Landscape Ecology

, Volume 22, Issue 8, pp 1155–1168 | Cite as

Testing assumptions of cost surface analysis—a tool for invasive species management

  • Emily K. GonzalesEmail author
  • Sarah E. Gergel
Research Article


Applied ecology could benefit from new tools that identify potential movement pathways of invasive species, particularly where data are sparse. Cost surface analysis (CSA) estimates the permeability (friction) across a landscape and can be applied to dispersal modelling. Increasingly used in a diversity of applications, several fundamental assumptions that might influence the outputs of CSA (cost surfaces and least-cost pathways) have yet to be systematically examined. Thus, we explore two issues: the presumed relationship between habitat preferences and dispersal behaviour as well as the degree of landscape fragmentation through which an organism moves by modelling a total of 18 sensitivity and dispersal scenarios. We explored the effect of fragmentation by altering the friction values (generally assigned using expert opinion) associated with patch and linear features. We compared these sensitivity scenarios in two sites that differed in fragmentation. We also used eastern grey squirrels (Sciurus carolinensis) as an example invading species and compared diffusion models and two contrasting cost surface dispersal scenarios. The diffusion model underestimated spread because squirrels did not move randomly through the landscape. Despite contrasting assumptions regarding dispersal behaviour, the two cost surfaces were strikingly similar while the least-cost paths differed. Furthermore, while the cost surfaces were insensitive to changes in friction values for linear features, they were sensitive to assumptions made for patch features. Our results suggest that movement in fragmented landscapes may be more sensitive to assumptions regarding friction values than contiguous landscapes. Thus, the reliability of CSA may depend not only on the range of friction values used for patches but also the degree of contiguity in the landscape.


Canada Dispersal Exotic GIS Least-cost pathway Non-native Sciurus carolinensis Spatial models Squirrel Weighted surface 



Financial support for EKG was provided by a National Science and Engineering Research Council (NSERC) Industrial Postgraduate Scholarship, Pacific Region Environmental Systems Research Institute of Canada, Arthur Richmond Memorial Scholarship Graduate Scholarship at the University of Guelph, and the Mountain Equipment Co-Op Environment Fund. Digital data was generously provided by Geographic Data British Columbia, British Columbia Ministry of Environment, Land and Parks, Greater Vancouver Regional District, and Crown Lands Registry Services. EKG greatly appreciates the intellectual support from Dr. Tom Nudds and Dr. Peter Arcese. Thank you to the survey respondents, many of whom submitted interesting stories. We are grateful to Jessie Hui-Chung Wu, Janelle Curtis, Thorsten Wiegand, Patrick Lilley, and the anonymous reviewers who made improvements to earlier versions of the manuscript.


