Last Chance to See – the Sixth Extinction?

Per the advice of my fiancé, I recently took the opportunity to read Douglas Adams’ and Mark Carwardine’s book Last Chance to See. I undertook the task a little reluctantly, not because of any particular lack of interest, but because my graduate research leaves me with very little time for recreation reading. This, of course, is my excuse whenever I’m disinclined to do anything. In this regard, it has been extremely useful, since it generally relieves me of the burden of the sort of careful introspection that might be involved in actually articulating and justifying my motives – whatever they may be.

So, after several months of careful procrastination, I finally cracked the cover. Until that time, I was only familiar with Douglas Adams by reputation. This is probably a boarder-line heretical confession for anyone even marginally interested in science fiction, humanism, conservation, science, and – as I came to discover – really good prose. I don’t think it’s an exaggeration to say that, in terms of sheer wit, Douglas Adams rivals Mark Twain. Of course, the stylistic merits of Last Chance to See are merely a footnote. The real force of the work comes from its content.

Last Chance to See is a globetrotting adventure, with Adams accompanying zoologist Mark Carwardine on a trek to locate and observe a few of the endangered species list’s more prominent members. The impetus for the large work was a 1985 aye-aye hunting trip to Madagascar. Adams and Carwardine were hunting the aye-aye for purely journalistic reasons: being critically endangered (according to contemporary knowledge) the actual slaying of an aye-aye would have been grossly unethical. In any event, the 1985 Madagascar trip laid the seed for the larger work of Last Chance to See, commissioned as a companion book to the 1989 BBC radio series of the same name.

 

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An aye-aye. Illustrated by Joseph Wolf. c. 1863

Over a roughly ten month period of time, Adams and Carwardine travelled around the world documenting threatened species. On the Indonesian island of Komodo they encountered the eponymous dragon – a species of massive monitor lizard endemic to that island (and the surrounding islands of Gili Motang, Gili Dasami, Rinca, and Flores) with a population thought to number somewhere in the thousands. The portrait Adams paints is dismal. Though the komodo dragon is relatively secure (relative to other threatened species) the animals Adams and Carwardine encounter have been reduced to a tourist attraction – a spectacle for migratory herds of Western geriatrics. As Adams notes for multiple species throughout the book, this is a matter of cold pragmatism – species that pay their way through the tourist trade are less likely to have their right to life usurped by other, more profitable interests. Listed as vulnerable according to the IUCN (International Union for the Conservation of Nature), komodo dragons presently benefit from residence within an Indonesian national park, designated since 1991 as a UNESCO world heritage site.

Following their trip to Indonesia, Carwardine and Adams head west to look for northern white rhinos and mountain gorillas in Zaire. This brings them face to face with the bureaucratic inefficiency and corruption so pervasive in many African nations – the callous legacy of European colonialism. Adams, Carwardine, and crew navigate a labyrinth of bribes and crumbling infrastructure in order to find a pair of species hovering on the brink of extinction. At the time of his writing, there were less than 300 mountain gorillas in the wild. The situation for the rhinos was much worse – only 22 were known to freely (more or less) roam the savannah. The gorilla population had already reached its nadir in the early 1980s, when a bit less than 260 were thought to remain. Since then, their numbers have steadily increased, though the species remains critically endangered according to IUCN listings. The northern white rhino, on the other hand, is in much worse shape. As of 2006 there were only 4 individuals known to exist in the wild. There have been no confirmed sightings since and it is quite possible that the northern white rhinoceros, as a truly wild animal, is extinct.

In New Zealand, the author’s search for kakapos, a species of flightless parrot that famously tried to mate with Mark Carwardine’s head while shooting the 2009 follow-up to the original BBC radio series/book. Considerable hassle leads them to a pre-dawn encounter with one of but a few remaining kakapos. In China, they look for Yangtze river dolphins (baiji) – and find none. On the island of Rodriguez in the archipelago nation of Mauritius they easily locate Rodriguez fruit bats (flying foxes) and suffer the consternation of conservationists who wonder why anyone would come to look for the bats when so many of the island’s inhabitants are much worse off.

Stephen Fry watches as a kakapo attempts to mate with Mark Carwardine’s head. 

As of this writing, the kakapo is a bit better off than it was in the late 1980s, but still in pretty bad shape. The IUCN lists it as critically endangered, with a total population of around 130. The last known baiji died in 2002, though a fisherman filmed something tentatively confirmed as a river dolphin in 2007. Even so, one individual – or even a handful – does not a species make. By all practical measures, the Yangtze river dolphin is now extinct. Despite successful captive breeding programs, Rodriguez flying foxes number only a few hundred in the wild. Their IUCN status is critically endangered.

