Defining landscape resistance values in least-cost connectivity models for the invasive grey squirrel: a comparison of approaches using expert-opinion and habitat suitability modelling.
Least-cost models are widely used to study the functional connectivity of habitat within a varied landscape matrix. A critical step in the process is identifying resistance values for each land cover based upon the facilitating or impeding impact on species movement. Ideally resistance values would be parameterised with empirical data, but due to a shortage of such information, expert-opinion is often used. However, the use of expert-opinion is seen as subjective, human-centric and unreliable. This study derived resistance values from grey squirrel habitat suitability models (HSM) in order to compare the utility and validity of this approach with more traditional, expert-led methods. Models were built and tested with MaxEnt, using squirrel presence records and a categorical land cover map for Cumbria, UK. Predictions on the likelihood of squirrel occurrence within each land cover type were inverted, providing resistance values which were used to parameterise a least-cost model. The resulting habitat networks were measured and compared to those derived from a least-cost model built with previously collated information from experts. The expert-derived and HSM-inferred least-cost networks differ in precision. The HSM-informed networks were smaller and more fragmented because of the higher resistance values attributed to most habitats. These results are discussed in relation to the applicability of both approaches for conservation and management objectives, providing guidance to researchers and practitioners attempting to apply and interpret a least-cost approach to mapping ecological networks.
Centre for Wildlife Conservation, University of Cumbria, Ambleside, Cumbria, United Kingdom.
Claire D
CD
Stevenson-Holt
Centre for Ecosystems, Society and Biosecurity, Forest Research, Farnham, Surrey, United Kingdom.
Kevin
K
Watts
Centre for Ecosystems, Society and Biosecurity, Forest Research, Roslin, Midlothian, United Kingdom.
Chloe C
CC
Bellamy
School of Medical and Applied Sciences, Central Queensland University, Gladstone, Queensland, Australia.
Owen T
OT
Nevin
School of Biological and Forensic Sciences, University of Derby, Derby, Derbyshire, United Kingdom.
Andrew D
AD
Ramsey
D000818:Animals; D003247:Conservation of Natural Resources; D017753:Ecosystem; D058865:Introduced Species / Q000706:statistics & numerical data*; D008962:Models, Theoretical; D012589:Sciuridae