By Claire Asher, on 16 May 2014
Climate change alters how climate is distributed both geographically and temporally. Over the coming decades, for species sensitive to climatic variables, it may become a case of ‘relocate or die’ – those species that are not able to shift their populations from old, unsuitable habitat into newly emerging suitable habitat, in line with climate change, will likely go extinct. Conservationists can provide a helping hand to species in this position, however – translocation programs aim to establish populations in appropriate habitat when the species is unlikely to reach it on their own. Determining whether translocations are likely to be necessary in the future, what populations to move and where to move them are complex questions to answer, however. Recent work by researchers at the Institute of Zoology (part of the Center for Ecology and Evolution and affiliated with UCL’s GEE department) developed a framework for understanding species’ relationships with climate and identifying potential translocation sites which will provide suitable habitat through future climate change. For one of New Zealand’s endemic birds, the Hihi, translocation to sites further south may be it’s best chance of long-term survival.
The climate is changing. Changes in temperature, rainfall and seasonality are occurring globally, and we are already measuring the effects on wildlife. Often, conditions are shifting geographically, and many species will find that their current range no longer overlaps with any suitable habitat (human land-use change isn’t helping!). In these cases, some species will be able to shift their ranges to account for this, but many species will be unable to do change quickly enough to keep up and instead face extinction. Humans can intervene here by moving endangered species to more suitable habitat, but translocation is expensive and it is crucial to select the new location carefully if the population is to have a chance of succeeding. IoZ researchers set out to develop a statistical framework for determining suitable translocation habitat, using one of New Zealands most endearing but endangered endemics, the Hihi (Notiomystis cincta), to test the framework.
The population of Hihis in Tiritiri Mantangi island offers a special opportunity to study the direct effects of climate change without other variables such as food ability confounding the results. This is because they have been provided supplementary food for nearly two decades. Using data on the reproductive success of females in this population, combined with climate data, Dr Aliénor Chauvenet and Dr Nathalie Pettorelli from the Institute of Zoology, along with colleagues at Imperial College London and Massey University in New Zealand, were able to show that Hihi populations are effected by the climate even when food availability is removed from the equation.
Next, using mathematical modelling, the authors tried to predict the future of Hihi populations, using different simulated changes in climate based upon the variables that were found to be most important in influencing current Hihi populations on Tiritiri Mantangi. Changes in temperature, as well as increases in climate variability had a significant influence on the survival of simulated Hihi populations. The final step was to again use mathematical modelling to predict and map suitable Hihi habitat both now, and in the future. Again, this modelling showed that current Hihi populations are most strongly influenced by temperature, a key variable in determining habitat suitability, with rainfall as another important influence.
Looking forward, under models of predicted future climate change, suitable Hihi habitat is expected to move south. The north of New Zealand, which currently offers highly suitable habitat, is predicted to become almost entirely unsuitable over the next few decades. The most successful reintroduced population of Hihis, as well as the largest and last remaining natural Hihi population both stand to lose suitable habitat by 2050. New suitable habitat is expected to emerge in the southern end of the North Island, as well as the northern part of the South Island, where historically conditions have not been suitable for Hihis.
Because Hihis show population declines as temperatures warm even when we control for food availability, even careful management of existing population may prove ineffective under future climate change. Instead, translocation may provide the only solution to guarantee the long-term survival of the Hihi in New Zealand. Although translocations traditionally perform the role of reintroduction – returning a species to part of it’s historical range – future plans for endangered species like the Hihi need to take climate change into consideration. We should opt for ‘assisted colonisation’ – introducing populations to new habitat that is likely to persist (and perhaps even become more suitable) through future climate change. In this way we can attempt to ‘future-proof’ our conservation efforts and hopefully ensure the survival of many species which might otherwise go extinct as the climate changes.