  1. Adriaensen F, Chardon JP, De Blust G, Swinnen E, Villalba S, Gulinck H, Matthysen E (2003) The application of ‘least-cost’ modelling as a functional landscape model. Landsc Urban Plan 64:233–247CrossRefGoogle Scholar
  2. Allen LJS, Allen EJ, Kunst CRG, Sosebee RE (1991) A diffusion model for spread of Opuntia imbricata (cholla) on rangeland. J Ecol 79:1123–1135CrossRefGoogle Scholar
  3. Andow DA, Kareiva PM, Levin SA, Okubo A (1990) Spread of invading organisms. Landsc Ecol 4:177–188CrossRefGoogle Scholar
  4. Bunn AG, Urban DL, Keitt TH (2000) Landscape connectivity: a conservation application of graph theory. J Environ Manage 59:265–278CrossRefGoogle Scholar
  5. Collischonn W, Pilar JV (2000) A direction dependent least-cost-path algorithm for roads and canals. Int J Geogr Inf Sci 14:397–406CrossRefGoogle Scholar
  6. Doak DF, Mills LS (1994) A useful role for theory in conservation. Ecology 75:615–626CrossRefGoogle Scholar
  7. Douglas DH (1994) Least-cost path in GIS using an accumulated weighted surface and slope lines. Cartographica 31:37–51Google Scholar
  8. Dunning JB, Stewart DJ, Danielson BJ, Noon BR, Root TL, Lamberson RH, Stevens EE (1995) Spatially explicit population-models—current forms and future uses. Ecol Appl 5(1):3–11CrossRefGoogle Scholar
  9. Feldman SC, Pelletier RE, Walser E, Smoot JC, Ahl D (1995) A prototype for pipeline routing using remotely sensed data and geographic information system analysis. Remote Sens Environ 53:123–131CrossRefGoogle Scholar
  10. Ferreras P (2001) Landscape structure and asymmetrical inter-patch connectivity in a metapopulation of the endangered Iberian lynx. Biol Conserv 100:125–136CrossRefGoogle Scholar
  11. Foody, GM (2006) What is the difference between two maps? A remote senser's view. J Geogr Syst 8(2):119–130CrossRefGoogle Scholar
  12. Foody GM (2002) Status of land cover classification accuracy assessment. Remote Sens Environ 80:185–201CrossRefGoogle Scholar
  13. Gergel SE (2007) New directions in landscape pattern analysis and linkages with remote sensing. In: Wulder MA, Franklin SE (eds) Remote sensing spatial pattern. Taylor & Francis—CRC PressGoogle Scholar
  14. Gonzales EK (2005) The distribution and habitat selection of introduced eastern grey squirrels (Sciurus carolinensis) in British Columbia. Can Field Nat 119:343–350Google Scholar
  15. Gonzales EK (1999) The grey squirrel in British Columbia: an introduction to an introduction. Discovery 28:22–25Google Scholar
  16. Guiguet CJ (1975) An introduction of the grey squirrel on Vancouver Island. Syesis 8:399Google Scholar
  17. Gurnell J (1987) The natural history of squirrels. Christopher Helm, London, UKGoogle Scholar
  18. Gurnell J, Wauters LA, Lurz PWW, Tosi G (2004) Alien species and interspecific competition: effects of introduced eastern grey squirrels on red squirrel population dynamics. J Anim Ecol 73:26–35CrossRefGoogle Scholar
  19. Hagen A (2003) Fuzzy set approach to assessing similarity of categorical maps. Int J Geogr Inf Sci 17(3):235–249CrossRefGoogle Scholar
  20. Hagen-Zanker A (2006) Comparing continuous valued raster data: a cross disciplinary literature scan. Research Institute for Knowledge Systems. Maastricht, The NetherlandsGoogle Scholar
  21. Hastings A, Cuddington K, Davies KF, Dugaw CJ, Elmendorf S, Freestone A, Harrison S, Holland M, Lambrinos J, Malvadkar U, Melbourne BA, Moore K, Taylor C, Thomson D (2005) The spatial spread of invasions: new developments in theory and evidence. Ecol Lett 8(1):91–101CrossRefGoogle Scholar
  22. Hengeveld R (1994) Small step invasion research. Trends Ecol Evol 9:339–342CrossRefGoogle Scholar
  23. Hwang Y (2005) A test of interspecific effects of Eastern Grey Squirrels on Douglas's squirrels in Vancouver, British Columbia. Canadian Field Naturalist 119 (in press)Google Scholar
  24. Jaeger JAG, Bowman J, Brennan J, Fahrig L, Bert D, Bouchard J, Charbonneau N, Frank K, Gruber B, von Toschanowitz KT (2005) Predicting when animal populations are at risk from roads: an interactive model of road avoidance behaviour. Ecological Modell 185:329–348CrossRefGoogle Scholar
  25. Kenward RE, Parish T (1986) Bark-stripping by gray squirrels (Sciurus carolinensis). J Zool 210:473–481CrossRefGoogle Scholar
  26. Kramer-Schadt S, Revilla E, Wiegand T, Breitenmoser U (2004) Fragmented landscapes, road mortality and patch connectivity: modelling influences on the dispersal of Eurasian lynx. J Appl Ecol 41:711–723CrossRefGoogle Scholar
  27. Lurz PWW, Rushton SP, Wauters LA, Bertolino S, Currado I, Mazzoglio P, Shirley MDF (2001) Predicting grey squirrel expansion in north Italy: a spatially explicit modelling approach. Landsc Ecol 16:407–420CrossRefGoogle Scholar
  28. Lurz PWW, Geddes N, Lloyd AJ, Shirley MDE, Rushton SP, Burlton B (2003) Planning a red squirrel conservation area: using a spatially explicit population dynamics model to predict the impact of felling and forest design plans. Forestry 76:95–108CrossRefGoogle Scholar
  29. Mack RN, Simberloff D, Lonsdale WM, Evans H, Clout M, Bazzaz, FA (2000) Biotic invasions: causes, epidemiology, global consequences, and control. Ecol Appl 10:689–710CrossRefGoogle Scholar
  30. Manly BFJ, McDonald LL, Thomas DL, McDonald TL, Erikson WP (2002) Resource selection by animals: statistical design and analysis for field studies, 2nd edn. Kluwer Academic Publishers, Dordrecht, the NetherlandsGoogle Scholar
