Comic villains are always hatching nefarious schemes. These usually involve forcing a superhero to choose between saving an entire planet or the woman he loves. Why are ecologists finding themselves in the same position?

Today, real-life ecologists are being forced to decide which species to save when it's clear that not all are going to make it. Endangered species—and plans to save them—stir up passions. But some scientists are turning to a rather dispassionate solution for this issue: economics.

For example, breeds of cattle are going extinct quickly, and there's not enough money or interest to save all of them. So Australian researchers have turned to the theories of Harvard University's Martin Weitzman to try to figure out what species has the best chance, and would be the best investment of ecologists' time.

They determined that it makes more sense to save Ethiopian cattle over the similarly threatened Somalian and Kenyan breeds after factoring in not only that Ethiopian cows was the most endangered, but also that the herders would be the most willing to adapt and embrace conservation tactics to protect their breed. Voila!

Hopefully the Aussie researchers are correct and economics can be a tool to show the best ways of tinkering with ecosystems, because there are plenty of great examples where humanity's attempts to rectify its own negative effects on an ecosystem resulted in even further calamity.

Take the case of invasive species insanity on Macquarie Island near Antarctica: sailors in the 1800s accidentally introduce rats, then send in cats to kill the rats. They bring rabbits, too, so that shipwrecked sailors would have something to eat. Rabbits, as rabbits do, get out of hand, so scientists introduce a disease to kill them. This left the cats with less food, so they started eating the native species and wiping them out. So people had to kill all the cats. 

Macquarie is an extreme example of environmental manipulation gone wrong, but it's certainly not alone—remember the cane toads in Australia. With human activity and climate change threatening more and more species, sitting on our hands because we don't understand perfectly how our actions will affect the ecosystem isn't really a solution, either. 

Consider a kind of plan you're going to be hearing more and more about in the future—assisted colonization. Some animals—and plants, too—have already begun migrating to new areas as their habitats warm up and become less hospitable. But the pace at which animals adapt might not be able to keep up with accelerating global warming, if it comes to that. So said a paper in Science last summer, which suggested that manually moving some species to a more hospitable climate might be the only way to save them. These ambitious plans remain controversial among scientists, however, as evidenced by the response letters to that paper.

If economics can help tell us which cattle breed is the most salvageable, then perhaps it can also help to tell us whether assisted colonization really worthwhile. After all, it is a cost-benefit analysis: the benefit of trying to saving a species versus the costs, known and unknown, or the relative value of one species to its ecosystem over another. Given humanity's track record on this one, any help would be appreciated. These decisions aren't going away.