Extinction by unnatural selection

As Earth experiences the sixth mass extinction of life in its 4.6-billion-year history, evidence is mounting that one species is to blame: ours.

We have hunted to near or total obliteration many of the biggest, most charismatic animals, such as tigers and rhinos, as well as the once populous and mundane, from carrier pigeons to clams. Others are struggling in the face of our air, water and soil pollution, and our greenhouse gas emissions, which are changing the climate and acidifying the oceans. Changes in the land due to deforestation and the expansion of agriculture, the growth of infrastructure, the damming and diversion of rivers—all have taken their toll. We are transporting species around the planet, introducing predators and competition to endemic habitats, spreading pests and diseases, and shaking up trophic hierarchies. We have created genetically altered species, through breeding and other methods, to live in the places where their wild cousins once roamed.

In short, the brief time since humans evolved has been marked by the destruction and displacement of vast swaths of the natural world. In recent decades, our impact has increased to such an extent that humans now decide whether something lives or dies, goes extinct or proliferates. The current extinction rate is now as much as 1,000-times the natural one.

With this new power comes responsibility. We must make choices about what from the wild world we save, because it has become impossible to protect every species from untimely extinction. We can choose to save a portion of rainforest or a type of bee or shark. Or we can allow them to go extinct in favor of saving something else. How we make these decisions will set our relationship with the natural world for decades to come.

So what should win in the lottery of life: cute and cuddly; exotic and unusual; useful to humanity; useful to their ecosystem? People around the globe are grappling with the dilemma in different ways. The Edge of Existence program, for example, favors saving those that are evolutionarily one-of-a-kind species, whereas the general public prefers to save cute animals.

For many life forms, time is running out. We need, as a global community of humans, to make conscious decisions about what we want to save—and then set about doing it.

This column first appeared at The American Scholar.

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