The latest edition of Ecology is now available. The journal includes studies on a wide variety of topics, including:
Demography of the Yellowstone Grizzly Bears
Yellowstone's grizzly bears (Ursus arctos) may seem awesomely powerful to National Park visitors, but a new study suggests they are still very threatened as a species. Written by Craig Pease (Vermont Law School) and David Mattson (US Geological Survey, Biological Resources Division), the paper analyzed nearly two decades of data on radio-collared bears in the Yellowstone ecosystem. The researchers concluded that the number of bears has changed little in the past two decades, despite intensive grizzly bear management. Bear mortality is nearly double in years when the whitebark pine crop fails, and the whitebark pine itself is in trouble, say the authors. The pine crop is now failing almost every other year, and widespread suppression of fires has also been detrimental to its health. Global warming may also pose a threat to the tree species. People also cause bear mortality in both direct and indirect ways, the researchers assert. Humans have directly caused 70-90% of all known grizzly bear deaths in the Yellowstone ecosystem since the 1970s. Whitebark pines are found at higher elevations that tend to be less used by humans. When the pine crop fails, the bears move to lower-elevation sites (which are closer to humans) to feed. "When the whitebark pine crop fails, the grizzly bear is hit with a double whammy," says Pease. "Simply being around more people increases their immediate chance of death. And by foraging closer to humans, grizzlies lose their natural wariness of people. Those bears will then have an increased risk of death forever, even in years with abundant pine seeds."
The Fern Understory as an Ecological Filter
They are seedless, flowerless and relatively small in stature, but a new study suggests that ferns can play an important role in determining the
Contact: Alison Gillespie
Ecological Society of America