May 24, 2004

Disappearing Act

Filed under: Extinctions

The truth about species evolution and extinction is that humans are neither the question, nor the solution.

To what degree does human-influenced climate change impact species evolution and extinction? A great many government officials, scientists, and the media would have us believe that our role is significant. But climate change has been occurring naturally over eons, and species have emerged, evolved, and disappeared on their own since the dawn of time.

Is recent climate change outside the realm of natural fluctuation? And if so, is that “unnatural” change overstressing the planet’s ecosystems?

Recent Senate committee hearing suggests that it is. “Climate change is contributing to the changes in the migration and destruction of many species, causing the destruction of sensitive ecosystems such as coral reefs, despite our best management efforts,” Sen. John McCain told the Senate Committee on Commerce Science and Transportation’s Hearing on Climate Change Impacts and States’ Actions May 6. At least two witnesses at the hearing encouraged McCain’s view.

Harvard Medical School’s Paul Epstein, of the Center for Health and Global Environment, testified that “erratic weather is not good for our health and it certainly confuses the birds [while] plants are under attack from insects and fungi.” Yet that witness went on to undercut the logic of his assertion by explaining that “the battle between insects and plants began several hundred million years ago, when forests spread across the land. Trees fought back the leaf-eaters and bark-borers with chemicals, then garnered support from birds, spiders and ladybugs. Woodpeckers and nuthatches keep beetle numbers in check.”

In other words, species and ecosystem changes, including erratic weather, are part of dynamic nature.

But can’t species adapt to such changes by, for instance, relocating? Not according to expert witness William Fraser, president of the Polar Oceans Research Group. “Many wildlife species on the earth occupy habitats that are already compromised by human activities,” he testified. “Relocation in the face of climate change for these species is not an option, suggesting that extinctions will inevitably accelerate in the decades ahead.” Yet Fraser, too, undermined his opinion with this example: “Climate change in the western Antarctic Peninsula region is forcing a shift in the core ranges of wildlife populations, but suitable habitats available to absorb these changes remain. The findings presented in this testimony do not address the cause of climate change ….”

For our purposes here, we will ignore these witnesses’ imprecise notions such as “climate change,” “erratic weather,” and even the birds’ being confused by changing patterns of weather and climate in the face of evolution during several million years of continental drift, mountain-building, and extreme volcanism. We will simply agree with the expert witnesses that there is no evidence that the manmade greenhouse gases have ever been or will ever be the predominant or sole factor responsible for climate variability and “global warming.”

Undoubtedly, species evolution and extinction is a difficult and complex subject, and human influence on it still to some degree unproven, as a July 2003 article in Earth-Science Reviews makes clear. The title? “The Dubious Role of Man in a Questionable Mass Extinction.”

In no uncertain terms, author A.J. van Loon concludes that:

There are no convincing data either that the Stone Age societies (including people such as American Indians, Aboriginals, and Maoris in the past centuries) that possibly contributed to the disappearance of several large mammals did more harm to nature than other species did in the geological past. It seems therefore essential that insight into biodiversity and its fluctuations be deepened. [I]t must be admitted that activities in this framework get little attention thus far, most probably because the role of natural evolution is largely ignored—if recognized at all—by decision makers in the field of nature conservation.

In Earth’s history, the dominance of any species has been temporary. Van Loon points to the Mesozoic, from about 245 million to 65 million years ago, when reptiles dominated the ecosystem. Back then, the Sauria’s dominance forced “ever more other taxa to become extinct because the Sauria were able—roaming around in herds of giants—to chase the other taxa away from the areas with most food.” It may not be entirely clear why the reptiles (or even the bacteria) no longer dominate the earth. But man has apparently taken over that role of “chasing away animals from their natural habitats and destroying large ecosystems” today.

Beyond the “natural” (popularly defined as “without man”) background rate of species extinction, what is the “unnatural” extinction rate?

For man to be the major culprit to species extinction, van Loon “guesstimates” that the current rate of species extinction must be well over the naturally occurring rate of 20 to 100 species per year. But what has been observed today is not above that value.

The optimal way to estimate the “natural” extinction rate is by recognizing that some 50 billion species must have existed during the 3.5 billion years evolution of life on Earth, with only the last 2.5 billion years showing active appearance of new species and disappearance of old species. As a rough average, then, at least 20 species are being created and destroyed per year. Further refining that estimate by accounting for the rapid acceleration (more or less exponential) of evolution of life on Earth relevant to the present phase, van Loon suggests that “an estimate of about a hundred new appearances and equally many extinctions per year for our time might be a value in the correct order of magnitude” for the natural extinction and production rate.

