Sunday, August 21, 2005
Whose Timeline is it Anyway?
How do you decide whether someting is native or not native? A common cutoff used by ecologists in the U.S. has always been the arrival of Columbus. The 16th century benchmark is also used in Europe, but in a slightly different way: archaeophytes are species introduced before the year 1500, neophytes are those introduced after.
Now some scientists are going even further back in time to place their benchmark. It has been 13,000 years since large predators and herbivores (mega-megafauna?) roamed North America. So long ago that it is impossible for most humans to imagine, but the scientists have determined this to be the time at which we had the right mix of species. Unfortunately, many of these species are extinct, so the proposal is to "re-wild" the continent with their African and Asian counterparts. Read a summary from Scientific American, or read the full commentary from Donlan et al. in the journal Nature.
Could introducing top-level predators like lions and cheetahs, and large herbivores like camels and tortoises, really restore the health of American ecosystems? None of you reading this will be around long enough to find out. The real questions you should be thinking about are:
- How do we determine the "health" of an ecosystem?
- How do scientists currently rate the health of ecosystems where these mega-megafauna currently live?
- What is the risk of re-wilding introducing a new pathogen that will negatively impact native species? The Nature commentary notes this is a real risk that must be evaluated before proceeding. It also notes that there are already over 75,000 large introduced mammals (most from Africa) currently residing at ranches in Texas!
- Where does this stop? Should Friends for Floyd get their way and "re-"introduce pink flamingos to Utah? Should we start reforesting land according to what species are found in pollen cores? What about the dinosaurs? When the heck are we going to start cloning dinosaurs???
I don't have the answers here - feel free to comment if you think you do.
P.S. - Faithful readers, you can now stop emailing me about blogging this story. I tried to ignore it, but y'all wouldn't let me :-).
Hmmm... lots of food for thought!
Here in the UK, the indigenous vs. introduced debate gets more and more complex every year. The view that indigenous species arrived here without assistance from humans is a bit simplistic. Some species that we think of as introduced would probably have made it to the British Isles without human assistance anyway. We're only 22 miles from continental Europe after all.
Here's something that's always puzzled me: at what point do humans cease to be regarded as a natural component of an ecosystem?
The best part of this is that the dude responsible, Josh Donlan, has done work related to the control of invasive species. See "Research for Requiems: The Need for More Collaborative Action in Eradication of Invasive Species". I guess it's like Roger B. pointed out: in Donlan's mind, it's all about how we define "nonindigenous".
How do you determine the health of an ecosystem?
If you use established acceptable levels of diveristy taking latitude, climate, and ecotype into consideration, then I think that biodiversity is a good way to determine the health of an ecosystem. But this is the sort of question that would generate hours of conservation in one of my graduate ecology classes.
However, I strongly believe the scientists that published this article in Nature are media-hungry lunatics. I believe in Shifting baseline syndrom, but pleistocene megafauna? Get real.
Ah, but don't forget the most important question of all: "Dude, wouldn't it be totally awesome if there were, like, elephants and giant turtles and lions and stuff wandering around all over the Great Plains?" Anecdotal evidence suggests that it would indeed rock remarkably hard.
No apologies necessary Matt. Now put down your hunter's rifle and step away from that kitty cat :-P.
I can't officially speak for the land trust I volunteer for in the area west of Houston, but we have a goal of protecting 50,000 acres of coastal prairie. The trust is not going to attempt to restore the tallgrass prairie that prevailed around here till colonial times. The trust management sees the current ecology as it developed with ranching and rice farmingais quite intersting and diverse as it exists now. To gain landowner cooperation in giving us a good deal on making fee purchases or purchases of conservation easements, we often lease the land back for agriculture and permit hunting to continue as it has since the nineteenth century in these farmed areas. The prairie supports a wonderful variety of migrating birds in the fall and winter, too. Actors that maintained the tallgrass prairie, namely, wildfires, buffalo and American Indians, are gone. And just try to get a major burn permit in the Hosuton -Harris County nonattainment area or nearby to it. I am concerned that the plans to reintroduce a few emblematic species of the Plio-Pleistocene will founder on the same problems: the Great Plains world has moved on.
If you want a good example of these abrupt reintroductions, look at the early history of reintroducing African-American slaves to Africa in the artificial nation of Liberia. Many of the people sent back had been born from ancestors who had been in the USA for generations. They had lost their immunity to the local African pathogens. I am sure many of their ancestors had not even come from the immediate area set aside for the Liberian experiment. Many of the transplants died: Africa was not home anymore, and for many, Liberia was no even their ancestral home territory. Ther will be unanticipated problems if such reintroductions of African fauna occur over large geographical areas. The game ranches down here in Texas at least have managers and vets and the like and a limited population to look after. It all sounds like a bad idea to me.
Americans freak out about the predators like wolves and bears we already have. Who really thinks the cattle ranchers are going to embrace lions on the Great Plains?
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