Clothesline in Winter

Clothesline in Winter

Wednesday, November 7, 2012

Mass Extinction #2: How Serious Is It?

A couple of weeks ago, we dipped our toe into the waters of species extinction. We were alarmed to find serious research indicating that the earth has likely entered a new mass extinction event, the sixth such event known to science. The most recent of these occurred some 65 million years ago, when the dinosaurs disappeared from earth.

Of course, we could not escape the nervy implication that our mass extinction could logically be called – perhaps by some researchers in the distant future – the event that ended the Age of Humanity. Or if that’s constitutionally or theologically beyond what we’re willing to consider, we still grapple with the possibility that it could signal the end for billions of our fellow humans. And by definition, it is the end of countless species of enormous value to their Creator.

So if it’s so, or even remotely possible, it’s certainly worth looking into. In this post, we take a closer look at some of the findings of the International Union for Conservation of Nature (IUCN). Specifically, we will address the following questions:

  • How many species are threatened with extinction?
  • What direction is the extinction threat trending?
  • What does it mean to be “threatened?”
  • How complete is our knowledge at present?
  • Why does it matter to humans?

How many species are threatened?

The IUCN maintains the “Red List of Threatened Species.” The Red List gives us two potentially different answers to the question: (1) Without a doubt, lots of species are likely to go extinct; but (2) We don’t know enough yet to confidently predict just how many. First, we’ll consider the “lots” response. Later on, we’ll take a look at the limitations on our current knowledge.

Roughly one in five vertebrates – mammals, birds, fishes and the like – are "threatened," according to the Red List. In fact, of the 64,283 known species of vertebrates, more than 56% have been assessed by the IUCN. Exactly 20% of these are threatened with extinction. That’s 7,250 species of animals in danger of disappearing forever. And that’s before any effects of climate change and ocean acidification in coming decades.

Here’s the summary data. I think you’ll agree it’s alarming:

If you look beyond the vertebrates, there are another 1.7 million known (or “described”) species – invertebrates, plants and the like. The picture here looks arguably even more alarming. Consider plants, for instance: almost 60% of the more than 15,000 assessed species are threatened with extinction. That’s more than all the vertebrates combined.

For invertebrates – insects, shellfish, corals, etc. – we see much more of the same. More than 13,000 invertebrate species have been assessed. And more than one in four of them are threatened with extinction.

Overall, the Red List has assessed 65,518 species, and 30.9% of them – almost one in three – are listed as threatened with extinction. If the data is at all credible, this should be setting off alarms in every corner.

What are the trends?

Since the year 1500, 869 species are known to have become extinct. In a world where we casually speak of millions and billions, perhaps we might take comfort that 869 doesn’t sound so bad.  But even if this were so, the trends are not favorable at all: The pace of extinction is picking up, and most have occurred very recently; extinctions are under-reported due to the difficulty of final confirmation; and species whose threat status is deteriorating far outnumber those that are recovering.

Leatherback turtles: Ancient species critically endangered
The plight of amphibians sheds some light on these findings. 38 species of frogs, salamanders and the like have gone extinct in the last 500 years. But 11 of these 38 extinctions have occurred in the last three decades. And while that sounds alarming, it doesn’t come close to telling the whole story. That’s because another 120 amphibian species have disappeared since 1980, and can no longer be found. Researchers are understandably cautious about declaring them extinct, but they’re missing. If they should indeed be extinct, then the pace of dying begins to look like a runaway train, with 27 species dying out over about five centuries, and about five times that number vanishing in the last thirty years.

If we look at surviving – but threatened – species of all kinds, we see a similar story. Between 2004 and 2008, 32 threatened species of mammals actually became less threatened – success stories for conservation advocates. But for every success, there were more than four failures: the threat status of 143 mammal species deteriorated during the same period.  For birds and amphibians, similar trends prevailed: 2 species of birds improved, while 30 deteriorated; only one amphibian species improved, while seven slipped closer to extinction.

What does it mean to be “threatened?”

