Accounting for the interactions between management actions
Threatened plants and animals often face multiple threats, each of which require different management actions. Because we're dealing with a connected system, actions over here create reactions over there; in other words management actions interact and those interactions can either amplify other threatening processes or, conversely, ameliorate the impacts of other threats.
For instance, more than one pest may need controlling in some areas of the landscape, so we don't create a worse situation. If both foxes and rabbits have invaded a particular area in Australia, controlling rabbits alone may lead to foxes preying more on native animals, while controlling foxes alone may result in a flourishing rabbit population.
Alternatively, reducing the effects of several threats by managing only one may also be possible. For example, many Australian mammals are vulnerable in degraded habitat, including having no escape from invasive, predatory cats. If we restore habitat with suitable refuges, perhaps investing in difficult and expensive cat control will be less important.
To reduce costs, we can also consider interactions in choosing where we manage. When neighbouring landowners choose to cooperatively prevent the spread of weeds, they are opting to reduce a threat in connected areas. This could result in an overall cost reduction in managing weeds across the landscape.
The best strategy would account for the interactions between management actions. Managing for species complementarity is a good example where interaction is taken into account in conservation planning. The value of protecting species in one area depends upon what other areas have already been protected. In effect, the whole strategy of our protective action is worth more than the sum of its parts, and this enhances efficiency.
One way we can select which actions we take first is to look at what economists do. Given that we have a limited budget, we can use cost-effectiveness analysis to find where we could act to get the best return on our investment. The cost effectiveness of taking conservation action in a specific location is calculated by dividing the amount of expected good we can do by the cost of doing the action.
By using this cost-effectiveness ratio to compare between different locations and combinations of management actions, we can find where we are likely to achieve the greatest benefit for our money.
Our research finds that threatened species management that disregards interactions between actions may lead to misplaced investments or misguided expectations of the effort required to reduce threats to species. Alternatively, explicitly accounting for interactions between threat management actions may lead to better guidance in choosing where we can more efficiently act to protect our threatened species.