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Making good decisions in multi-species, multi-threat systems

Most species face multiple threats that together play a role in observed species declines.

To reduce or reverse these declines, conservation plans need to allocate management actions across multiple threats and prioritise actions for the threats causing the biggest declines.

However, managers are often faced with the problem of limited knowledge regarding which threats are causing the biggest declines in species and limited resources to manage the threats are prevalent in the system.

They need to not only understand the effect of threats and management actions on species but, given the limited resources, they also need to know how best to obtain this information to make threat management decisions.

Species are commonly monitored to learn about the effect of threats. With multiple species and multiple threats, understanding which species to monitor to enhance our knowledge of the system is not straightforward.

We propose a method using value of information (VOI) analysis to estimate the benefits of monitoring for management decision-making in multi-species, multi-threat systems. The idea is that monitoring influences the management decision and VOI helps evaluate the expected improvement in management outcomes when decisions are taken under additional information (say from monitoring).

We use this approach to compare the benefit of monitoring different species and monitoring using different strategies, e.g. surveillance monitoring (monitoring species without experimentation) to targeted monitoring (monitoring species with experimentation to learn about a specific threat), in systems with multiple threats and species.

We also illustrate our approach using two case studies for monitoring and managing declining mammals in Western Australia.
Case study results for targeted versus surveillance monitoring for the Pilbara (a–d), and Fitz-Stirling (e–h), where targeted monitoring involves experimentally managing one of the two threats. Expected value of sample information is expressed as the reduction in expected number of species declining.

We find that that surveillance monitoring provides less benefits than targeted monitoring, for managing threats under economic constraints in complex systems with multiple threats and species. We also find that the best monitoring strategy can change with the budget available for management, the differential impacts of threats on species and the relative costs of managing the different threats prevalent in the system.

We recommend that managers need to consider a range of factors when selecting which species to monitor to inform management decisions. Our framework provides an objective way to do this.
Our new VOI approach can be used to disentangle the trade-offs in competing monitoring actions so that managers can decide how to invest their money in monitoring actions, or if at all, when faced with imminent biodiversity declines and the urgency or efficient conservation action.
Dr Payal Bal

For more information: Payal Bal, payal.bal@unimelb.edu.au

Credits:

Created with images by RenataWrightArt - "wa western australia outback" • Fabrizio Frigeni - "untitled image" • Aleksandar Jason - "Coastal Kangaroo"

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