Wednesday, May 28, 2008

They were here, once.......

by Olivia Judson
Opinion: New York Times
Releasing a Carrier Pigeon (extinct)
(photo from SR News archive)

May 27, 2008, 11:00 pm
Musings Inspired By a Quagga

The Harpy eagle, Panama’s national bird, is an endangered species due mainly to poaching and to the destruction of the rain forests in Central and South America where it inhabits. (Credit: Elmer Martinez/Agence France-Presse — Getty Images)
The hall is hushed, like a church. No one else is here. The only sound is the clicking of the heels of my shoes. I walk up and down, looking at the animals. They make no noise, for they are dead.
Many of them are also gone. Like the quagga, a kind of zebra from southern Africa, which was hunted to extinction in the 19th century. It stares at me from behind glass. I stare back. It has a zebra’s face and neck, but lacks stripes on its torso, which is a dusky gray. Zookeepers said that the quagga was more docile than other zebras; but even in zoos there are none today.
A few glass cases later, I come to the O’ahu O’o’, a small, pretty bird from the forests of the Hawaiian island of O’ahu. A living specimen has not been seen since 1837. I pause to wonder about its mating display. Further on, there’s the desert bandicoot, a tiny creature with huge ears and kangaroo feet that had vanished from Australia by 1907. And now I’m gazing at the dark flying fox, a fruit bat from the Indian Ocean islands of Mauritius and Réunion. In the 1730s it was so abundant it was considered for commercial exploitation (the making of oil); by 1880 it had gone.
Here, at the natural history museum in Paris, in the hall of the endangered and the recently extinct, the vanishing and the vanished, it’s poignant to see these creatures. To put a few faces to the names, to visit a handful of representatives from the dreary and numbing statistics of forests felled and oceans over-fished.
Extinction is so much a part of today’s cultural background — this species endangered, that habitat lost, save the whale, save the rhino, save the rainforest — that it’s strange to think that as little as 200 years ago, most people didn’t think extinction was possible. The very idea was an affront to the Creator: it suggested imperfection and incompleteness in the original design of the world. So even once it became accepted that fossils had been formed from living beings — which itself took some time — most people supposed that the corresponding organisms were still alive, somewhere, awaiting discovery.
But in the last years of the 18th century and the first decade of the 19th, the great French anatomist Georges Cuvier made a study of the fossil bones of enormous animals — giant ground sloths, and extinct elephants like mammoths and mastodons. Some of the giant ground sloths reached 6 meters (almost 20 feet) long. The bones and teeth of mammoths and mastodons showed that they were clearly distinct from living elephants.
Cuvier argued that such creatures could not correspond to anything currently alive: if animals that big were still blundering around, they’d be known about. It was only then, in the years after he presented and published his work, that the reality of extinction in the history of life became recognized and accepted.
Two hundred years later, we are, perhaps, causing a series of extinctions on a scale that hasn’t been seen since an asteroid smashed into the planet 65 million years ago, and caused the extinction of the dinosaurs.
Well, so what if we are? From the Earth’s point of view, it doesn’t matter. Just as the emergence of new species is part of evolution, so is extinction. Most of the species that have ever lived are now extinct. Indeed, most species don’t last more than 10 million years or so anyway. The planet has already seen five mass extinctions — episodes of extinction where the rate of species vanishing is much, much higher than usual. During a typical mass extinction, more than 65 percent of species may disappear. The one that polished off the dinosaurs was by no means the most spectacular: 251 million years ago, at the end of the Permian period, 90 percent of species — including saber-toothed reptiles — were wiped out. (The causes are not completely clear, though the initial trigger may have been a series of gigantic volcanic eruptions. Nor do we understand why certain species survive a mass extinction, and others don’t.)
Moreover, each mass extinction has been followed by a pulse of fresh evolutionary change: large numbers of new forms appear. The reason is that before the mass extinction, most niches are occupied — a situation that typically prevents radical changes. Afterwards, many niches are empty and available for re-occupation — which promotes rapid change. (This is why new islands and lakes are always sites of rapid evolution and invention: the few animals and plants that arrive rapidly evolve to fill the various empty niches. Think of the Hawaiian islands, the Galapagos, New Zealand or Madagascar, each of which has — or had, until we got there — a variety of unique animals and plants.)
Taking the long view, then, the extinctions we are causing may open the way to a burst of evolutionary invention, the creation of new forms even more remarkable than those around today.
Only trouble is, we probably won’t be around to see it: after the dinosaurs vanished, it took 10 million years for diversity to recover. Ten million years! For us, that might as well be eternity. After the Permian extinction, the recovery took 100 million years. Eternity times ten.
And in the short-term, we may be in for a rough ride. How rough is a matter of angry debate. Some are blasé. Others forecast a catastrophe, arguing that extinctions will begin to accelerate, like an avalanche, and that the planet will soon become uninhabitable for us and our entourage.
