I recently read The Future of Life by respected biologist, environmentalist, and Pulitzer prize-winning author Edward O. Wilson, who is not only the world’s foremost expert in myrmecology (study of ants) but also one of the most vocal crusaders for biodiversity.  And he’s not just a scientist, he’s a great lover of nature.  Early in the book he recounts one of the “most memorable events” of his life, when in 1994, in a back room of the Cincinnati Zoo, he encountered a four-year-old Sumatran rhinoceros named Emi.  He gazed into her “lugubrious face,” placed a hand on her flank, and communed with the solitary animal, as he pondered the critically endangered status of her species.

His love for nature leads Wilson to issue a harsh indictment:  “Humanity has so far played the role of planetary killer, concerned only with its own short-term survival,” he warns.  “We have cut much of the heart out of biodiversity.”  By this he means, we are responsible for a rise in the rate of extinctions and a decline in the remaining number of species.  The causes are well known:  hunting and poaching, loss of habitat, spread of invasive species, and now global warming.  Wilson states that by 2030, the species count for plants and animals could be down by 20%, and if we freeze conservation efforts at current levels, he claims that 1/2 of plant and animal species could be gone by 2100.

An Armageddon is approaching at the beginning of the third millennium. But it is not the cosmic war and fiery collapse of mankind foretold in sacred scripture. It is the wreckage of the planet by an exuberantly plentiful and ingenious humanity.

— Edward O. Wilson, The Future of Life

After finishing the book, I reflected on this warning.  I’m in favor of preserving wilderness, and I too would like to see the Sumatran rhinoceros flourishing again in the jungles of southeast Asia.  But for Wilson, biodiversity means more than protecting Emi, it means maximizing the total worldwide species count.  And here, his logic left me unpersuaded.  There are better metrics for measuring biodiversity, it seems to me, and stronger arguments for conservation.

What I most appreciated about the book was Wilson’s emotional connection with nature, and on the very last page, I thought his comments were spot on….

Biodiversity is commonly defined as “the variety and variability of life on Earth.”  For Wilson, one of the principal arguments for biodiversity is “insurance”:

Ecosystems are kept stable in part by the insurance principle of biodiversity. If a species disappears from a community, its niche will be more quickly and effectively filled by another species if there are many candidates for the role instead of few.

— Edward O. Wilson, The Future of Life

Arguments about the insurance benefits of diversification bring to mind the concept of modern portfolio theory, as developed by Nobel Prize-winning economist Harry Markowitz.  According to this theory, investment managers diversify their bets across a number of securities in order to minimize risk.

But minimizing risk is only half the story, for portfolio managers must also deliver returns.  That’s why they make bigger bets on securities that offer extra upside.  You can’t optimize performance through diversification alone, you need to balance risk with return.

Would Nature agree with Wilson that we need to sustain the maximum number of species?  Or would Nature follow Markowitz’ theory and place bigger bets on those species with the most growth potential?  I’d argue for the latter.  And in fact, Wilson presents an example of Nature backing away from the insurance principle, when he observes that human women opt for “a smaller number of quality children, when they can be raised with better health and education, over a larger family.”  He offers this observation in the hope that population growth will eventually slow, but it supports the point that quantity doesn’t always trump quality.

The rise of humanity has had a similar effect:  rapid growth in a small number of species, including ourselves, our domestic animals, and various invasive species that have ridden our coattails into new geographies, at the expense of a rising extinction rate among many other species.  The extinctions aren’t good, but at least they’re following on the heels of record levels of biodiversity.  According to the chart below, the marine fossil record implies there are today in excess of 5 million species, which is a tenfold increase over the last five hundred million years.  If the total count dips somewhat due to human activity, at least Nature should still enjoy significant diversification relative to past periods.

The chart also shows that the species count hasn’t risen smoothly.  Over the last five hundred million years, there have been five major extinction episodes, in which 60% or more of species died off.  For example, 250 million years ago, during the Permian-Triassic extinction event, also known as the “Great Dying,” 90-96% of all species went extinct, following extreme climate change that may have resulted from meteor impacts or volcanic activity.  Diversification doesn’t protect from correlated risks: for investors, a financial crash impacts all stocks, and for Nature, the insurance benefit withers in the face of global ecological change.

There are other problems with a focus on species count as the measure for biodiversity.  The chart above refers to 5 million species, whereas Wilson uses a figure of 10 million, but that’s just the median of scientists’ estimates, which range from 3.6 million all the way to 100 million.  Wilson acknowledges that “few experts would risk their reputations by insisting on this figure or any other, even to the nearest million.”  In other words, they don’t know.  Further, even for those species that have been identified, “fewer than 1 percent have been studied beyond the sketchy anatomical descriptions used to diagnose them.”  Specialists are overwhelmed by the flow of new species discovered every day.

While it’s relatively straightforward to count large species like rhinoceroses, it gets much harder for birds, plants, fungus, insects, nematode worms, and single-celled organisms.  In fact, for bacteria alone, some have speculated there might be as many as 10 quintillion species, outnumbering Wilson’s species count estimate by a billion-fold, while others say it’s impossible to know.  In which case, the species count is not a workable measure of the true biodiversity of life.

Yet Wilson is a big believer in species:

Each species—American eagle, Sumatran rhinoceros, flat-spined three-toothed land snail, furbish lousewort, and on down the roster of ten million or more still with us—is a masterpiece. The craftsman who assembled them was natural selection, acting upon mutations and recombinations of genes, through vast numbers of steps over long periods of time. Each species, when examined closely, offers an endless bounty of knowledge and aesthetic pleasure.

— Edward O. Wilson, The Future of Life

He bases this argument on the incredible amount of “pure information” contained in the genome of a single cell, which he reminds us contains as much information as “all editions of the Encyclopaedia Britannica published since its inception in 1768.”   Even a bug or a weed “is a creation in and of itself. It has a name, a million-year history, and a place in the world. Its genome adapts it to a special niche in an ecosystem.”

He’s making an important point about the value of information and the complexity of life, but species seems a rather limited measure for this concept.  The term is typically defined as a group of organisms in which two individuals are capable of reproducing fertile offspring.  But this definition doesn’t work across all forms of life.  Indeed, scientists have admitted they have a “species problem,” meaning disagreement on how precisely to define the term (there are apparently 26 different approaches).

To measure the value of information contained in the genome, we need to consider not only an organism’s reproductive classification, but also the complexity of its body, mind, and behaviors.  What Wilson has skipped over is the fact that humans are much more complex than other life forms, as evident in brains that contain 100 trillion neural connections, behaviors that are enormously diverse, and a collective social intelligence on a scale that is unprecedented for life on Earth.  With our minds amplified by computer technology and linked together in networks, we will soon usher in what some are calling the dawn of super-intelligence.

Wilson dismisses this vision as “technomania.”  It’s “a dangerous gamble, a single throw of the dice with the future of life on the table.”

But for better or worse, humanity is the new face of biodiversity.  Nature has made her bet.

Let’s conserve as much wilderness and protect as many species as we can, but let’s not justify these activities with unpersuasive arguments, because these won’t build the popular support necessary to get things done.  Instead, let’s be honest about the real reason for conservation:  many of us share a deeply-felt passion for nature.

When I got to the last paragraph of Wilson’s book, I thought he said this really well:

We need nature, and particularly its wilderness strongholds. It is the alien world that gave rise to our species, and the home to which we can safely return. It offers choices our spirit was designed to enjoy.

— Edward O. Wilson, The Future of Life