coyotes Are For the Birds

Might coyotes be good for birds? That was the question posed by two ecologists who reasoned that the presence of coyotes in a habitat might mean fewer smaller predators such as gray foxes, raccoons, oppossums and outdoor domestic cats. And that's just what Kevin Crooks of the University of California, Santa Cruz, and Michael Soule of The Wildlife Project in Colorado found when they studied habitat around San Diego. Wherever coyotes roamed, numbers of native birds rose and numbers of their smaller predators fell-because either the animals moved away or they ended up as coyote snacks.

Some of the striking statistics from the study, which was published in the journal Nature, concerned cats: Every 100 homes bordering the study's habitat fragments of about 50 acres supported an average of 35 outdoor cats. Every year each of those cats brings home an average of 15 birds, 17 lizards and 24 rodents. That means the 100 homes account for 525 known bird deaths from cats every year-and that only includes the birds the felines actually bring home.

The High Cost of Communications Towers

The next time you help create demand for communications towers-from buying a TV to ordering cellular telephone service-you might be contributing to the future deaths of migrant songbirds. Unless, that is, someone figures out how to keep the birds from smashing into the towers. That's what wildlife officials determined recently when considering both the plans for an explosion of new towers and the death toll from "towerkill." Says U.S. Fish and Wildlife biologist Albert Manville, "This is a train wreck we would prefer to avoid."

Little is known about the phenomenon, and scientists such as Cornell ornithologist Bill Evans, holding a blue grosbeak that died last spring at a tower in South Texas (left), can only guess at how many birds die at towers. The conservative count of annual towerkill deaths could be two to four million.

Towerkill takes place mostly at night during cloudy or foggy conditions. The lighting on towers, meant to warn aircraft, refracts off the droplets in the air and creates a glow around the structures. Unable to see other navigational clues in the mist, passing birds tend to linger in the lighted areas, and during migration the airspace around a fogged-in tower can become crammed with birds. In one case, as many as 10,000 Lapland longspurs died at a group of Kansas towers during a 1998 winter storm.