Engineering Away Extinction, Ecological Functioning

Or might the threatened animal be just one of several subspecies that all perform approximately the same ecological function? In that case its extinction might be inconsequential. That was the reality when the Galapagos giant tortoise ‘Lonesome George’ died in June 2012 and was mourned worldwide. Dubbed ‘the rarest living creature’, he was (probably) the last of his subspecies. Ecologists shrugged. Taxonomists shrugged. There are 10 more subspecies of Galapagos tortoise. Their population has risen from about 3,000 in 1974 to more than 19,000 now, thanks to ridding their islands of all goats and most of the rats and protecting the tortoises from hunting. Pinta Island, where Lonesome George’s line evolved, is now occupied by other Galapagos tortoises that are doing fine, carrying on his old job of eating up the excess understory vegetation and helping restore the island to its former ecological health. (Tortoises are so good at that, it has become a standard practice. To help with ecosystem restoration, giant tortoises from the island of Aldabra, off the east coast of Africa, have been introduced to Madagascar, the Seychelles, Mauritius, Reunion, Rodrigues, and a park in Kauai.)

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An early success story stars a glorious tree – ‘the perfect tree’, according to its many fans in The American Chestnut Foundation. These trees once comprised one-fourth of the whole eastern deciduous forest before an invasive fungus from Asia killed billions of them and reduced the species to effective extinction early in the 20th century. William Powell and Charles Maynard at the State University of New York did an ingenious bit of genetic engineering to introduce a fungus-resistant gene from wheat, creating a blight-proof American chestnut that can begin to take up its former crucial role in the eastern forest, as soon as the US government okays it as a benign genetically modified organism.

How should we gauge the health of ecosystems? Biodiversity – the sheer number of species present – is one important measure, widely used. The return of American chestnuts will increase the biodiversity of the eastern forest by one species. But it will do much more. We might need to add another measure of ecosystem richness we could call ‘bioabundance’. Unlike oaks, which generate bitter-tasting acorns infrequently, chestnut trees rain down a deluge of sweet nuts every year, feeding no end of wild animals (and many a happy human). They make the forest more abundant.

The American Chestnut is an example of engineering life to thrive and refill its function in the ecosystem. Tortoises are other examples.