Another chapter of my PhD has been completed with a peer-reviewed publication in the pipelines. It is a collaboration with Dr Victoria Hemming, Dr Yung En Chee, Dr Anca Hanea and Professor Brendan Wintle. It is about how we can predict effects of management actions on biodiversity, in a spatially explicit way, when key habitat variables are not spatially explicit. Outputs from this approach can inform decision-makers about which actions (or action-sets) are likely to be best for individual species at a site and regional scale, and can serve as an important preliminary step to a regional spatial prioritisation for planning and strategy development.
Effective biodiversity conservation requires robust and transparent methods for cost-effective prioritisation of management actions. However, such prioritisations are often hampered by a lack of empirical data on the effect of management actions and spatially-explicit data on habitat variables. Approaches exist that integrate structured expert elicitation (SEE) with species distribution models (SDMs) to predict species responses across habitat gradients. However, difficulties remain in predicting region-wide management outcomes when key habitat covariates are not spatially explicit. Yet, SDMs built with species occurrence and environmental data (albeit, lacking key habitat variables) are often readily available. Therefore, we developed an approach to integrate SDMs with SEE to a) improve understanding of likely outcomes of management actions for frogs; and b) enable spatial prediction of management effects for multiple species when data is incomplete.
We demonstrate our approach across approximately 4000 wetlands in greater Melbourne, Victoria, Australia. As a measure of management effectiveness, we used the difference in predicted probability of occupancy of seven frog species at wetlands 10 years after conservation actions are implemented (or not implemented). Management effect was elicited from experts under do-nothing and five alternative action scenarios. Individual expert estimates were aggregated using generalised linear models that were used to spatially predict expected management effects, and a measure of uncertainty in the prediction, at all wetlands.
Analyses showed that predicted action effect was influenced by species initial occupancy. In our case, enhancing aquatic vegetation, along with surrounding vegetation, was a key action for most species. We demonstrate a straightforward approach to predicting management effects over large spatial areas when data is incomplete by augmenting information from SDMs with SEE. This approach offers insight for decision-makers on how to understand and maximise benefit across species on a wetland and regional scale while minimising risks of negative effects.
A lot has happened since I posted my original post many moons ago. I had a baby and went on maternity leave for starters. Upon returning I started a collaboration with Geoff Heard, Brendan Wintle and Yung En Chee on exploring the common problem: how should we choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? We tackled this through linking population viability analysis (PVA) with a cost-effectiveness analysis (CEA) and found that no one had adequately accounted for uncertainty in such an integration. Our relatively straightforward method combines the simplicity of a CEA with the sophistication of a metapopulation model. An overview is given below and the full publication (Rose et al. 2016) can be found here.
The most satisfying outcome from this work is that it has had a real influence on the decisions made by key decision-makers involved in the case study. Both Melbourne Water and the Victorian Government have read the work and contacted me on advice about how to modify plans in the area so that our findings are taken into account. This gives the endangered growling grass frog a far greater chance of persistence in the developing zone. It also highlights the importance of strengthening networks and sharing knowledge between practitioner’s, government and academia. In addition to publication of the findings, direct communication with Melbourne Water at the beginning and end of the study (e.g. discussions and a presentation) drove changes in decision-making.
Growling grass frog. Photo by Geoff Heard
Cost- effective conservation under uncertainty: study overview
Well-developed tools exist for prioritizing areas for one-time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost-effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost-effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost-effectiveness analysis. This allowed us to discern between cost-effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost-effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost-effective action likely to result in a sufficiently low risk of extinction in this case. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost-effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost-effective conservation under uncertainty.
For my research I’m interested in improving the quality of decisions in management and conservation of wetlands by exploring quantitative tools for prioritization of resource allocation. I will consider different wetland types and multiple wetland species and functional groups.
Today’s focus, however, is the growling grass frog (Litoria raniformis) on the urban fringe of Melbourne.