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How many possums and where? The National Possum Model. James Shepherd & Mandy Barron. How many possums in NZ?. (A = 30.3 million). How many possums? Who cares?. It’s how possums distributed in space and how their numbers change through time that is important. Possum control decisions.
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How many possums and where?The National Possum Model James Shepherd & Mandy Barron
How many possums in NZ? (A = 30.3 million)
How many possums? Who cares? It’s how possums distributed in space and how their numbers change through time that is important
Possum control decisions • When? (timing and frequency) • Where? (site prioritisation) • Need to know current (and predicted) state of possum populations across your sites to make these decisions
LCR possum-TB model • LCR currently has a useful individual-based possum model that runs at local operational scales • Also models bovine tuberculosis (TB) within possum population • Can assess effect of management regimes on possums and TB by simulating possum control • Possum abundance in model is determined by habitat carrying capacity
“Carrying Capacity” = potential possum density (in absence of control)
Scaling up to the national level • Context is important • National Possum Model (NPM), national coverage – high spatial detail • all of the information we would use in a local simulation but NZ-wide! • millions of individuals! • Not just a static map – dynamic and interactive model • web input & output • online delivery of present and future population projections
NPM −Why do we want to do this? • LCR is a national institute, efficient for us to provide a single national predictive tool to land managers – demonstrate our research • Because we can… spatially-detailed vegetation, ecological, climate and soil layers all exist at national scale AND we now have the computing power
NPM −Why do we want to do this? • Would provide a central integration point for possum control information • essential for accurate predictions • Integrating the datasets & technology required for NPM would provide a framework for other pest species such as rats & goats
NPM −Why do we want to do this? • Web delivery would provide easy user access to present and future pest densities and disease prevalence information • Potential for the public to see an overview showing control effort and impact (compared with “no control” scenario)
NPM −How would we do this? • Re-write possum-TB model code, processing distributed amongst a 100 CPU cluster • Integrate and adapt national layers for vegetation to provide base data to assign carrying capacity • LCDB 1 & 2 (3) • Kyoto forestry maps 1990 & 2008 (2012) • EcoSat BLC & indigenous forest classes
NPM −How would we do this? • Streamline model input for users to integrate their own control information (area, date and RTC) • Continue underpinning ecological research • Relationship between land cover & pest density • Improve model parameters such as home range distribution, dispersal, probability of disease transmission
NPM −How would we do this? • Provide user feedback to the underlying science when model predictions differ from reality • Focus future science effort Photo by Paul Horton
NPM −Results / Output No Control
NPM −Results / Output post AHB & DOC control in 2008/09
Discussion • End-user requirements, ideas • typical control scenarios • density / RTC thresholds • Potential problems, data sensitivities • Cost – free? Photo by Morgan Coleman