Accounting for the interactions between management actions
- threatened species face multiple threats that need managing
- effective management requires a consideration of how management actions for different threats might act together
- considering management interactions when choosing conservation priorities is not common
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.
Choosing where we manage
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.
In all three cases (foxes and rabbits; cats and degraded habitat; and weeds in multiple locations), 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.
Unfortunately, taking interactions like this into account is not common. Generally, effects of management interactions are not well understood. Therefore it could be worth thinking about how to create integrated management strategies that take other interactions between management actions into consideration.
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.
Evidence suggests that we can be more efficient with an integrated strategy, as compared to managing threats independently. What hasn’t been made clear is how we can make our money go further by targeting management that includes interactions, and what happens when we do this at a regional level, where most managers work. A better understanding about the effects of management interactions could lead to better conservation outcomes.
In sum, 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.
More info: Nancy Auerbach email@example.com
Auerbach NA, KA Wilson, AIT Tulloch, JR Rhodes, JO Hanson & HP Possingham (2015). Effects of threat management interactions on conservation priorities. Conservation Biology 29:1626-1635. DOI: 10.1111/cobi.12551.
Modelling costs and benefits in the Burnett-Mary Region
Our case study of a biodiverse region of southeastern Queensland (the Burnett-Mary Natural Resource Management Region) quantified how locations chosen for action, investment needed, and benefits expected differed when management interactions were taken into account (Auerbach et al, 2015). Threatening processes (for threatened species) included habitat degradation by domestic stock, fires that are too frequent and intense, and predation by the red fox.
To quantify the cost of reducing threats across the landscape, we modeled the costs of decreasing grazing pressure, managing fire for biodiversity, and controlling foxes. We based our cost models on factors such as lost agricultural profit if stock are removed from an area, differing expenses of managing fire in peri-urban and rural areas, and wages for setting bait stations (fox control) at varied distances from roads.
We created species distribution models to determine where we thought habitat would exist for the threatened species in our study area, and overlaid these maps to determine where more and fewer species were likely to have suitable habitat. To quantify the benefit we expect to receive from our three management actions at each site, we made the assumption that if we take action in a site where we think one, or a set of, threatened species is likely to have suitable habitat, those species would receive benefit from our action. We next calculated the cost-effectiveness of taking each action, and each combination of actions, by dividing the expected benefit by its cost. Finally, we ranked each site-by-action combination from high to low cost-effectiveness value, so we could order where and which set of threats we would choose to work on, given a budget limit.
We mapped cost-effective management locations when each species benefitted 1) when we managed only one of their threats, 2) when we managed only all of their threats, or 3) when we disregarded interactions. In comparing these maps, we discovered that when we managed for interactions, our decisions about where to invest, and in which actions to invest, were different than when interactions were not considered. The expected management benefit for the same amount of money was also different in these three approaches.
Next, we mapped cost-effective management locations for one threat 4) when costs were reduced in sites close to management sites previously chosen, and compared this to 5) when we didn’t account for locational interactions. We found that we could manage more compact areas for less money by accounting for interactions. However, we note that habitat fragmentation may limit the effectiveness of particular management actions, and restoration may also need consideration as an additional action.