I wouldn't poo poo research published in the Proceedings of the
National Academies of Science. The authors aren't amateurs.
Regards, Laurie.
http://www.pnas.org/content/early/2011/04/06/1016560108
Variability in krill biomass links harvesting and climate warming to
penguin population changes in Antarctica
• Wayne Z. Trivelpiecea,1,
• Jefferson T. Hinkea,b,
• Aileen K. Millera,
• Christian S. Reissa,
• Susan G. Trivelpiecea, and
• George M. Wattersa
+Author Affiliations
• aAntarctic Ecosystem Research Division, Southwest Fisheries Science
Center, National Marine Fisheries Service, National Oceanic and
Atmospheric Administration, La Jolla, CA, 92037; and
• bScripps Institution of Oceanography, University of California at
San Diego, La Jolla, CA 92093
•
Edited by John W. Terborgh, Duke University, Durham, NC, and approved
March 11, 2011 (received for review November 5, 2010)
Abstract
The West Antarctic Peninsula (WAP) and adjacent Scotia Sea support
abundant wildlife populations, many of which were nearly extirpated by
humans. This region is also among the fastest-warming areas on the
planet, with 5–6 °C increases in mean winter air temperatures and
associated decreases in winter sea-ice cover. These biological and
physical perturbations have affected the ecosystem profoundly. One
hypothesis guiding ecological interpretations of changes in top
predator populations in this region, the “sea-ice hypothesis,”
proposes that reductions in winter sea ice have led directly to
declines in “ice-loving” species by decreasing their winter habitat,
while populations of “ice-avoiding” species have increased. However,
30 y of field studies and recent surveys of penguins throughout the
WAP and Scotia Sea demonstrate this mechanism is not controlling
penguin populations; populations of both ice-loving Adélie and ice-
avoiding chinstrap penguins have declined significantly. We argue in
favor of an alternative, more robust hypothesis that attributes both
increases and decreases in penguin populations to changes in the
abundance of their main prey, Antarctic krill. Unlike many other
predators in this region, Adélie and chinstrap penguins were never
directly harvested by man; thus, their population trajectories track
the impacts of biological and environmental changes in this ecosystem.
Linking trends in penguin abundance with trends in krill biomass
explains why populations of Adélie and chinstrap penguins increased
after competitors (fur seals, baleen whales, and some fishes) were
nearly extirpated in the 19th to mid-20th centuries and currently are
decreasing in response to climate change.
On 13/04/2011, at 6:35 PM, Ian May wrote:
Very unlikely scenario.
Rather than negative climate impacts or human fishing scenarios
causing an 80% decline of Krill, it is more likely that the massive
expansion of whale populations are depleting the Krill biomass.
We are observing pelagic sea bird declines and there is a
correlation where whale populations are increasing.
Ian May
Laurie Knight wrote:
see http://news.mongabay.com/2011/0411-hance_penguin_krill.html
http://www.ipsnews.net/news.asp?idnews=55223
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