Naturally, Last Chance to See‘s coverage of endangered species is not comprehensive. The species discussed are the more charismatic representatives of what many believe to be a larger crisis in biodiversity that might even merit classification as a mass extinction. If so, it would mark the sixth such mass extinction event in our planet’s 4.54 billion year history – referred to by some by the slightly less dramatic moniker, Holocene extinction.

As the name might indicate, the Holocene extinction has been occurring since the end of the Pleistocene and the onset of the modern period of geological history known as the Holocene (roughly 11,500 years ago). It was around this time that some the more well-known prehistoric mammalian mega-fauna – woolly mammoths, giant ground sloths, smilodons (saber-toothed cats) etc. – reached their historical nadir, which, as it happens, is zero. The exact causes of their misforutune are unclear, but a number of compelling, non-exclusive hypotheses have been forwarded including a global shift to a warmer climate regime, the spread of infectious disease via human vectors, and direct human overkill1. Each of these hypotheses has some empirical basis, though the disease hypothesis hasn’t fared quite as well as its peers. The most reasonable assessment is that the late Pleistocene/early Holocene mega-fauna extinctions were the product of synergistic effects produced by the interactions between climate change and human predation with disease potentially compounding the effects of the latter two pressures.

mammoth-hunt-Old-Vero-Man-site

Since then, extinction seems to have continued more or less apace before accelerating with the onset of the industrial revolution and the associated explosion in human population. But whether this qualifies as a mass extinction or not is not entirely clear. The evidence here is not unequivocal. According to  paleontologists, the threshold for mass extinction is a loss of 75% of species over a period of 2 million years or less2. The question we face is whether or not modern species loss match these criteria in terms of magnitude (total percent of species lost) and rate (the period of time over which loss occurs). Finding an answer is a thornier problem than one might expect.

Ecological pressures do not affect species uniformly – a stress that pushes one species to the brink of extinction might have little or no impact on another. Consequently, present extinction trends are not evenly distributed. Amphibians have been particularly hard hit by modern ecological stresses, such that approximately one third of the 6,300 known species of amphibians are threatened with extinction1. But they are not alone in their plight. Depending on bio-geographic region, North American mammals have experienced a drop in species diversity of between 15 and 42%3. The numbers vary, but the overall trend is the same for every type of organism, from plants to birds – numbers are waning and the trend seems to be accelerating.

The data on the rate and magnitude of modern extinction (defined as within the last 10-13,000 years) should be distressing to all but the most callous of observers. They are not, however, on par with what has been traditionally defined as a mass extinction event. That assessment should not alleviate our alarm at the continuing loss of biodiversity. Other indices indicate that the modern rate of extinction is, if not outright massive, certainly unusual.

Another way of looking at extinction rates is to examine how much they differ from a historic baseline that reflects the average rate of extinction over a long (several million year) stretch of geologic history. In one study2, researchers attempted to conservatively assess the severity of modern extinction by comparing the minimum modern E/MSY (extinctions per million species per year) with the maximum historical baseline E/MSY. The modern E/MSY was estimated to be between 24 and 693, depending on whether extinction is measured over a 1,000 year average or in single year bins. Compared to the historical baseline E/MSY of 1.8, it would seem modern extinction rates are well in excess of what would be expected under typical conditions. As mentioned, this is an extremely conservative estimate. Other researchers4 estimate modern extinction rates are between 100 and 1,000 times greater than pre-human averages.

This can be viewed as problematic for any number of reasons, foremost among them being the decreases in ecosystem stability associated with decreases in species diversity. Ecosystems are commonly depicted as webs of interactions that connect primary producers (plants) with top predators and everything in between via complex chains of interaction. As diversity decreases, the importance of individual interactions increases4,5. For example, imagine a hypothetical big cat that preys on a species of deer, a species of peccary, and species of large rodent. Now imagine that the species of deer is driven extinct. The cat now depends on fewer prey species in order to survive. This simultaneously constrains the size of the cat population while increasing the importance of the peccary and the rodent. If one of those now goes extinct, the cost to the overall ecosystem is greater than it would have been otherwise. Though grossly oversimplified, this example illustrates how decreases in biodiversity increase an ecosystem’s sensitivity to new stresses. The less diverse the ecosystem, the greater the probability of it experiencing a shock that will result in a cascade of cataclysmic changes, up to and including potential ecosystem collapse.

