Modelling the Dynamics of Translocated Populations

Abstract

Climate change is widely accepted as one of the worst threat to the world’s biodiversity. A recently proposed solution to help species survive climate change is “assisted colonisation”, i.e. translocations of species to more suitable sites. Although assisted colonisation could be a powerful conservation tool, translocations are known to have a low success rate despite being commonly-used. Before promoting assisted colonisation as a solution, we need to make two major advances: first, understand how translocated species will respond to a changing climate and if their population viability will be compromised and, second, develop a quantitative framework to improve the success rates of conservation translocation under global environmental change. Those were the two aims of my thesis. The hihi (stitchbird; Notiomystis cincta ) was used as a study species. It has been the subject of several translocations in the past few decades and every translocated population is intensely monitored, yielding long-term demographic datasets. Climate was found to be a key factor in the dynamics of translocated population, and thus viability. However, it may also interact with other intrinsic factors like density and age to influence species’ long-term persistence. A stochastic population model built to quantify the potential impacts of future climate change on translocated populations’ long-term persistence showed the importance of taking into account the impact of longer and more frequent extreme weather on translocated population’s viability. Moreover, MaxEnt was found to be a good habitat suitability model for translocated populations and used to identify future translocation sites for the hihi under climate change. Finally, quantitative guidelines for the planning and implementation of assisted colonisations were developed. They address the known issues impeding translocation success, and, if used, will maximise the success of assisted colonisations.