Evolving in a Changing World

Climate change is causing temperatures to rise, but what does this actually mean for the various species and populations of the world? Organisms have always had to respond to naturally occurring climate change. However, anthropogenic greenhouse emissions are prompting changes in environmental factors - not just temperature, but also factors such as rainfall and ocean acidity  - at a rate and scale of change far above what would have occurred naturally. Consequently, there is a considerable amount of concern regarding whether natural populations can respond fast enough to ‘keep up’ with this increased rate of change.

Encouragingly, we’re seeing some species respond to climate change through migration. Natural populations, including species of insects, birds, mammals, plants, fish and marine invertebrates, have shifted their range poleward towards cooler areas of higher latitude.  

Australian species of sea urchins are among those shifting their distribution poleward in recent years. Photo: Peter Southwood (Wiki Commons)

Australian species of sea urchins are among those shifting their distribution poleward in recent years. Photo: Peter Southwood (Wiki Commons)

Unfortunately, migration is more challenging for some species than others. Many have poor dispersal abilities and others lack any suitable alternative habitat to disperse to. The latter is especially an issue for those that are specialised to small or sporadically distributed habitats, such as high altitude alpine areas. The ability of natural populations to migrate has also been severely hampered by habitat fragmentation and the construction of human-made structures, including cities and roads, which may act as barriers to migration. 

Natural populations in which migration is not a sufficient solution to adapting to the effects of climate change must either adapt or face extinction. While factors such as temperature are expected to shift beyond what many natural populations can currently tolerate, groups of animals may have the capacity to respond to these changes by undergoing adaptive evolution.

Evolution involves changes in a population’s genetic make-up from one generation to the next. In the case of adaptive evolution to climate change, these genetic changes over multiple generations may facilitate changes in traits, such as thermo-tolerance, that can allow populations to mitigate the effects of climate change. 

Although evolution is frequently perceived as a laboriously slow process, this is often not the case. Evolution can be rapid, especially for species with short lifetimes. For instance, an ecologically important species of phytoplankton was shown in an experimental study to significantly improve its performance under increased levels of ocean acidity in less than a year of adaptive evolution. We are also seeing evidence of populations being able to adaptively evolve to the effects of climate change through studies on natural populations. One example of this is the Canadian Red Squirrel, that has adapted to seasonal changes in food availability by giving birth to offspring earlier in Spring when more food is available.

Some species, such as the Canadian red squirrel, have shown an evolutionary response to the effects of climate change. Photo: Gilles Gonthier (Wiki Commons)

Some species, such as the Canadian red squirrel, have shown an evolutionary response to the effects of climate change. Photo: Gilles Gonthier (Wiki Commons)

However, it is far from all good news. Some populations have been found to possess worryingly limited potential to adapt to climate change. In tropical Queensland, populations of fruit flies have very little ability to improve their resistance to lower levels of environmental humidity, which are predicted to occur with future climate change. While I can certainly see how the possible extinction of a fly species might sound like fantastic news to some, such results in any natural population are troubling. Furthermore, even if a population has the capacity to adapt to current rates of climate change, this does not guarantee that they will be able to continue to evolve fast enough to keep up with changes in the future. 

Continued research is crucially important. Photo: Evatt Chirgwin

Continued research is crucially important. Photo: Evatt Chirgwin

Evolution is likely to have an enormous role in determining which species and populations can adapt to long-term climate change, and as such needs to be considered by natural resource managers. Through incorporating evolutionary processes into their management strategies to counter climate change, these managers can create more efficient methods of protecting biodiversity. For instance, identifying species of low evolutionary potential can assist them in identifying which species are of high vulnerability to extinction from climate change. 

Importantly, natural resource managers need to employ strategies to safeguard against loosing the existing evolutionary capacity held by natural populations. Though this is often easier said than done, the best way to protect a population’s ability to adapt is by maintaining a large population size. The larger a population, the more likely it is to to maintain high levels of genetic diversity, and the less likely it is to loose beneficial genes that could confer a greater ability for adaptation to climate change.

Additionally, management can protect the evolutionary capacity of species by sustaining connectivity between populations through habitat preservation or establishment of artificial wildlife corridors. Connectivity can allow genes that are beneficial for adaption to spread more easily through multiple populations. Alternately, if natural links are not possible, it may be appropriate in some circumstances for individuals to be artificially moved between populations of the same species to aid the spread of beneficial genetic information.

Increasing population connectivity can aid the movement of beneficial genes between populations. Photo: Krd (Wiki Commons)

Increasing population connectivity can aid the movement of beneficial genes between populations. Photo: Krd (Wiki Commons)

Despite the potential of these and several other possible strategies to reduce the effects of climate change on biodiversity, most simply treat the symptoms of the problem and not the problem itself. The most effective strategy in protecting biodiversity is to reduce anthropogenic greenhouse emissions as greatly and as quickly as possible, so that our planet’s range of amazingly diverse species have a better chance to survive.

Cover photo taken by Allison Chirgwin.