The extirpation and reintroduction of wolves in Central Idaho and the Greater Yellowstone ecosystem provides an informative natural experiment in this regard. In the late 19th and early 20th century, the gray wolf was viewed as a menace. By 1926, active hunting and the practice of lacing animal carcasses with strychnine had resulted in the eradication of wolves in the Western United States. Suddenly released from the pressures associated with an apex predator, elk populations increased substantially. Unmitigated by wolf predation, elk grazing decreased recruitment of tree species and damaged riparian ecosystems6,7 with negative consequences for beavers, moose, and other species that depend on riparian habitat to survive and thrive. The reintroduction of the wolf in 1995 resulted in what ecologists refer to as trophic cascade. Without the stress of constant grazing, riparian ecosystems have bounced back, rejuvenating beneficial habitat for a range of species. Scavengers from grizzly bears to ravens have also benefited from an increase in carrion associated with wolf predation8.

Long story short, the extirpation of the gray wolf was bad for the ecosystem. Relative to the ecology of the inter-mountain west, its reintroduction has been unambiguously good.

Unfortunately, there are many in this world who only measure the worth of a thing in dollars and cents. These are people who, as Oscar Wilde put it, “know the price of everything and the value of nothing.” That is explicitly why the survival of species like wolves, mountain gorillas, and komodo dragons is largely dependent on their adoption as commodities in the tourist trade. History has hitched the world’s metaphorical wagon to the yoke of capitalism. I certainly don’t want to go all commie here, but the fact of the matter is that the driving force of capitalism is short-sighted self-interest. The market has no foresight. It is the emergent product of individuals competing to maximize their short-term interests. Because of this, not only do many fail see the costs associated with decreased biodiversity, they fail to see a reason why they should do anything about it. The primary driver of social action – monetary interest – has no mechanism by which to respond to species loss.

As the Economist recently reported, the over-exploitation of the world’s maritime resources has placed important fisheries in a position where they stand on the brink of collapse. The world’s oceans remain largely unregulated in terms of economic exploitation, both real and potential. That means agents are free to pursue their short-term interests regardless of the long-term consequences. In general, that spells disaster for an absolutely critical ecosystem that should properly be viewed as a common inheritance – not only for future generations of humanity, but for all life in general.

The oceans exemplify the “tragedy of the commons”—the depletion of commonly held property by individual users, who harm their own long-term interests as a result. For decades scientists warned that the European Union’s fishing quotas were too high, and for decades fishing lobbyists persuaded politicians to ignore them. Now what everyone knew would happen has happened: three-quarters of the fish stocks in European waters are over-exploited and some are close to collapse.

The salient feature of such a tragedy is that the full cost of damaging the system is not borne by those doing the damage. This is most obvious in fishing, but goes further. Invasive species of many kinds are moved around the world by human activity—and do an estimated $100 billion of damage to oceans each year. Farmers dump excess fertiliser into rivers, which finds its way to the sea; there cyanobacteria (blue-green algae) feed on the nutrients, proliferate madly and reduce oxygen levels, asphyxiating all sea creatures. In 2008, there were over 400 “dead zones” in the oceans. Polluters pump out carbon dioxide, which dissolves in seawater, producing carbonic acid. That in turn has increased ocean acidity by over a quarter since the start of the Industrial Revolution. In 2012, scientists found pteropods (a kind of sea snail) in the Southern Ocean with partially dissolved shells.

A storm of economic costs is brewing on the horizon, but the market – composed of people who live in the present and will likely die before the full costs are realized – has very little incentive to react. The inertia of the system may very well carry us into disaster.

There are those that might cry foul at this point, noting that extinction is a natural process. The modern loss of diversity might not be caused by man*. After all, 99% of the roughly 4 billion species that have ever inhabited the earth are extinct. Extinction, it would seem, is the rule rather than the exception. There are at least two responses to that argument. First, available evidence indicates that humans are in fact responsible – either directly or indirectly –  for a considerable amount of the modern loss in biodiversity. Humans have transformed 40-50% of the earth’s ice-free land from forest, wetlands, and prairie into pastures for domesticated animals, fields for crops, and cities, resulting in considerable habit constriction and fragmentation5. A 30% increase in atmospheric carbon, linked with industrialization, has resulted in the most rapid rates of climate change in the last 18,000 years5. Pollution is directly implicated in the extinction of the Yangtze river dolphin. Direct exploitation – in the form of poaching – is behind the likely extinction of the northern white rhino and the critically endangered status of the mountain gorilla. Only 130 kakapos remain due in large part to the human introduction of invasive species like rats and feral cats to otherwise pristine island ecosystems – a similar fate probably befell the dodo of Mauritius. The giant moas of New Zealand were hunted to extinction following the arrival of the Maori.

 

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Human and domesticated animal biomass vs. wild mammal biomass. Via xkcd.

