Over at Aeon, the great Stewart Brand has a very nice piece on extinction that parallels what I have written on this blog.
Brand writes:
Many now assume that we are in the midst of a human-caused ‘Sixth Mass Extinction’ to rival the one that killed off the dinosaurs 66 million years ago. But we’re not. The five historic mass extinctions eliminated 70 per cent or more of all species in a relatively short time. That is not going on now. ‘If all currently threatened species were to go extinct in a few centuries and that rate continued,’ began a recent Nature magazine introduction to a survey of wildlife losses, ‘the sixth mass extinction could come in a couple of centuries or a few millennia.’
The range of dates in that statement reflects profound uncertainty about the current rate of extinction. Estimates vary a hundred-fold – from 0.01 per cent to 1 per cent of species being lost per decade. The phrase ‘all currently threatened species’ comes from the indispensable IUCN (International Union for Conservation of Nature), which maintains the Red List of endangered species. Its most recent report shows that of the 1.5 million identified species, and 76,199 studied by IUCN scientists, some 23,214 are deemed threatened with extinction. So, if all of those went extinct in the next few centuries, and the rate of extinction that killed them kept right on for hundreds or thousands of years more, then we might be at the beginning of a human-caused Sixth Mass Extinction.
An all-too-standard case of extinction mislabeling occurred this January on the front page of The New York Times Magazine. ‘Ocean Life Faces Mass Extinction, Broad Study Shows,’ read the headline. But the article by Carl Zimmer described no such thing. Instead it was a relatively good-news piece pointing out that while much of sea life is in trouble, it is far less so than continental wildlife, and there is time to avoid the mistakes made on land. The article noted that, in the centuries since 1500, some 514 species have gone extinct on land but only 15 in the oceans, and none at all in the past 50 years....
The best summation I have seen of the current situation comes from John C Briggs, biogeographer at the University of South Florida, in a letter to Science magazine last November:
Most extinctions have occurred on oceanic islands or in restricted freshwater locations, with very few occurring on Earth’s continents or in the oceans. The world’s greatest conservation problem is not species extinction, but rather the precarious state of thousands of populations that are the remnants of once widespread and productive species.
...The frightening extinction statistics that we hear are largely an island story, and largely a story of the past, because most island species that were especially vulnerable to extinction are already gone...
But the main news from ocean islands is that new methods have been found to protect the vulnerable endemic species from their worst threat, the invasive predators, thus dramatically lowering the extinction rate for the future....
More than 800 islands worldwide have now been cleansed of their worst extinction threat, with more coming....
Throughout 3.8 billion years of evolution on Earth, the inexorable trend has been toward an ever greater variety of species. With the past two mass extinction events there were soon many more species alive after each catastrophe than there were before it....
Part of the problem is in the way we classify degrees of endangerment. The Red List categories read, in order: extinct; extinct in the wild; critically endangered; endangered; vulnerable (that goes for Atlantic cod); near-threatened; and least concern. ‘Least concern’ is strange language. What it means is ‘doing fine’. It applies to most of the 76,000 species researched by the IUCN, most of the 1.5 million species so far discovered, and most of the estimated 4 million or so species yet to be discovered. In the medical analogy, labelling a healthy species as ‘least concern’ is like labelling every healthy person ‘not dead yet’. It’s true, but what a way to think....
Of the several million species yet to be discovered, there is a reasonable argument that many are very rare and thus extra-vulnerable to extinction, but the common statement that ‘Species are going extinct faster than we can discover them’ does not hold up to scrutiny. According to the paper in Science ‘Can We Name Earth’s Species Before They Go Extinct?’ (2013) by the marine ecologist Mark J Costello at the University of Auckland and colleagues, the rate of documenting new species was 17,500 a year over the past decade, rising above 18,000 a year since 2006. There are ever more professional taxonomists (currently about 47,000) doing the work, along with burgeoning crowds of amateur taxonomists newly enabled by the internet. With a realistic current extinction rate of less than 1 per cent of species per decade and a discovery rate of something like 3 per cent a decade, the authors conclude: ‘the rate of species description greatly outpaces extinction rates’.
7 comments:
I agree that the current situation may be exaggerated on some counts. Nevertheless, humans driving other species to extinction is a serious problem, and it has been happening for a long time. Ever since we left Africa some 50,000 years ago, we have been overhunting animals and altering their habitat, tipping them over the edge into extinction. This is how we lost horses, camels, mammoths, mastodons, ground sloths, giant armadillos, and the predators that relied on them here in the Americas some 11,000 years ago. The African fauna remained more or less intact, and parts of Asia still remain diverse, but other animals in Eurasia and Australia were likewise driven to extinction by humans. We must curb our powers of destruction if we're ever to enjoy a diverse, functional biosphere.
Interesting, so I can put cod back on the menu?
In the UK, we're currently concerned about bees which are certainly necessary beasts.
http://bumblebeeconservation.org/about-bees
The point Steward is making -- and one that I have made before -- is that you can hammer numbers down quite a lot, but extinction is relatively rare in the modern world in part BECAUSE we have feedback loops.
