Steve Perlman doesn't let anything, even hundreds of feet of vertical cliff, get in the way of his efforts to find and save endangered plants in the wild.

If he encounters a steep drop while traipsing through the most rugged vegetation in Hawaii or on other Pacific islands, Mr. Perlman simply pulls out ropes and rappels down to where he wants to go. Once you're out there, he says casually, "you just want to keep going. You don't want to be stopped by a waterfall, you want to see what plants are on those steep cliffs." And at 69, he's still roping into uncharted territory looking for rare plants.

Perlman’s brand of extreme botany, as he calls it, is just one example of heroic conservation efforts going on around the globe. But not everyone agrees on the best way to save the vast amount of the natural world that is under threat. Some say conservationists should use some sort of triage system to prioritize which species or ecosystems get attention, while others suggest that every species is valuable and deserves conservation attention.

For Hugh Possingham, chief scientist of The Nature Conservancy, it’s a matter of saving as many species as possible, with limited resources.

“I suppose the question is not how far should we go to save a single plant species, it is what can we do with the resources we have,” says Dr. Possingham.

Acknowledging the limits on time and financial resources, Possingham has developed a formula for prioritizing conservation projects that also takes into consideration the number of species that could potentially benefit from each project and the probability of success.

“The system favors those species that are most in danger of extinction,” Possingham says, “but it is countered by the fact that sometimes those species that are most in danger of extinction are the ones that are harder to save, or more expensive to save.”

Perlman and Possingham bookend an ideological spectrum of views in the conservation world. Both are profoundly dedicated to preserving biodiversity but approach the problem from vastly different perspectives. Where Possingham finds clarity in careful cost-benefit analysis, Perlman functions in a perpetual race against time.

Divergent models of conservation

In Hawaii, where Perlman works as a statewide specialist for the University of Hawaii’s Plant Extinction Prevention Program (PEPP), there are 238 known plant species teetering on the brink of extinction, each with fewer than 50 individuals left in the wild. To Perlman and his colleagues at PEPP, each one of those species deserves saving. And he is willing to do whatever it takes to try to save them: fencing off plants to keep out goats, pigs, and other grazers; rappelling off cliffs to collect seeds and pollen; and even hand pollinating the last few individuals of a species.

Eva Botkin-Kowacki/The Christian Science Monitor Steve Perlman points to the Waimea Canyon on Kauai, where he has made numerous exploratory botany trips. The canyon was once dotted with the white of the flowers of the now-rare Hibiscus waimeae, which is only found on Kauai, he recalls.

But on a global scale, nurturing each individual species back to health is a more weighty proposition. One in five of the world's plant species is threatened with extinction, according to the annual State of the World's Plants report from Royal Botanic Gardens, Kew. That's a lot of plants that need tender love and care – and money – to keep them from going extinct.

That’s where Possingham’s formula comes in. In New Zealand, for instance, where nearly a third of the archipelago’s indigenous plants are threatened, Possingham’s calculated approach has enabled conservationists to make educated decisions about where to allocate funds. In some cases, his formula has helped Kiwis stretch conservation dollars to save more species.

On the other end of the ideological spectrum, however, conservationists like Stuart Pimm worry that the triage-based approach not only dooms species that potentially could have been saved, it also stymies innovation.

“As a scientist, I think triage is such a bad idea because it doesn't advance the field,” says Professor Pimm, a conservation ecologist at Duke University in Durham, N.C., whose research is behind the widely cited figure suggesting that species are going extinct as much as 1,000 times faster than the background rate of extinction.

When biologists are fighting to save the last few individuals of a species from extinction, they are driven to innovate, he says. And through this process, “We are getting very, very much better at saving species from the brink of extinction,” he says. “We have forced ourselves not to write species off.”

What’s at stake?

One risk of extinction is that when a species disappears, its absence could disrupt other parts of the ecosystem if, say, it was the primary food source for a particular animal. But even if other species can fill the newly extinct species' ecological niche, something specific will still be lost: its genetics.

“Every species that is lost, I think it's fair to say, is a treasure that is gone forever,” says Ruth Shaw, a professor of ecology, evolution, and behavior at the University of Minnesota. Each species is genetically unique, she says, and “the diversity that we have came about through just awe-inspiring expanses of time, and is not replaceable in any kind of a time frame that we can understand.”

Preserving one-of-a-kind genetics is one of the reasons that Perlman and other botanists around the world collect seeds and cuttings of rare plants that can be stored in seed banks, tissue preservation facilities, or at least grown in captivity.

Eva Botkin-Kowacki/The Christian Science Monitor Brighamia insignis once grew all over the cliffs of the Na Pali coast on the Hawaiian island of Kauai. But after two hurricanes slammed the island, just one plant is known to remain in the wild. But the plant, sometimes called vulcan palm or cabbage on a stick, lives on in homes across Europe as a houseplant, thanks to Steve Perlman's seed collection efforts. Some, like these pictured, grow in nurseries at the National Tropical Botanical Garden on the island of Kauai in Hawaii.

But the value of the genetics of the world's flora goes beyond simply being impressed by the feat of evolution that led up to today. Having a variety of plant genetics to draw from could be useful to scientists in the future who want to innovate in agriculture, pharmaceuticals, or to produce other plant-based products, says Stuart Thompson, a senior lecturer in plant biochemistry at the University of Westminster.

Large seed banks, like the Svalbard Global Seed Vault in Norway, contain many seeds from agricultural crops, as the world's population is currently at about 7.5 billion and is expected to continue rising quickly. With many mouths to feed, Dr. Thompson says, scientists may need to breed new genetics into agricultural crop species to make them more resilient or more productive. But if key genetic diversity is lost, that won't be possible.

Furthermore, he adds, "we could potentially be making use of non-agricultural species to facilitate agricultural innovation." As such, scientists might not know what plant species should be preserved. Some inedible plant could perhaps contain the genetics to revolutionize agriculture, but researchers need its genetics to be able to figure that out.

In that sense, the potential benefits of preserving a species is immeasurable. And so, day in and day out, Perlman heads for the cliffs, following his intuition and clues offered by the natural world to save as many species as he can access.

As a young botanist, Perlman noticed that goats and other grazers that were ravaging Hawaiian plants couldn't reach the steepest cliffs. He surmised that those cliff faces might harbor some of the islands’ rarest species. And so Perlman and his field partner Kenneth Wood have become pioneers of extreme exploratory botany, armed with deep reverence for every species they encounter – and little regard for their own safety.

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“I'm not really thinking that I'm going to be dying because I'm on the cliffs,” Perlman says.

For him, saving plant species is all about responsibility. “I don't want to lose any of these species that are unique and so beautiful,” he says. “It's part of my responsibility to try and keep them all alive.”