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Saving species, saving information

Recently it was revealed that since 1970, 60 per cent of all vertebrate animals on the planet have been wiped out.
opinion_ecologic1
People see evolutionarily isolated organisms such as the Platypus as both unique and "cool," which can be motivating to conservation efforts. shutterstock

Recently it was revealed that since 1970, 60 per cent of all vertebrate animals on the planet have been wiped out. Adding that to the fact that current whole-species extinction is running 1,000 to 10,000 times the background rate seen in the fossil record, the planetary biodiversity crisis seems only to be accelerating. Given that all life represents accumulated evolutionary information, the Earth is also facing an information crisis.

That disappointing revelation takes me back six years when scientists and philosophers gathered at Laurentian University in Sudbury, Ontario, to consider the meaning of what amounts to the sixth great extinction event in Earth's history. While uncomfortable applying medical metaphors like "triage" to endangered species conservation, its cost in time, energy and money saw most attendees at Thinking Extinction agree that some form of prioritization was necessary. At issue were the criteria and ethos for "valuing" species for conservation purposes.

To that end was a presentation by Dr. Arne Mooers, a biology professor at Simon Fraser University. His rhetorical title, "Are some species more equal than others?" was purposely Orwellian in presaging an argument that evolutionary isolation—as measured by "phylogenetic diversity"—might be a criterion for prioritizing conservation efforts.

To begin, Mooers noted this wasn't an entirely new idea. In 1982, celebrated biologist E.O. Wilson stated that conservation's ultimate aim should be to preserve all the information contained in the DNA of all currently living species. (Thus followed efforts like the Frozen Ark Project, launched in 1994 to freeze tissues, cells and DNA from all known endangered species; the more grandiose Earth BioGenome Project proposed in 2017 intends to sequence the DNA of all life on Earth). From this molecular milieu, Mooers plucked a notion both novel and practical—if choices had to be made around which species to conserve, maybe it made sense to choose those that carried the most information on evolutionary history in their DNA.

Biologists use diagrammatic trees to depict the evolution of species based on divergence from a common ancestor. Sometimes it's only the branching pattern that's of interest—who's related to whom. Increasingly, however, DNA sequence data is used to understand the timing and rate of divergence—in effect, the length of branches. In this view, if two species split from each other 20 million years ago, those two branches add up to 40 million years of independent evolution. By this measure, phylogenetic diversity is the total amount of independent evolution represented by adding branch lengths for a given set of species. For all 9,993 species of living birds, for example, Mooers calculated about 77 billion years' worth of evolutionary information; for the 575 of those species at risk of extinction, about 2.7 billion years.

Figuring out what that meant from a conservation standpoint suggested why biologists and philosophers could find common ground on the question of extinction: Can we identify species that we can't afford to lose because of the information they represent? Can we use evolutionary history as a guide? Can we make choosing which species to save less ad hoc—i.e., not because they're iconic or cute but because they're evolutionarily unique?

While evolution was important in and of itself, Mooers averred, he believed it could also be a proxy for other things. If, for instance, evolutionary history was used to prioritize saving species with few or no relatives—that is, the oldest, most isolated branches—this would, in effect, preserve maximum biodiversity because of the amount of unique information these represented. The argument was clear: use a family tree to find the lonely uncles and aunts, because if they go, all the information they carry on unique solutions for evolutionary problems goes with them.

By contrast, if a member of a more recent, more populous group disappeared, we might lose the organism, but not all of its information, because some of it was also carried by close relatives, and thus the biosphere had something to fall back on for potential replacement.

The proxy aspects weren't necessarily conservation criteria. For example, would prioritizing an isolated species deliver some other utility on the landscape in question? If, for instance, a broad array of organisms are saved by association, we could end up with things needed for a productive landscape, but also things we didn't know we needed.

Another interesting proxy was cultural. People see evolutionarily isolated organisms—aardvark, platypus, coelacanth, hoatzin—as both unique and "cool," which can be motivating to conservation efforts.

In the end, people understand "one-of-a-kind" because it makes animals and plants interesting and lovable, so they want to aid in saving them even if the real reason for doing so is the scientific argument that what it really conserves is information.

Leslie Anthony is a science/environment writer and author who holds a doctorate in connecting the dots.