The biggest bang for our conservation buck
Scientists are using mathematical formulae normally used by economists and engineers to work out which of the world's biodiversity hotspots to save first.
Since the 1980s, global conservation agencies have identified particular areas around the world that are rich in species but under threat from habitat destruction.
But there are many such 'biodiversity hotspots' that need attention, and a limited budget to save them.
Until now, says Possingham, there hasn't been a rational way of prioritising where to act first.
"Do you act in them all simultaneously? Do you try and pick out three of them? And how long do you spend acting in one before you move to another?"
Possingham's team has applied mathematical tools regularly used by economists and engineers to find the optimum way to answer these questions.
"[The tools] run our entire economy, they schedule all the airlines, they schedule all the trains," says Possingham.
"Any transportation organisation is using optimisation methods to work out which trucks should go where at what times."
He says in this case the tools are applied to saving as many species as possible.
"In a sense it's not that much more than third year or fourth year applied maths or economics at university," says Possingham.
"But the kind of people working in these [conservation] fields often don't have these skills so they often thought about formulating the problem properly."
Possingham's team has developed a method of prioritising hotspots that take into consideration a range of features apart from how many species an area has.
High priority is given to areas where habitat is fast disappearing, little of the area has already disappeared, and where the cost of conserving habitat is low.
Another factor that influences the priority given to an area is how likely it is to conserved in the future.
"If you are going to invest in a place where you're not sure that you'll get the investment, you're not sure the national park will stay a national park, you'd want to get a lot more benefit out of that investment," says Possingham.
"You're willing to pay higher prices for places that are secure."
He says this is exactly the same as trade-offs made in the share market, where you expect a higher outcome for high-risk investments and a lower outcome for low-risk ones.
So far Possingham and team have tested their method on five areas in South East Asia and found that Sulawesi would be a higher priority than Sumatra, Borneo, Java and Malaysia.