Get access

Effects of species and habitat positional errors on the performance and interpretation of species distribution models

Authors

  • Patrick E. Osborne,

    Corresponding author
    1. Centre for Environmental Sciences, School of Civil Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK
    Search for more papers by this author
  • Pedro J. Leitão

    1. Centre for Environmental Sciences, School of Civil Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK
    2. Centro de Ecologia Aplicada ‘Prof. Baeta Neves’, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
    Search for more papers by this author
    • Present address: Abteilung Geoinformatik, Geographisches Institut, Humboldt-Universität zu Berlin, Rudower Chaussee 16, 12489 Berlin-Adlershof, Germany.


*Patrick E. Osborne, Centre for Environmental Sciences, School of Civil Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
E-mail: p.e.osborne@soton.ac.uk

Abstract

Aim  A key assumption in species distribution modelling is that both species and environmental data layers contain no positional errors, yet this will rarely be true. This study assesses the effect of introduced positional errors on the performance and interpretation of species distribution models.

Location  Baixo Alentejo region of Portugal.

Methods  Data on steppe bird occurrence were collected using a random stratified sampling design on a 1-km2 pixel grid. Environmental data were sourced from satellite imagery and digital maps. Error was deliberately introduced into the species data as shifts in a random direction of 0–1, 2–3, 4–5 and 0–5 pixels. Whole habitat layers were shifted by 1 pixel to cause mis-registration, and the cumulative effect of one to three shifted layers investigated. Distribution models were built for three species using three algorithms with three replicates. Test models were compared with controls without errors.

Results  Positional errors in the species data led to a drop in model performance (larger errors having larger effects – typically up to 10% drop in area under the curve on average), although not enough for models to be rejected. Model interpretation was more severely affected with inconsistencies in the contributing variables. Errors in the habitat layers had similar although lesser effects.

Main conclusions  Models with species positional errors are hard to detect, often statistically good, ecologically plausible and useful for prediction, but interpreting them is dangerous. Mis-registered habitat layers produce smaller effects probably because shifting entire layers does not break down the correlation structure to the same extent as random shifts in individual species observations. Spatial autocorrelation in the habitat layers may protect against species positional errors to some extent but the relationship is complex and requires further work. The key recommendation must be that positional errors should be minimised through careful field design and data processing.

Ancillary