Just how far should we go to save the last of a species? Jeffrey A McNeely, the chief scientist at IUCN-The World Conservation Union, argues in this week's Green Room that even a little effort can reap huge reward.
Hiking through the vast Wollemi National Park in Australia's Blue Mountains in 1994, David Noble stumbled upon a hidden rainforest gorge.
The actions of conservationists to save extremely rare species could be compared to the heroic feats of physicians to keep their patients alive as long as possible
As a National Parks and Wildlife Officer, Noble quickly recognised that this tiny patch of habitat was very special indeed.
The isolated gorge contained less than 100 mature trees of a species that had long been thought extinct, with fossils stretching back 90 million years.
Now known as the Wollemi pine, it was found to be closely related to the monkey puzzle tree.
Noble's dilemma was whether to simply keep walking and let nature take the tree on its inevitable course towards extinction, or to trumpet this major discovery to the outside world, with the danger that plant fanciers would flock to the gorge and "love the tree to death" by accidentally bringing in new species or diseases.
Or should some of the trees be removed from the wild and put in captivity, where they could be carefully nurtured and protected against any remaining threat?
The latter could prove to be extremely expensive, but to what end?
Conservationists face these kinds of dilemmas on a regular basis.
One of the strongest arguments for conservation is that every species has a role to play in the great drama of life. But once a species has been reduced to only a handful of individuals, surely the show can go on without these bit players.
After all, we have already lost over 99% of the species that have ever existed, due mainly to natural causes.
So why should we spend our scarce resources to conserve species that are down to their last gasp?
The actions of conservationists to save extremely rare species could be compared to the heroic feats of physicians to keep their patients alive as long as possible.
What portion of a country's health budget should be spent for keeping healthy people healthy, and how much should go to prolonging a life that is already nearing its end?
In the US, for example, about 30% of Medicare's $250bn annual budget is spent on the terminally ill.
Others can debate the ethical and economic issues of human health budgets, but the point here is to ask whether spending, for instance, $40m to save the last 22 California condors might have been better spent on species with a higher probability of longer-term survival.
But this investment has led to the recovery of the California condor to the extent that it is now being reintroduced to its habitat of thousands of years ago, in the Grand Canyon in Arizona.
A key consideration is that a species is not truly extinct until the last one is gone.
Species that are down to their last few individuals are capable of making a remarkable recovery, either on their own or with a little help from their human friends.
As another example, the Arabian oryx was teetering on the verge of extinction when captive breeding steadily multiplied the herd to a sufficient size that some could be re-introduced to establish a wild population in Oman and, one hopes, Saudi Arabia in the near future.
Rhinos, whooping cranes, and black-footed ferrets have similar stories of conservation action leading to recovery.
Who would question the value of conserving the rhino?
Some have suggested that conservationists should resign themselves to becoming historians of extinctions rather than soldiers in what might seem a doomed conservation battle.
Yet the many examples of bringing species back from the brink demonstrate that once we know that a species is in trouble, it can often be saved - if we are willing to make the necessary investments.
The Wollemi pine shows that human ingenuity can find solutions to conservation challenges.
First, the remote rainforest home of the Wollemi pine was declared off limits except to National Parks and Wildlife staff.
Second, a mass propagation project in a well-protected nursery has produced hundreds of saplings, a reproduction rate far higher than would be seen in the Australian bush.
Even better, their rarity has given them such an outstanding value that when the first available captive-bred Wollemi pines were put on auction at Sotheby's in October 2005, they reportedly earned over US$1m. Sotheby's Chairman, Justin Millar, stated, "These are really, I'd have to say, up there amongst the most exciting things I've ever sold."
A portion of the funds earned was returned to conserving the remaining trees. And a whole new lucrative industry of captive breeding of this species has been generated in Australia.
This is a remarkable success story for one of the rarest trees in the world, a relic from the time of the dinosaurs that was saved from the brink of extinction and is now earning a healthy income.
It provides a vivid example of why we should invest in saving the last of a species.
After all, we seem to have no problem spending billions of dollars on developing more effective means of destroying each other, let alone prolonging the lives of the terminally ill.
Why not spend the relatively modest amounts needed to help to save the diversity of life on Planet Earth?
Jeffrey A McNeely is the chief scientist at IUCN-The World Conservation Union.
The IUCN brings government and non-government organisations, and thousands of scientists into a global network for conservation. It publishes the famous Red List of Threatened Species.
The Green Room is a series of opinion articles on environmental issues running weekly on the BBC News website.