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
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Contact: Alison Gillespie
alison@esa.org
202-416-6181
Ecological Society of America
7-Apr-1999