Assessing the ecological suitability of the Irish landscape for the Eurasian lynx
Student Spotlight - Colin Guilfoyle
Masters research carried out at Atlantic Technological University Galway – supervised by Ryan Wilson-Parr and Dr. Joanne O’Brien
Email: cguilfoyle5@gmail.com Twitter: @c_guilfoyle1
Introduction
The Eurasian lynx (Lynx lynx) is a medium-sized felid, which primarily inhabits forested areas and preys mainly on small ungulates like roe deer (Capreolus capreolus) (von Arx et al., 2004). The species is thought to have been indigenous to Ireland during the Holocene period, with one source of fossil evidence dating lynx presence in Ireland to ~9000 years ago (Woodman et al., 1997). Lynx populations have been recovering across Europe and Asia after range declines that occurred up until the 20th century (von Arx et al., 2004), but any natural recolonisation of Ireland is impossible due to its isolation as an island.
There are, however, obligations for both the Republic and Northern Ireland to explore the possibility of reintroducing extinct species, such as the lynx, under the EU Habitats Directive (EEC 1992) and UN Convention on Biological Diversity (Convention on Biological Diversity 1992). There has also been a growing public interest in rewilding and the application of predator reintroduction to aid in the control of a growing Irish deer population.
So, does Ireland have enough habitat to support Eurasian lynx once again? This is the question I had the pleasure of exploring during my MSc research at Atlantic Technological University, where I was supervised by Ryan Wilson-Parr and Dr. Joanne O’Brien.
What we did
Our study first applied a rule-based habitat suitability model, which had been initially developed to explore lynx reintroduction for Scotland (Hetherington et al., 2008), to determine where suitable habitat patches exist in Ireland. Habitat patches were formed by applying rules which took into account the ecological requirements of lynx (mainly the need for large areas with high woodland cover).
Subsequently, we determined the connectivity between habitat patches using a least cost path analysis and estimated the number of lynx that the habitat patches could support, using natural lynx densities seen in Europe (in the absence of Irish deer population data). The final part of the analysis used a modelling software called Rangeshifter, to assess whether a population of lynx could persist in Ireland over 100 years in the current available habitat, and in an increased forest cover scenario.
How much habitat is there and how well connected is it?
The results of the habitat suitability model showed that there is currently 4,488 km2 of suitable lynx habitat distributed across 33 habitat patches, 22 of which were medium sized (74-549 km2), while 11 were small (45-73 km2) in size (Figure 1A). The habitat patches exist in 4 habitat networks and 3 isolated patches, as shown by the least cost path analysis (Figure 1B). The largest habitat network can be found in the southwest of Ireland, covering a total area of 2,723.3 km2, potentially capable of supporting between 8 and 87 lynx at carrying capacity, based on estimates using European lynx densities.
But is this enough to support a self-sustaining population in the long term?
The population viability analysis showed that, under current habitat availability in Ireland, a lynx population would be unlikely to persist in the long term. Simulations were run at different densities (low, medium, and high) and initiated with populations in each habitat patch at carrying capacity. Low- and medium-density simulations had a 100% extinction probability after 20 and 55 years, respectively, while the high-density population had only a 1% chance of persistence after 100 years. Increasing forest cover to 18% only had a considerable effect on the persistence chances of the high-density simulation, with a 63% chance of persistence after 100 years (see Figure 2 below).
Conclusions
Overall, the study indicated that for a lynx reintroduction in Ireland to be successful, there would need to be a considerable increase in forest cover, as well as a large improvement in forest connectivity. While there is scope to improve the accuracy of the analyses in the study through use of forthcoming high resolution land cover and prey density data, the study contributes significantly to the evidence-base surrounding lynx reintroduction debates in Ireland and, in general, highlights the importance of carrying out feasibility studies prior to any reintroduction attempts.
The full paper, which was published in Mammal Research in January, can be found here. Feel free to get in touch via email or Twitter if you have any questions.
Thanks for reading!
References
Convention on Biological Diversity (1992) Rio De Janeiro. Available at: https://www.cbd.int/convention/articles/?a=cbd-09.
European Commission (EEC) (1992) Council Directive 92/43 CEE on the conservation of natural habitats and of wild fauna and fora. European Community Gazette 206:1–50
Hetherington DA, Miller DR, Macleod CD, Gorman ML (2008) A potential habitat network for the Eurasian lynx Lynx lynx in Scotland. Mammal Rev 38(4):285–303. https://doi.org/10.1111/j.1365-2907.2008.00117.x
von Arx M, Breitenmoser-Würsten C, Zimmermann F, Breitenmoser U (2004) Status and conservation of the Eurasian lynx (Lynx lynx) in Europe in 2001. KORA Bericht no. 19
Woodman P, McCarthy M, Monaghan N (1997) The Irish quaternary fauna project. Quatern Sci Rev 16:129–159. https://doi.org/10.1016/S0277-3791(96)00037-6