Numerus PVA

An interactive Population Viability Analysis web app for single and multi-populations.

An educational example:

  Wolves on Isle Royale

Generic rhino example:

  Illustrative Rhino PVA

Enter model parameters through the following methods:

Recommended for first time users, this option will walk users through entering the model parameters as a self-guided tour.

This option allows users to manually enter parameters at the population, movement, and stocking and harvesting levels.

Intended for experienced users, this option allows users to tweak model parameters locally and directly import to model.

Interact with the model through dynamic and interactive population structure

Here we present a versatile, extensible web application to carry out harvesting, stocking, and node-to-node transitions within a PVA framework. Built using the Nova Modeling engine, this website can be used to dynamically create a meta- (or multi-) Population Viability Analysis (PVA) model with user-interactivity. We will use the acronyms SPVA & MPVA to differentiate between single-population and multi-population PVA.

Users can specify an array of conditions for the model at the demographic, environmental, and meta-population scale. Stochasticity is included both as demographic (e.g. small population size effects) and environmental (e.g. driving variable fluctuations drawn from climatic variable distributions), with the former being critical to carrying out species extinction risk analyses (i.e. PVA) and the latter permits possible climate trend information to be accounded for in multi-decadal simulations. When in deterministic mode - i.e. when demographic stochasticity is set off and environmental stochasticity is set to 0.0 - is the most useful when evaluating various management strategies implemented in large populations. Generally this occurs in the context of sustainable fisheries or forestry exploitation rates that are optimal in some sense.

Intuitive design

Extensible model features

Export as local CSV

Model Overview easily transition from SPVA to MPVA

At the simplest level, one can choose to run the engine in deterministic mode for a single-sex, homogeneous population with no density dependence. At its most complex, one can run the engine in two-sex, density-dependent, meta-population mode, with both demographic and environmental stochasticity. Both situations (and any level of complexity between) is set by user-specifications as region and age-class based parameters. The particular mode and parameters used within model runs are invoked through an array of input forms / fields, check-box options, and interactive sliders.

As mentioned above, the model can be ran as a SPVA or as a MPVA. If the meta-population option is invoked, the model will consist of M homogeneous subpopulations connected by a natural movement proclivity matrix. The movement of individuals is determined by both this movement matrix and a proposensity for individuals of different ages to move (e.g. only maturing males in search of territory may move, and so on). This is illustrated in the two figures: showing movement propensities at the age-class and region levels.