  31. Middleton AD (1930) The ecology of the American gray squirrel (Sciurus carolinensis Gmelin) in the British Isles. Proc Zool Soc Lond 2:809–843Google Scholar
  32. Mountford EP (1997) A decade of grey squirrel bark stripping damage to beech in Lady Park wood, UK. Forestry 70:17–29CrossRefGoogle Scholar
  33. Myers JA, Vellend M, Gardescu S, Marks PL (2004) Seed spread by white-tailed deer: implications for long-distance spread, invasion, and migration of plants in eastern North America. Oecologia 139:35–44PubMedCrossRefGoogle Scholar
  34. Nathan R, Perry G, Cronin JT, Strand AE, Cain ML (2003) Methods for estimating long-distance dispersal. Oikos 103:261–273CrossRefGoogle Scholar
  35. Nikolakaki P (2004) A GIS site-selection process for habitat creation: estimating connectivity of habitat patches. Landsc Urban Plan 68:77–94CrossRefGoogle Scholar
  36. Ó Teangana D, Reilly R, Montgomery WI, Rochford J (2000) Distribution and status of the red squirrel (Sciurus vulgaris) and grey squirrel (Sciurus carolinensis) in Ireland. Mammal Rev 30:45–56CrossRefGoogle Scholar
  37. Okubo A, Maini PK, Williamson MH, Murray JD (1989) On the spatial spread of the grey squirrel in Britain. Proc R Soc Lond 238:113–125CrossRefPubMedGoogle Scholar
  38. Palomares F (2001) Vegetation structure and prey abundance requirements of the Iberian lynx: implications for the design of reserves and corridors. J Appl Ecol 38(1):9–18CrossRefGoogle Scholar
  39. Pimentel D, Lach L, Zuniga R, Morrison D (2000) Environmental and economic costs of nonindigenous species in the United States. BioScience 50:53–64CrossRefGoogle Scholar
  40. Power C, Simms A, White R (2001) Hierarchical fuzzy pattern matching for the regional comparison of land use maps. Int J Geogr Inf Sci 15(1):77–100CrossRefGoogle Scholar
  41. Pysek P, Hulme PE (2005) Spatio-temporal dynamics of plant invasions: linking pattern to process. Ecoscience 12:302–315CrossRefGoogle Scholar
  42. Ray N, Lehmann A, Joly P (2002) Modelling spatial distribution of amphibian populations: a GIS approach based on habitat matrix permeability. Biodivers Conserv 11:2143–2165CrossRefGoogle Scholar
  43. Rejmánek M, Pitcairn MJ (2002) When is eradication of exotic pest plants a realistic goal? In: Veitch D, Clout M (eds) Turning the tide: eradication of invasive species. Invasive Species Specialist Group of the World Conservation Union (IUCN). Gland, Switzerland and Cambridge, UK, pp 249–253Google Scholar
  44. Revilla E, Wiegand T, Palomares F, Ferreras P, Delibes M (2004) Effects of matrix heterogeneity on animal dispersal: from individual behavior to metapopulation-level parameters. Am Nat 164(5):E130–E153PubMedCrossRefGoogle Scholar
  45. Reynolds JC (1985) Details of the geographic replacement of the red squirrel (Sciurus vulgaris) by the grey squirrel (Sciurus carolinensis) in eastern England. J Anim Ecol 54:149–162CrossRefGoogle Scholar
  46. Robinson DJ, McTaggart-Cowan I (1954) An invasive population of the Gray Squirrel (Sciurus carolinensis Gmelin) in British Columbia. Can J Zool 32:261–282CrossRefGoogle Scholar
  47. Ruckelshaus M, Hartway C, Kareiva P (1997) Assessing the data requirements of spatially explicit dispersal models. Conserv Biol 11(6):1298-1306CrossRefGoogle Scholar
  48. Sharov AA (2004) Bioeconomics of managing the spread of exotic pest species with barrier zones. Risk Anal 24:879–892PubMedCrossRefGoogle Scholar
  49. Sheail J (1999) The grey squirrel (Sciurus carolinensis)—a UK historical perspective on a vertebrate pest species. J Environ Manage 55:145–156CrossRefGoogle Scholar
  50. Shigesada N, Kawasaki K, Takeda Y (1995) Modelling stratified diffusion in biological invasions. Am Nat 146:229–251CrossRefGoogle Scholar
  51. Shorten M (1957) Squirrels in England, Wales and Scotland, 1955. J Anim Ecol 26:287–294CrossRefGoogle Scholar
  52. Simberloff D (2003) How much information on population biology is needed to manage introduced species? Conserv Biol 17:83–92CrossRefGoogle Scholar
  53. Skellam JG (1951) Random spread in theoretical populations. Biometrika 38:286–308Google Scholar
  54. Suarez AV, Holway DA, Case TJ (2001) Patterns of spread in biological invasions dominated by long-distance jump spread: insights from argentine ants. Proc Nat Acad Sci USA 98:1095–1100PubMedCrossRefGoogle Scholar
  55. Verbeylen G, De Bruyn L, Adriaensen F, Matthysen E (2003) Does matrix resistance influence red squirrel (Sciurus vulgaris L. 1758) distribution in an urban landscape? Landsc Ecol 76:95–108Google Scholar
  56. Visser H, de Nijs T (2006) The Map Comparison Kit. Environ Modell Softw 21(3): 346–358CrossRefGoogle Scholar
  57. Wauters L, Gurnell J, Currado I, Mazzoglio PJ (1997) Grey squirrel Sciurus carolinensis management in Italy—squirrel distribution in a highly fragmented landscape. Wildl Biol 3:117–124Google Scholar
  58. Zollner PA, Lima SL (2005) Behavioral tradeoffs when dispersing across a patchy landscape. Oikos 108(2):219–230CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  1. 1.Integrative BiologyUniversity of GuelphGuelphCanada
  2. 2.Forest Sciences, Centre for Applied Conservation Research University of British ColumbiaVancouverCanada

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