The Red List contains three categories for species that are aggregated as Threatened: Critically Endangered; Endangered, and Vulnerable.  In assigning species to any of these three categories, researchers consider the following:

  • How much has the population declined?
  • Are the causes of decline reversible, ongoing or ceased?
  • What’s the absolute size of remaining population?
  • How rapidly is the species’ habitat being destroyed or altered?

To get a sense of how serious it is to be “Threatened,” let’s consider what it would take for humankind to make it onto the list. To begin with, the global human population would have to decline in amount as though everyone in the United States, China and the European Union instantly perished, assuming that the cause of our deaths had not been remediated. If whatever was killing us had been solved, then humanity couldn’t make it onto the list unless that death toll was increased to add India’s 1.3 billion plus all of South America, plus Indonesia.  And that only would get us into the least-threatened category – “Vulnerable."

If we were hoping that these categories were an exercise in alarmism, we are going to be disappointed.

What don’t we know?

Optimists and pessimists can both run a long way with the answer to this question. There is a lot that we don’t yet know.  In the last four years, the IUCN has added almost 21,000 new species to the Red List, an amazing feat in such a short time. While more than half of all known vertebrates have been assessed, the information is much spottier when we consider all living things: less than 4% of all known species have been evaluated. Invertebrates – particularly insects – figure prominently in this: Of the roughly one million known insect species, only 0.4% have been assessed. For spiders (arachnids), it’s even worse, with only 0.03% having been assessed.

Given the extensive work that's already been done on vertebrates, we can extrapolate current knowledge to the entire set with some confidence. About one in five species is seriously threatened. But when we add the vast masses of plants and invertebrates, extrapolation gets more dicey. About 31% of all assessed living species are threatened. But what about the remaining 96% that haven’t yet been assessed? Until researchers whittle that figure down, none will confidently make projections for the entire range of living things. But this much we do know: The familiar animals we know – excluding creatures like insects, spiders, corals, anemones and mollusks – are in serious decline under our stewardship.

Why should we care?

The IUCN goes on at some length about the numbers of threatened species which are used by people for food and medicine. Surprisingly, we learn that humans use almost 300 species of amphibians for these purposes, plus 22% of all mammals, and 14% of all birds. They tell us that a much greater proportion of human-used species are threatened than other species.

Golden toad: 1st climate change extinction?
I – for one – am left wondering if this approach does much to answer the question.  The utility of species can hardly be considered in isolation, as though some contribute to human interests and some don’t.  Rather, species are always part of ecosystems, complex symbiotic webs which we upset at our peril. As an example, 39% of the world’s hundreds of coral species are threatened. If they become extinct, we may perhaps regret the disappearance of beautiful coral reefs; we may tally the loss of tourism income at tropical resorts; and in the longer term, we may fret about the exposure of coasts no longer protected by barrier reefs. But surely, this approach fails to capture the vital role corals play in maintaining ecosystems teeming with plants, shellfish, anemones, plankton, herbivores and predatory fishes – often called the nurseries of the oceans. If corals die, as seems increasingly likely, I doubt any of us can confidently measure the consequences for the world’s oceans, and for humanity.

Perhaps Holy Scripture gives us a clearer way of thinking.  Genesis tells us that God created “every living and moving thing with which the water teems, according to their kinds, and every winged bird according to its kind. And God saw that it was good. God blessed them and said, ‘Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth.’”

We see in this account the pleasure God finds in each of his creatures, the sense that they are good, and that they should fill the seas, the land and the air. It’s unlikely that the ancient Hebrew writers fully understood the complexities of natural ecosystems. But they knew that God intended for his creatures to flourish. And they would recognize today's threatened state of many of his species as fundamentally out of synch with God’s creative purposes. 

Yes, living species provide us with food, medicine, and countless other benefits. But they also play unseen roles in balancing ecosystems upon which we rely. And in the final analysis, their Creator – and ours – demands that we commit ourselves to the kind of world in which they can flourish for his pleasure.

Thanks for reading, and may God bless you.

J. Elwood


  1. Great, but worrisome article. Thanks for writing and I look forward to the next extinction post.

    p.s. love the pictures.