At the moment we are living in the sixth wave of mass extinctions. The last one 65 million years ago is well-known to have been caused by an asteroid collision (and possible some other factors), after which non-avian dinosaurs became extinct. Currently animal species are disappearing at a rate of 100-1000 times faster than in normal situations. Climate change, habitat loss, pollution and overexploitation are considered the main reasons for this loss, and all of these are human-driven phenomenon. Climate change is a controversial subject, but nevertheless, we are already seeing the effects of it in our co-animals.
Let’s make a short overview of the changes that current climate warming has caused to natural systems. Some changes are direct, but there are also some more complex traits. Climate change-driven impacts are found to work through population abundance, species distributions, morphology and behavior, and eventually impacting community structures.
It is possible that the polar bear, at least as we know the species, will disappear due to climate warming. In the future it might still be possible to see white polar bears in zoos, such as Ranua Zoo in Finland.
Where will the habitats shift?
Habitat shifting is one of the most obvious effects of climate change. It does not just mean moving pole-wards, but also upwards. The Edith’s Checkerspot, a North American butterfly species, has shifted its range both northward (92 km) and upward (by 124 m). During this same time period the temperature isotherms shifted 105 km northwards and 105 m upwards, which corresponds well with the butterfly’s range shift.
The habitat of some animals is not shifting, but disappearing. The arctic ice cover is becoming thinner and ice time is becoming shorter. Icy landscapes are the habitat that polar bears are adapted to. When summers grow longer, polar bears need to spend longer times on land or swimming in the sea. The future of polar bears seems gloomy, and it is expected that the majority of the bears will be lost during coming decades.
In stark contrast to the polar bears, some animals are able to utilize the new areas formed due to the lost ice. In Europe, wintering duck numbers have increased in northern waterbodies, while concurrently decreasing in southern and western parts of Europe. Some areas that were previously avoided because of their hostile winter climate are now used, for example Steller’s eiders (Polysticta stelleri) can nowadays winter in the ice-free parts of the Russian White Sea instead of the Baltic Sea.
Temperature mixes biology
Puffin food catching is becoming difficult because of climate change.
Some species are decreasing, because climate change can crucially affect their breeding success. Vulnerable sea ecosystems have already been shown to be responding to the warming climate. The breeding time of the Atlantic puffin (Fratercula arctica) is usually dependent on North Atlantic Oscillation, except that the effects disappear during certain years. It is expected that this connection is lost due to climate change, possibly via its effect on the availability of the puffins’ fish prey. Researchers suggest that there might be climate-induced changes in the availability of their prey species. Warm sea surface temperatures have also been found to crash the breeding success of tufted puffins (F. cirrhata). Even though they can adjust their breeding phenology according to water temperature, prolonged warm seasons affect the fledging production of this sensitive species and can make their southern breeding habitats unsuitable for them.
Several bird species are known to have changed their phenology during the last decades: since 1937 31% of bird species in Britain, and 53% since 1939, have been found to show long-term trends of breeding earlier. At the same time, only one species has delayed its breeding. The same breeding pattern has been found in Finnish duck species. Ducks have also delayed their autumn migration during the last three decades. In addition, some amphibian species are breeding earlier in Britain now than 30 years ago.
Many natural systems are adapted to working in certain temperatures. If they are disrupted, there will be consequences. For example, the sex of many reptiles is determined by temperature. All the offspring of turtles develop into females in a warm climate, and into males in a cooler climate. Changes in temperatures affect their sex ratio, and a warming of 2 degrees C could make their populations highly female-skewed.
Climate warming releases diseases
Climate change can also affect the sensitive disease balance. Amphibian populations all over the world have been in drastic decline during the last few decades. One of the causes seems to be a deadly fungus, chytridiomycosis. What is extremely worrying, is that the fungus needs a warm climate, and due to climate change, epidemics can occur in new areas. The fungus has so far caused an extinction of at least 93 amphibian species, and is threating amphibian species globally.
Amphibian species all over the world are threatened by a new fungus.
In the hope of evolution
The changes seen now are so rapid that it is unclear how well animal populations, at least long-living ones, can adapt to the new circumstances. But if possible, natural selection could make the polar bears return to their roots, and begin behaving like brown bears again. Or, after seeing a document on polar bears spending their summers swimming and hunting walruses, one could speculate that polar bears could evolve into a true marine species, if there were enough time. Could we also trust evolution to change the limiting temperatures of turtle sex determination? However, all this is speculation, and requires that climate change does not progress too rapidly for long-living species. Models suggest that populations with temperature-dependent sex determination may be unable to evolve rapidly enough. There is a threat that we will lose species such as the polar bears and turtles, unless we play some more time for them by slowing down climate warming.
Can the polar bear become the brown again? Salt, an albino brown bear in Polar park Norway.
REPORT Regime shifts in the breeding of an Atlantic puffin population
Climate change and temperature-dependent sex determination in reptiles
Tufted puffin reproduction reveals ocean climate variability
Climate Extremes: Observations, Modeling, and Impacts