The history of the U.S. is a good example. We shot out everything east of the Mississippi between 1850 and 1900. There were no beaver. Turkey were reduced to a small population in Arkansas. We had virtually no deer in Virginia. Wolves were gone and bison down to a few hundred. There were no elk east of the Missippi. The Canada Goose was thought to be extinct. Today, we have more deer and turkey than we did in pre-Columbian time, so many beaver it is illegal to move them, so many coyote we have a bounty on them in my state, and Canada Geese are everywhere. Elk have have been reintroduced in the East and are thriving, and bison herds are so large the meat is sold in the supermarket. We did this through intelligent conservation.
There is no intelligent conservation in the ocean, but the seas and oceans are so vast that actually making a species extinct is hard. That said, Cod population have been decimated, as have most commercial fish stocks around the world, which is why I do not eat fish at all. Atlantic Cod are a pretty slow growing fish, but limits and moratoriums should see their number bounce up over the next 20 years or so. Mother Nature will get up and dance if we will only take our boot off her neck!
http://www.fishwatch.gov/seafood_profiles/species/cod/species_pages/atlantic_cod.htm
A point Stewart Brand does not make, but one I do, is that we are creating more species today than ever before because we are moving them around and allowing unimaginable cross-breeding, and we are also creating commercial species from wild animals.
Look at the number of non-native species in the U.S. from the Gemsbok to the Starling, from Russian boar to Asiatic deer. from red fox to dandelions and tumble weed. Each one of these species is now isolated from its former brethren, and will likely evolve in a different manner.
Then, we have animals like chickens, ducks, geese, horses, sheep, goats, and cows. We are making new varations every day and many of them are so divergent from their root stock that, if released into the wild (as some have been), we would consider them a different species. They are certainly as different from each other as a Barred Owl and a Spotted Owl!
If we lose a small, rare, endemic species of island finch, do we know it is even gone? And yet we mourn this loss even as we fully discount the creation of a two hundred kinds of chickens and 100 kinds of pigeons.
We mourn the loss of the Carolina Parakeet and the Passenger Pigeon, but if you look in any bird book, you will find that we have more types of wild parrots and parakeets in the U.S. now than at any time in history, and more kinds of pigeons too.
Again, I agree things are not as grim as some people would portray them, but they're not that great, either. You mention American megafauna. Sure, whitetail and mule deer are doing fine, but they're the exception, not the rule. There used to be 30 million bison, but today there are only 500,000. Thankfully, that is up from 100 in 1885, mostly due to bison ranching for meat, but it's still only 1/60th of what there used to be. As for elk, they used to be all over the Great Plains, also in their millions, before getting killed off and pushed back to marginal habitat. It's great that they're being reintroduced, but they are still nowhere near as abundant as they used to be. Ditto for pronghorn. And ditto for carnivorans like wolves, brown bears, and cougars. It's really sad.
Yes, reintroductions are great, but it's better not to lose animals in the first place. One reason is genetic diversity. Wildlife sometimes face exactly the same problem as purebred dogs: inbreeding depression. The best way to prevent this is to keep their numbers high, so you don't have to flirt with disaster when you try to build their numbers back up.
As for birds, the loss of the Carolina parakeet and the passenger pigeon are travesties. Steward Brand's group, the Long Now, hope to be able to clone them and bring them back (as other groups hope to do with the woolly mammoth and the thylacine). That would be great if it ever becomes reality, but right now it's science fiction. As with most things, an ounce of prevention is worth a pound of cure. So, with wildlife, the best thing to do is to conserve it so it doesn't have to be restored.
Extinction is a very different issue than disappearing baselines. Important to differentiate.
Baselines move up and down all the time, a point missed by environmentalists who worship stasis.
Ultimately, the question gets down to human population numbers. I am a radical in this arena, but if you are serious about population you have to take the first step which is surgical sterilization and children. I did that. As I said, I am a radical conservationist. But I am also a realist and not a worshipper of stasis. Mother Nature always bats last.
More here >> http://terriermandotcom.blogspot.com/2009/07/population-growth-and-limits-of.html?m=1
Yes, we mustn't worship stasis, as you say, that's very true. Nature is wondrous, but it ebbs and flows, and lifeforms and ecosystems change over time. You can't expect everything to stay the same forever. Having said that, some states of nature are better than others, and a prairie teeming with life is better than a feedlot filled with one type of livestock and its concentrated, polluting waste. Africa has its Serengeti, but American environmentalists have been calling for a Great Plains national park ever since George Catlin's day in the 19th Century. So yes, there is cause for optimism, but there is also cause for concern.
And yes, limiting the human population is extremely important. Genesis may tell people to "be fruitful and multiply," but that was written some 5,000 years ago when the infant mortality rate was around 30%, and the world population was around 5 million. In this day and age, having more than 0, 1, or 2 children is ecologically irresponsible. Whether it's humans or any other animal, too much of a good thing is a bad thing, and overpopulation leads to resource abuse and environmental decline. Of course, I am opposed to mandatory population control policies, and favor education instead. Moreover, wise management of natural resources is just as important as bringing down numbers, at any population size.
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