Saturday, January 1, 2011

Hyenas should live in Paris

I just came across an interesting paper in Quaternary Science Reviews that also got some international press coverage when it came out last September, though I missed it at the time (this article is from Wired: http://www.wired.com/wiredscience/2010/09/what-killed-europes-hyenas/)

The main finding of the study was that spotted hyenas, the giggling hunter/scavengers that we normally think of as living in tropical Africa, also lived in much of Europe for the last million years or more, and they only vanished from those former haunts around the end of the last ice age when the mammoths and wooly rhinos that they coexisted with also died out. Their European range stretched from Spain to the Urals, meaning that they did well in seasonally chilly environments as well as in hot ones.  In other words, hyenas "should" still live in Europe.



Photo here by Silvain de Munck; Original article = Varela, S., Lobo, J., Rodríguez, J., & Batra, P. 2010. Were the Late Pleistocene climatic changes responsible for the disappearance of the European spotted hyena populations? Hindcasting a species geographic distribution across time. Quaternary Science Reviews, 29: 2027-2035

Two things come to mind, the first one being that this is just one more example of humans being implicated in mass extinctions.  Some scientists still argue that the charismatic "ice age" mammals must have died out because of climate change, but as I mentioned in an earlier post and as these authors clearly demonstrate, the weight of evidence strongly suggests otherwise.  If the end of the last ice age killed off Europe's hyenas, then how come they lasted at least a million years under similar conditions, and why do they still live in tropical Africa today?

But the second realization may be more important for modern times. As the authors point out, we tend to associate species with particular environments on the basis of where we find them today, and as we try to anticipate the effects of future climate change on animals and plants we may be misled if we forget that today's home ranges are not normal, either. 

Human activity has radically re-sculpted the distributions of countless species in recent centuries to millennia, so how can we be sure where species really COULD live if given the opportunity? Are some species actually more geographically adaptable than we think and, if so, which ones?

We run into this same kind of problem when some people claim that global warming will allow malaria to invade North America - without realizing that it's actually already native to this continent but has been extirpated by massive mosquito-control efforts (pesticides, window screens, etc.).

We also encounter it when some people present computerized predictions about the effects of future warming on North America trees and birds, such as the much-cited, interactive atlases offered online by the USDA Forest Service (http://www.nrs.fs.fed.us/atlas/).  Here, for example, is where sugar maples live today (left) and where they might prefer to live in a warmer future (right).



Such projections can seem impressive because they're based on "the latest super-computer models" and they make colorful, detailed maps of where sugar maples or loons supposedly may or may not exist in a warmer future.  But they all suffer from a core problem that's difficult to remedy in a world that's so heavily human-impacted; the supposed "normal" ranges are largely based on today's patchwork remnant of former ranges that don't necessarily reflect where species would live if our forebears hadn't shot/lumbered/burned/infected so many of their ancestors.

In the long run, the only thing we can be sure of in this regard is that future climates will differ from those of today (mostly being warmer than now for the next tens of thousands of years), and that human activity will continue to play a hugely powerful role in determining what lives where on the Future Earth.

Welcome, for better or for worse, to the "Anthropocene" - the Age of Humans.

And "Vive la hyène!"

3 comments:

  1. Fascinating stuff, Curt. Thanks for re-opening my eyes to the bigger picture. Looking forward to your book.

    ReplyDelete
  2. So great to have these really interesting posts to read! More! :-)

    ReplyDelete
  3. Notice the http title to my blog.

    http://the end of the anthropocene epoch. blogspot.com/

    This was a former title.

    ReplyDelete