The second response is the one given by Douglas Adams in a short epilogue to Last Chance to See. It is the story of the Sibylline Books. According to myth, there was once a prosperous city, its inhabitants wealthy, living a lifestyle of lavish excess and extreme comfort – able to indulge their every hedonistic whim. One day an old woman showed up at the gates carrying a bag of books. There were twelve of them, which the woman claimed contained all the knowledge and wisdom in the world – everything anyone could ever want to know about anything. She offered to sell them to the city’s inhabitants for a single bag of gold. Wanting for nothing, the citizens scoffed at this and turned her away. In response, the old woman asked for a bundle of firewood. The citizens obliged and the old woman proceeded to burn half the books.

A year later, the woman returned. Again she offered to sell her books, now reduced by half. But now the price had doubled. The city and its inhabitants were still pretty well off and quite pleased with themselves, so they turned her down. The woman burned another half of the books.

Another year passed and the woman came yet again. She made her offer: three books – one quarter of all the knowledge and wisdom of the world – for four sacks of gold. Things were taking a bit of down turn in the city – people didn’t have the extra money to spend on books – so they sent her away again. They didn’t even have any surplus firewood to offer the woman to burn her books with. Being a resourceful old lady, she shredded two of the books and set them aflame.

When she returned the next year the city and its inhabitants were pretty bad off. Times were desperate. The old woman offered to sell them the final book, the final twelfth of all the knowledge and wisdom in the world, for sixteen sacks of gold. The citizens were naturally confused by the sudden inflation – hadn’t the books been doubling in price each year? The woman explained that times were tough and that was her final offer. The citizens gathered every last scrap of gold they could find.

It barely turned out to be enough.


 

When I ponder the staggering ecological costs humanity has inflicted on the earth – the wholesale slaughter or indirect eradication of huge quantities of nonhuman biomass – I can’t help but think of it as some kind of crime. Humanity has been engaged in the ruthless elimination of other organisms for millennia, sacrificing countless individuals on the competing altars of crude self-interest and abject ignorance. It is a pattern that has accelerated in concert with industrialization, globalization, and population growth. Like the genocides humans have carried out against their own kind, is a problem facilitated by an inability to see others, if not as the same as one’s self, as nonetheless intrinsically valuable.

This brings to mind a scene from one of the Pirates of the Caribbean movies. Following the first entry those films quickly descended into absolute rubbish, but there is moment from the third entry in the series that has always stuck out in my mind. Perhaps this is a silly example, but I think it makes salient some of my feelings concerning the damage we, as a species, have inflicted – and are continuing to inflict – on the natural world. Jack Sparrow and his perpetual rival/opportunistic ally Barbossa are standing on a beach, looking at the corpse of a giant kraken, probably the last of its kind.

Barbossa remarks: “The world used to be a bigger place.”

Sparrow responds: “The world’s still the same. There’s just less in it.”

Works Cited:

  1. Wake, David B. & Vance T. Vredenberg. 2008. Are we in the midst of the sixth mass extinction? A view from the world of amphibians. PNAS. 105(1)
  2. Barnosky, Anthony D. et al. 2011. Has earth’s sixth mass extinction already arrived? Nature. 471(7336):51-57
  3. Carrasco, Marc A., Anthony D. Barnosky, and Russell W. Graham. 2009. Quantifying the extent of North American mammal extinction relative to the pre-anthropogenic baseline. PLoS One. 4(12)
  4. Chapin, F. Stuart et al. 2000. Consequences of changing biodiversity. Nature. 405
  5. McCann, Kevin Shear. 2000. The diversity-stability debate. Nature. 405
  6. Beschta, R. L. 2003. Cottonwoods, Elk, and Wolves in the Lamar Valley of Yellowstone National Park. Ecological Applications 13:1295-1309
  7. Beschta, R. L. 2005. Reduced Cottonwood Recruitment Following Extirpation of Wolves in Yellowstone’s Northern Range.
  8. Wilmers, C. C., R. L. Crabtree, D. W. Smith, K. M. Murphy and W. M. Getz. 2003.Trophic Facilitation by Introduced Top Predators: Grey Wolf Subsidies to Scavengers in Yellowstone National Park. Journal of Animal Ecology 72:909-916

* I ignored two issues in my discussion of extinction as a natural event. First, there is the sad fact that many people believe the modern ecological crisis is the work of divinity. This is entirely ridiculous and not really worthy of consideration. And, as I’ve written elsewhere, the sort of people who believe that sort of thing are the most insular, tribal, and intransigent folk imaginable. No amount of rational argument or empirical evidence is going to change their mind. Second, it is a false dichotomy to speak of events caused by human action as somehow separate from nature. Humans are as natural as anything else that has ever existed. When discussing issues like climate change and biodiversity loss, the point of the distinction is to narrow the focus to single cause: Homo sapiens. This delineation is worthwhile because, insofar as the world is suffering as a result of our behavior, we have a responsibility to do something about it.

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