Van Loon clarifies that “‘new’ species are being discovered and described in the scientific literature all the time, and they outnumber the species that we know to have become extinct recently. Scientifically speaking, the commonly assumed present-day mass extinction is therefore at least questionable.”

In any event, extinctions are difficult to prove, van Loon reminds us. The ancient fish species coelacanth (Latimeria), for example, dated as far back as 360 million years ago, until 1938 was believed to have become extinct 80 million years ago (http://www.austmus.gov.au/fishes/fishfacts/fish/coela.htm). But it was rediscovered after it had been thought extinct for a geologically long time. “Extinct” trees were found again in man-protected areas (as with Ginkgo biloba, preserved in the garden of the Chinese emperors) or even in the wilderness (the Wollemi pine [Wollemia nobilis] a dinosaur-era species, was found growing in Australia’s Wollemi Park in 1994). “Consequently,” writes van Loon, “it would be scientifically unjustified to blame man for all species that have disappeared (or that seem to have become extinct) in the past few thousand years.”

How about the popular ties made between species extinction and global warming or abrupt climate shocks as the ultimate destroyer of species and ecosystems? Van Loon identifies historical precedent for natural changes of similar—or even greater—magnitude, reminding us that humans are not the only cause of warming: “During a time interval of only 50 years (and probably much less) at the end of the Younger Dryas [about 11,400 years ago] the temperature rose some 6ºC, without noticeable influence by man.”

Indeed, van Loon explains, there are pertinent questions to ask when considering the effects of climate change on species extinction. For example, he writes:

Does the climate change that took place after the last ice age [about 20 thousand years ago] still have effect on biodiversity in the sense that some species are doomed to disappear locally because even the most resistant individuals will eventually not withstand the new conditions? And do species from other areas still infiltrate because the conditions are more favourable for them now (why did so many foxes adapt to life in cities such as London during the past decade)?

The natural consequence of species extinction and ecosystem destruction had been the arrival of increased biodiversity—humans included. Life is resilient. As van Loon explains, “mass extinction never posed a threat to life itself,” even during the Permian (about 290 million to 250 million years ago) and Triassic extinction episodes, in which 95% of marine life was killed and 70% of land families became extinct. In fact, he writes, that Permian-Triassic event “allowed not only sufficient individuals to survive, but also sufficient taxa to build complex new ecosystems in which numerous new species could develop to fill up the niches that had been created by the mass extinction.”

In other words, it is the natural reality of extinction events and species evolution that has led to the ultimate enrichment of ecosystems and biodiversity with niches and opportunities for new species.

“It is an interesting thought,” van Loon reflects soberly, “that modern man, Homo sapiens, would most probably not have developed if there had not been a mass extinction at the Cretaceous/Tertiary boundary that created apparently optimum conditions for the further evolution of mammals. This should make man much more humble than he is, and make him more reluctant than he is with respect to his present-day efforts to influence the evolutionary processes.”

In light of that perspective, is the notion of artificial “management efforts” for the preservation and maintenance of biodiversity, ecosystems, and species meaningful?

Here van Loon expresses his concern on two current major projects: namely, the Millennium Seed Bank in England and the Chinese Academy of Sciences Project for preservation of vascular plants “to safeguard the genetic variety of crops that might become extinct as a result of new diseases”:

It is to be expected that in the geological future new mass extinction will take place, not induced by man (or his successors!). It seems unlikely, however, that man will become extinct as a direct consequence. If he would nevertheless disappear from Earth, the present-day seed banks would have no function anymore. If man and some of the seed banks would survive, one might wonder whether the use of seed banks might be beneficial for the newly developing ecosystems; probably they would not. It thus seems unlikely that seed banks will contribute to new biodiversity after a mass extinction. It might even well be that the “old” species would prevent the explosive development of new species, which characterized the time immediately following previous mass extinctions. This would therefore represent a big influence of man on natural evolution and it is at least dubious whether such an interference would be beneficial for a natural restoration of balanced, interrelated ecosystems.

Ultimately, it ought not to be up to humans, who lack the incredible amount of knowledge to create a viable, balanced ecosystem, to arrogate the arrow of natural evolution and biodiversity by selecting specific ecosystems and species to be “preserved” for all time. Human efforts would be overwhelmed by nature’s infinitely greater competence. In the end, the notion of an absolute dominance of a species in deciding the outcome of species evolution and extinction at any given time on Earth is but an illusion.

Reference:

Van Loon, A.J., 2003. The dubious role of man in a questionable mass extinction. Earth Science Reviews, 62, 177-176.




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