Certainly, we’re having an impact. For example, fishing in the northwestern Atlantic has caused population collapses in several species of great sharks — including bull sharks, blacktips, dusky sharks, hammerheads. Since 1972, scalloped hammerhead shark populations off the coast of North Carolina have fallen by 98 percent; dusky sharks, bull sharks and smooth hammerhead populations have fallen by 99 percent. By comparison, blacktips are doing well: their population fell by only 93 percent.
The population crashes have had a big knock-on effect. The vanished sharks fed on skates and rays, which have seen their populations grow by a factor of ten. Cownose rays now number 40 million, up from 4 million in 1972. These animals feed on scallops and clams; the increase in their numbers recently caused the collapse of North Carolina’s bay scallop fishery. And this isn’t even a problem we can blame on climate change.
But to me, whether we need to save other species to save ourselves is not really the point. Each time a species vanishes, the planet becomes a poorer place. It doesn’t matter if we’ve never seen them, if they go extinct without our ever knowing they were here. To live is to participate in the carnival of nature, and the carnival is diminished by the losses.
For there is so much to marvel at. Like the spraying characid — a fish that lays its eggs out of water, jumping to stick them onto leaves that hang down over streams. (The male keeps the eggs wet by splashing them with his tail several times a day.) Or the just-discovered mimic octopus, which can assume the shape, colors and undulating swimming motions of a flat fish like a flounder. When it does so, the octopus even bugs its eyes out, so they look like flounders’ eyes.
Or what about the predatory fungi in the soil, which catch tiny worms by means of nooses and sticky webs. (When you get caught by a web of fungus, there is no spider. The web itself digests you.) Or, Philodendron solimoesense, a tropical plant that actively heats its flowers at night, keeping them several degrees Celsius warmer than the surrounding air. It does this to encourage scarab beetles — which serve as pollinators — to stay a while. Safe inside the warm flower, the beetles engage in riotous living: feeding and having sex during the night, and resting during the day. Or the Darwin frog: the male guards the tadpoles by keeping them in his throat. Or, or, or.
I wander over to look at a big bird with a fierce beak and a magnificent crest of white feathers. The harpy eagle, says the sign. Endangered.
What a shame.
La salle des espèces menacées, espèces disparues is upstairs at the Grande Galerie de l’Évolution at the Muséum National d’Histoire Naturelle in the Jardin des Plantes in Paris. For zookeepers on quaggas, see Nowak, R. M. 1999. “Walker’s Mammals of the World.” Johns Hopkins University Press. Volume two, page 1024. For commercial exploitation of the flying fox, see the IUCN redlist.
For a history of views on extinction, and Cuvier’s role in establishing it once and for all, see Rudwick, M. J. S. 1972. “The Meaning of Fossils: Episodes in the History of Palaeontology.” Macdonald and Co.
Mass extinctions of the past can be read about in any textbook on evolution, but for detailed discussions of the end-Permian extinction, the longevity of species on the planet, the recovery times after mass extinctions and references for further reading, see Erwin, D. H. 1993. “The Great Paleozoic Crisis: Life and Death in the Permian.” Columbia University Press, especially pages 261-264. See also Benton, M. J. 2003. “When Life Nearly Died: The Greatest Mass Extinction of All Time.” Thames and Hudson. For ways that high biodiversity can inhibit evolution, see de Mazancourt, C., Johnson, E. and Barraclough, T. G. 2008. “Biodiversity inhibits species’ evolutionary responses to changing environments.” Ecology Letters 11: 380-388.
There are any number of gloomy pronouncements about the impact of human activity; see, for example, Balmford, A. and Bond, W. 2005. “Trends in the state of nature and their implications for human well-being.” Ecology Letters 8: 1218-1234. For vanished sharks and the collapse of the bay scallop fishery, see Myers, R. A., Baum, J. K., Shepherd, T. D., Powers, S. P. and Peterson, C. H. 2007. “Cascading effects of the loss of apex predatory sharks from a coastal ocean.” 315: 1846-1850.
For the egg-laying behavior of the spraying characid, see Krekorian, C. 1976. “Field observations in Guyana on the reproductive biology of the spraying characid, Copeina arnoldi Regan.” American Midland Naturalist 96: 88-97. For the mimic octopus, see Hanlon, R. T., Conroy, L.-A. and Forsythe, J. W. 2008. “Mimicry and foraging behaviour of two tropical sand-flat octopus species off North Sulawesi, Indonesia.” Biological Journal of the Linnean Society 93: 23-38. For predatory fungi, see Kano, S., Aimi, T., Masumoto, S., Kitamoto, Y. and Morinaga, T. 2004. “Physiology and molecular characteristics of a pine wilt nematode-trapping fungus, Monacrosporium megalosporum.” Current Microbiology 49: 158-164. For heated flowers in Philodendron, see Seymour, R. S., White, C. R. and Gibernau, M. 2003. “Heat reward for insect pollinators.” Nature 426: 243-244. For the Darwin frog and his tadpoles, see Goicoechea, O., Garrido, O. and Jorquera, B. 1986. “Evidence for a trophic paternal-larval relationship in the frog Rhinoderma darwinii.” Journal of Herpetology 20: 168-178.
Many thanks to Dan Haydon, Gideon Lichfield and Elizabeth Pisani for insights, comments and suggestions.

1 comment:

PBurns said...

A couple of points about Olivia Judson's piece:

1. The quagga is not a species, but a subspecies.

2. It is not extinct.

3. The Harpy Eagle, named as endangered, is not endangered.

4. The story on extinction is not quite as grim as some would make it out to be.

For more, see >>