Global Greenhouse Goads Plants

The world has gotten greener, thanks to global warming. Balmier temperatures have boosted plant mass by 6 percent over the past 20 years, according to a new study published in the journal Science.

In the study, scientists analyzed satellite and ground images to determine the amount of plant tissue present. They found that the tropics and high latitudes of the Northern Hemisphere got 80 percent of the extra growth. The Amazon rainforest saw more than half of all plant biomass increases, despite heavy logging around its perimeters. Canada and India also enjoyed significant gains in plant productivity.

The recent 9.3 percent rise in greenhouse gases probably isn't responsible for all of this plant progress, nor are researchers sure how much of this increase to attribute to human activities versus natural climate patterns. But the past two decades have been the warmest in recorded history, bringing more of the heat, light, water, and carbon dioxide plants need to thrive. The study was funded by NASA and the U.S. Department of Energy.

Dragonflies Can Appear Still While Flying

Hunting dragonflies can make themselves appear still when they are actually flying. A dragonfly stalking prey can move in such a way that it always remains in the same spot on the animal's retina. From the perspective of the hunted, the dragonfly appears stationary. Because a stationary animal is not perceived as a threat, the victim doesn't become alarmed.

Aikiko Mizutani of the Australian National University in Canberra discovered this talent while filming male dragonflies locked in territorial dogfights. Using cameras that can pinpoint an object's position in three dimensions, he found that each dragonfly followed a flight path that would make it appear stationary to its rival.

Scientists don't yet know how dragonflies make such sophisticated flight plans, though they know the insects must somehow be able to both sense their position in space and control their flight very precisely. The research was reported in the journal Nature.

Boys Demand More Food Before Birth

Women expecting baby boys eat more than women who will give birth to girls. Reported in the British Medical Journal, the discovery suggests male fetuses affect their mothers' appetites through chemical signals. It may also explain why baby boys, on average, are born 3.5 ounces heavier than girls.

Researchers from the Harvard School of Public Health in Boston, Mass., and the Karolinska Institute in Stockholm, Sweden, tracked the food intake of 244 American women during their 26th week of pregnancy. They also tabulated how much weight the women gained during pregnancy.

The women pregnant with boys consumed about 200 more calories per day, or 10 percent more total food, than women pregnant with girls. Yet the mothers-to-be of boys didn't gain any more weight, suggesting that the extra food was going toward infant development. The findings indicate that male fetuses are somehow communicating their optimal calorie needs to their mothers, possibly through the testosterone they make while still in the womb.

Male Bobcats Seduce Canadian Lynx

Bobcats from Minnesota are breeding with endangered Canada lynx, according to genetic tests. Suspicion first arose when wildlife biologist Ed Lindquist of Minnesota saw an animal along the highway that resembled both a lynx and a bobcat. Lindquist brought the matter to Michael Schwartz of the U.S. Forest Service Rocky Mountain Research Station, who created a DNA test to detect a lynx-bobcat hybrid.

Analysis of previously collected hair and tissue samples from 19 animals turned up three lynx-bobcat hybrids. Curiously, all three are the result of a male bobcat mating with a female lynx. Because the hybrids haven't been captured, its unknown if they are sterile. Despite nationwide DNA tests, the two species do not seem to be mixing outside of Minnesota.

Nonetheless, scientists are already beginning to consider why the animals are hybridizing, what impact interbreeding may have on remaining lynx populations, and how mixing could affect future lynx recovery efforts. The Canada lynx is a federally threatened species, meaning it is likely to become endangered in the foreseeable future in all or a significant portion of its range. The study was released by the U.S. Fish and Wildlife Service.

Woolly Mammoths Survived Ice Age on a Grass Diet

The woolly mammoths, horses, and bison who endured the last Ice Age did so entirely on a diet of grasses and prairie sage, Canadian scientists say. The landmass they inhabited, an area known as Beringia which stretched between Canada and Siberia, is now submerged beneath the Bering Sea. This has made analyzing the region's fossils difficult.

However, Grant Zasula of Simon Fraser University in Burnaby and colleagues contend fossils in Canada's Yukon Territory are similar to what might have lived in easternmost Beringia. The scientists examined Ice Age plant fossils, including a rodent nest and the stomach contents of an extinct horse. The grass and sage species present suggest the region was a year-round dry grassland, able to feed large populations of mammals through the coldest periods of the Ice Age.

The discovery, reported in the journal Nature, is particularly interesting because no equivalent to these grasslands exist in the present-day Arctic: Modern tundra does not produce nearly enough vegetation to support an extensive population of large mammals. Rather, this "mammoth-steppe" ecosystem would have looked more like the warmer, present-day subarctic zone.

Related Links

Global Greenhouse Goads Plants: CNN
Dragonflies Can Appear Still While Flying: Nature Science Update / MSNBC (Reuters)
Boys Demand More Food Before Birth: CBS (Associated Press) / The Herald
Male Bobcats Seduce Canadian Lynx: U.S. Fish and Wildlife Service / Minneapolis Star Tribune
Woolly Mammoths Survived Ice Age on a Grass Diet: CNN (Reuters) / Canadian Broadcasting Company