According to David Quammen in his book, The Song of the Dodo, there are proportionately many more extinctions on islands than any other type of area. He writes, “Since the year 1600, according to [Jared] Diamond’s count, 171 species and subspecies of bird are known to have gone extinct. The earliest and most famous was the dodo. Of the total, 155 species and subspecies lived and died on islands. That’s more than ninety percent.” (1) That is, of 171 species and subspecies of birds that went extinct, 155 were from islands.
His book explains why this is so and (accessibly) explains the science behind island extinctions. One of the scientific theories that help explain this is the ETIB. ETIB is the thankfully shorter way of saying, the Equilibrium Theory of Island Biogeography. In the ETIB, the total number of species that live on an island is a cross between, 1) the total area of the land surface of the island, and, 2) how far away that island is from any other land mass. Apparently, islands do not have the highest species to area ratios, even though they may seem to be very rich ecosystems at first glance. Part of the problem is the difficulty species have of getting to the islands in the first place. An island that was formed by volcanic action, a true oceanic island, may not, for instance, have any frogs or toads on it. Certain species have great difficulty getting to an oceanic island. The other part of the equation is area. And this is key. To simplify, the more area an island has the more species it may be able to retain. And this has consequences far beyond islands.
Our parks and preserves are also like islands. Often in Illinois, for instance, a state park will be set in the middle of a sea of corn and soybean fields. The park or preserve is really acting the part of an island. On isolated islands like this, with all the pressures there are today on native species, from invasives to disease, etc., extinction from that preserve is just that much more easily accomplished. Of course, populations could be artificially brought from another preserve to help supply an ailing population; that’s one possibility. But this also shows us how in our parks and preserves we must be constantly at work to survey populations (for example, insect populations or plant populations) and to manage the site so as to watch out for waning populations. Protection and preservation are important, but they must be accompanied by effective management.
The Next Step
On islands, total area is small. Populations tend to be small and fragile. And something like this is also at work in freshwater habitats. Less than 1% of all the water on earth is freshwater. And this includes glacial ice like that on Greenland and other places. Proportionately, freshwater environments are smaller and more fragile than many others on continents. (There are also many stresses on freshwater environments which include – pollution, dams, invasives, boat and barge traffic, silt and runoff from farms and cities, and invasives discharged in the ballast water of ships, etc.) One would expect therefore that extinctions in freshwater environments would be increasing in recent history. In fact, among the 300 freshwater mussels of North America, the U.S. Fish and Wildlife Service estimates that 70% are either already extinct or in peril. (2) And according to the U.S. Fish and Wildlife Service again, 37% of freshwater fish in the U.S. are at risk of extinction, and 35% of amphibians that depend on aquatic or wetland habitats are rare or imperiled. (3)
So the next step is really extinctions on continents. One can expect more extinctions to occur in small or specialized habitats. The Kirtland’s warbler, which occupies rare jack pine forests in northern Michigan is an example of a species inhabiting a specialized habitat and on the brink of extinction. And even more “common” birds, as the Audobon Society recently reported, are in danger also. (4)
As I’ve said, we need to manage our natural areas, but we also need far ranging protections to protect the web of life, even on continents. The Endangered Species Act is a powerful tool that helps us to save species before they go extinct, but the real goal is healthy ecosystems (although that’s hard to define). There are things we can do to help get us closer to that goal. One current one is wetlands protection. The Clean Water Restoration Act of 2007 (H.R. 2421) will apparently protect our wetlands again, after the Supreme Court ruled a few years ago that, to be protected, wetlands had to be connected to a navigable waterway. We can protect wetlands with one fell swoop with this law, and that will help us protect natural areas and the web of life here in the U.S.
Net Primary Production
I’ve mentioned Net Primary Production before. Basically, it is the amount of energy plants and plankton create, making life on earth possible for every other living thing (whether plant-eating or animals eating animals that eat plants). I’ve read some of the literature online about net primary production and it seems to vary what percentage of net primary production it is estimated that humans use. A rough figure would be 10-30%. (6) Even so, this is a lot, I think, for one species to appropriate. The problem here is one of deep ecology, and it’s related to the land area problem as well. Less land area for wildlife means less wildlife no matter how you look at it. Less energy in the ecosystem for wildlife means the same thing – less wildlife. We are putting the natural world through a kind of funnel where not as many resources are available to it to continue and evolve.
And that’s what deep ecology is about. It’s the idea that we have to protect our natural world to the point where it can continue to grow and change over time, and that means the ability to continue evolving. It means healthy populations, ready, because of large healthy gene pools, to meet change and stress. (Global warming may teach us a few things about this, about how ready our natural populations are for the stress of changing temperatures.)
We have a long way to go. But we have made a good beginning with the laws and the advocacy groups that we have. On the other hand, if we’re waiting for aliens from other worlds to help us, then I think we’re going to be disappointed. If we are going to save this world at all, we’re the ones who are going to have to do it.
(1) Song of the Dodo: Island Biogeography in an Age of Extinctions, David Quammen. — NY: Simon and Schuster, c1996, p. 264.
(2) “Discover Freshwater Mussels: America’s Hidden Treasure,” U.S. Fish and Wildlife Service. www.fws.gov/news/mussels.html
(3) This is a strange document, but it has the information – from the U.S. Fish and Wildlife Service. www.fws.gov/endangered/recovery/39-56.pdf
(4) Audubon Society article – “Common Birds in Decline” –
(5) Two articles follow, rather difficult to read, but are worth the try –
This is the article that got the ball rolling on human appropriation of net primary production, (HANPP) –
The best general article I’ve seen on the mussels is this –
NOTE: (4/25/10) Here’s some evidence of the prediction that more species of freshwater habitats are likely to go extinct. http://www.biologicaldiversity.org/news/press_releases/2010/southeast_petition-04-20-2010.html