Epistemology of exotic deer control.
Veltman, Clare 1, Allen, Rob2, Allen, Will2, Barker, Richard3, Bellingham, Peter2, Forsyth, David4, Jacobson, Chris2, Nicol, Simon4, Richardson, S2, Todd, Charles4, 1 Department of Conservation, Palmerston North, New Zealand2 Landcare Research NZ Ltd, Lincoln, New Zealand3 University of Otago, Dunedin, New Zealand4 Arthur Rylah Institute for Environmental Research, Melbourne, Victoria, Australia
ABSTRACT- Deer have been present in New Zealand forests for almost 150 years. Changes attributed to deer include reduced densities of palatable plant populations, increased densities of unpalatable plant populations and reduced abundance of some soil invertebrates. The formal test of whether these effects can be reversed has been limited so far to measuring differences between small fenced and unfenced plots, in which deer density is either zero or present. We are investigating whether effects of reducing deer density that are predicted from plot-scale results are observed at an operational scale of approximately 4,000 ha in four forests (block-scale), using an adaptive management framework. In scaling up we face spatial heterogeneity in application of the treatment (aerial and ground shooting) that means deer density is a response variable rather than the independent variable. Additionally, the plant sampling needed to detect differences between treated and untreated blocks is not obvious, so we reviewed the range of effects measured at plot scale to provide starting points for predictions. The four forests differ in deer species and plant communities, raising the question of whether they are replicates or cases. Designs that minimise confounding effects of other mammals carried little conviction with some stakeholders. These four early challenges show that testing predictions at a management scale is not equivalent to a scaled-up experiment and may not measure up to the epistemological standard of repeatability. On the credit side, managers value the development of site-specific models and the opportunity for constructive debate in the future based on better knowledge of each site.
Key words: adaptive management, deer, pest control, restoration
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