Health & Science

The bloody fang and the food chain

The disappearance of predators like wolves, lions, and sharks is having a disastrous impact on global ecosystems, scientists say. Until now, conservation efforts have largely focused on saving entire habitats, but a new international survey shows that in terms of their ecological impact, “all species aren’t created equal,” Peter Kareiva, chief scientist at the Nature Conservancy, tells DiscoveryNews.com. “You may hate wolves,” says study co-author Ellen K. Pikitch of Stony Brook University. “But without them, the land changes.” The decimation of North America’s wolf population, she says, has not only allowed elk and deer to suppress willows and other trees, but also to more readily carry ticks—and the Lyme disease they spread—into human contact. On the Atlantic coast, fewer sharks mean more cownose rays, which in turn have been able to feast too freely on the now-threatened Chesapeake Bay oyster. Kareiva says the findings suggest that instead of “blindly protecting all species,” we should focus on the “apex consumers” at the top of the food chain, which are currently disappearing even faster than other animals because they need more space to roam and more time to reproduce.

Earth’s source of inner heat

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Beneath its surface, our planet continually generates about 44 trillion watts of power, roughly three times what humans use worldwide. At least half of it, Japanese scientists have found, stems from the continual decay of radioactive isotopes of uranium, thorium, and potassium in the earth’s crust and mantle. The rest of it, emanating from the earth’s core, is a remnant of the intense collision of gas and dust that created the planet in the first place, some 4.5 billion years ago. Distinguishing the sources of the earth’s heat is “a very important issue in geophysics,” Itaru Shimizu, a physicist at Tohoku University in Sendai, Japan, tells OurAmazingPlanet.com. The new study suggests that radioactive decay, rather than primordial heat from the core, is more likely to “drive plate tectonics and geophysical activity,” such as volcanoes and earthquakes, which are essentially how the earth vents and controls its heat output. If scientists could figure out how to harness a fraction of that energy, humans’ power needs would be covered for the life of the planet.

For baboons, beta is better

It’s not easy being at the top—at least if you’re a baboon. A new study shows that alpha male baboons face the same high levels of anxiety as the lowest troop members do, and far more than beta males. “That was surprising, because in baboon society, being the boss is great,” lead author Laurence Gesquiere, a Princeton biologist, tells ABCNews.com. The payoffs: better food and more-desirable females. But by observing baboons’ behavior and analyzing their droppings in Kenya over nine years, Gesquiere and colleagues found that alpha males spent 17 percent more time fighting off challengers and guarding their females than their beta lieutenants did, and they had 10 percent higher levels of the stress hormone glucocorticoid. In the long term, that extra glucocorticoid leaves the alphas subject to diseases and decreased fertility, says co-author Jeanne Altmann. That may explain why alpha baboons host more parasites than their subordinates—and need nearly 30 percent more mating time to achieve only somewhat better reproductive results.

Preventing Alzheimer’s

There’s no cure in sight for the 5 million Americans suffering from Alzheimer’s disease. But a new study has found that it’s possible to greatly reduce your chances of developing the disease by lifestyle choices. The study, by the Mayo Clinic, found that seven known risk factors contribute to up to half of Alzheimer’s cases worldwide. For Americans, the single biggest risk factor is physical inactivity, which the study linked to 21 percent of U.S. Alzheimer’s cases. Depression accounts for another 15 percent, and smoking for 11 percent. Globally, lack of education is the greatest risk factor, with a link to 19 percent of cases; scientists say minds that are not active and engaged in learning are more susceptible to the disease. The findings contradict the widespread belief that Alzheimer’s is a predetermined genetic fate. Worldwide dementia rates are expected to triple over the next 40 years, as seniors make up an increasingly large proportion of the global population. Researcher Deborah Barnes of the University of California at San Francisco tells the Associated Press that the study provides hope that we can slow “the epidemic that is coming our way.”