Researchers from Macquarie University have been studying geckos (Gehyra variegata) in arid areas of Australia to determine the impacts of climate change and the possible responses of gecko populations.
The pace of the change in climate expected over the next 70 years is greater than any other change in climate in human history. Even with effective climate policy and major changes in greenhouse gas emissions the world over there is still a significant possibility of exceeding a 2 degree temperature increase that will have major negative impact on ecosystems.
Increases in global average temperature, changes in rainfall patterns and more extreme events (such as drought, fire, flood and cyclones) are the major factors that all organisms on earth potentially have to face. Each of these factors will have differing levels of impacts so the actual changes in climate and ecosystems will differ between areas.
Animals have an advantage over plants when it comes to adapting to and coping with climate change as they can move to new areas. To achieve a 1 degree temperature change an animal needs to move 100m upwards in altitude or 125km south (in the southern hemisphere or north in the northern hemisphere). This means that to combat a 2 degree temperature rise a shift of 250km would be required if a mountainous habitat was not suitable or available (and Australia is a very flat country – 99% percent of the continent is <1000m above sea level).
Paul Duckett and other scientists from Macquarie University used models to identify suitable habitats for the geckos and what proportion would make it to these new habitats. A startling conclusion they came to was that although there are places for the geckos to move to which would mitigate the effects of climate change the problem would be in them actually getting there.
The modeling showed that over 40% of the gecko populations would not reach suitable areas before climate change has negative impacts on the populations, such as small population sizes and the associated genetic consequences. There are also suitable areas to colonise that won’t be used as the geckos won’t be able to migrate that far within the time span of the change in climate.
As the data used in these models is based on past conditions it is possible that the rates of gecko dispersal may differ from the model under actual climate change conditions. For example, the geckos in the past may have dispersed under specific rainfall and aridity conditions, but these may not be the same conditions under which the geckos will disperse in times of climate change as the Australian continent is expected to experience increasing aridity. In addition the predicted future distribution of these geckos is expected to overlap with areas utilised by humans, so fragmented environments may have additional impacts on the persistance of gecko populations.
And even if the geckos do make it to their new and suitable habitats far to the south of their current locations what is the chance that their food source also made the journey successfully?
Duckett PE, Wilson PD, Stow AJ (2013). Keeping up with the neighbours: using a genetic measurement of dispersal and species distribution modelling to assess the impact of climate change on an Australian arid zone gecko (Gehyra variegata). Diversity and Distributions, DOI: 10.1111/ddi.12071