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

Bare Ground

Water

Pasture

Gorse

Narrow-leaved Scrub

Regenerating Forest

Indigenous Forest

Exotic Forest

Unspecified Woody

EcoSat Basic Landcover

Indigenous Forest Composition

“Carrying Capacity” = potential possum density (in absence of control)

Possum TB model – patchy habitat

Possum TB Model (5x5 km)

Bare Ground

Water

Pasture

Narrow-leaved Scrub

Regenerating Forest

Indigenous Forest

Exotic Forest

Unspecified Woody

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

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

NPM – Web demonstration

Discussion• End-user requirements, ideas

– typical control scenarios– density / RTC thresholds

• Potential problems, data sensitivities• Cost – free?

Photo by Morgan Coleman