How are some animals and plants responding to a warming world? Dr Anjani Ganase looks at some creatures’ adaptations to survive the changing climate.
We are in the anthropocene – the current geological era where human activities have significant impacts on the environment and climate. Indeed, humans are currently driving the sixth mass extinction. To date we are losing species to extinction at a rate of about 2,000 species every year (WWF est.). While many die off, other animals and plants are undergoing adaptation to survive either the warming conditions directly or changes in habitat conditions, food supply and environment. Scientists who have been monitoring and conducting genetic studies over the last 50 years have been able to match changes in animal physiology (body shape and size) or behaviour (migratory timing) to changes in temperature. There are a few creatures that do benefit from the warmer conditions, although the extent of such benefits remain to be seen in the future. Here are some examples of adaptations by creatures to their environment brought on by climate change.
Upgrading your buddy
Symbiosis refers to two organisms living together for their survival. Corals are known to have symbiont algae living in their tissues that provide food from photosynthesis, while the corals provide the algae with nutrients and remove waste. Unfortunately, the algae can be sensitive to warm conditions which results in coral bleaching. Scientists have observed that corals present on reefs with a history of frequent coral bleaching because of thermal stress appear to be less sensitive to subsequent bleaching because the coral host has swapped out their symbiotic algae for a more heat-tolerant variety that makes the coral more resistant to future warming events. Some scientists are even breeding these heat-tolerant strains to develop super corals able to withstand climate change and plant them out on the reef. Many of these strategies are done at a very small scale and for a handful of coral species.
Changing their timing
Scientists have observed that populations of pink salmon in Alaska returning to Auke Creek in Juneau for spawning arrive in two waves. Dark-coloured salmon arrived as early migrators in August, while brightly-coloured salmon would arrive in the late wave in September. Over time, scientists have observed significant shifts in the proportion of early and late migrators, and found later migrators reduced in their populations. Today, the average migration time for pink salmon to more upstream for spawning is about two weeks earlier compared to 40 years ago. Scientists also found that the early migrators were able to cope with warmer summer temperatures better than the late migrators.
The movements of about 26 species of commercial fish species in the Pacific, including salmon, herring, sharks, and sardines have been tracked over the years. Researchers found that patterns in fish movement have shifted northward, away from the warming tropical waters at a rate of about 25 miles every ten years. The shift in the movement away from the warm water does not necessarily improve their survival as some of the habitats they move towards are not suitable feeding grounds.
More versatile eating
By looking at the historical fossil records of grey whales, scientists have determined that grey whales are somewhat flexible in their feeding behaviour as a way to survive. Today, most Pacific grey whales have migrated from Baja California to the cold nutrient-rich waters of Alaska to feed on plankton by skimming the surface of the water in shallow water habitats. However, when scientists looked back to the last ice age (120,000 years ago), when sea level was much lower than it is today, they found that the habitats that they would feed in today were mostly absent.
By looking at the habitat shift in the grey whales during that time, they theorised that grey whales must have been versatile feeders to survive. Such versatility is observed today, as a pod making up one per cent of the grey whale population in the Pacific have stopped the migratory routes, which was primarily driven by hunting in the recent times. Now they have become resident off the coast of Vancouver year-round with a different feeding style to the migrators. This gives scientists some insight into the possibilities for adapting to climate change.
Shape and colour shifting
According to Allen’s law for a body’s thermo-regulation (adapting to temperature), the length of the appendages relative to body size tends to be bigger in warmer environments. This allows organisms to shed excess heat by radiating through the thin appendages such as ears, tails and wings. In colder climates, animals tend to be bigger, reducing their surface areas to volume ratio (Bergmann’s rule) to reduce heat loss. Therefore, it has been predicted that animals would become more adapted to the heat by having longer appendages to body size. For birds, including Australian parrots and the Galapagos finches, scientists have observed an increase in their bill sizes with warmer climates. For mammals such as wood mice, shrews and bats, all show an increase in longer tails, wings and ears in warmer environments. Such adaptations are expected for climate change and have been observed in some instances. However, it is still difficult to predict as many other factors play a role in the shifting climate conditions such as habitat and food availability, and disease.
Benefitting from the warmth
In Europe, milder, shorter winters have boosted the population of tawny owls as their brown plumage allows them to camouflage better year-round. Conversely, snowy owls with white and grey feathers are not faring as well. Finally, thyme, which is adapted to the dry Mediterranean weather, has expanded its range in Europe, also because of milder winters.
It is still very much up in the air whether adaptations improve survival in the long term, as there may be other consequences to such changes in temperature. We can only hope that we do enough to slow the global warming rate to facilitate the adaptation and survival of more creatures. We can also boost nature’s ability to adapt to climate change by limiting the amount of other disturbance impacts caused by human activities. Pollution and land clearing for example, on top of climate change, make it very difficult for species to survive the onslaught of impacts. By protecting areas and regulating impacts, we can let nature evolve and allow organisms to be more resilient to climate change.
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