Will penguins that can't keep up with climate change "disappear"?

 　　The penguin, which can be called a "smart swimmer" and a "master diver", has been born on the earth for more than 60 million years. Before becoming a master in the water, it also has the ability to fly.

　　On July 19, an international study published online by Nature Communications, a journal of the Nature Publishing Group, gave a detailed evolutionary history of penguins from flight to sea adaptation. By constructing a genome dataset of 24 extant penguin species, including subspecies, and 3 recently extinct penguin species, the research team combined the genome data of extant penguin and recently extinct penguin lineages with the complete fossil record for the first time to reconstruct the penguin's ancestry. Evolutionary history and determine which genes contributed to the transition of penguins to aquatic animals.

　　Penguins are among the slowest-evolving species of birds for which genome-wide data has been obtained, which may make it difficult for them to adapt to the current rate of global warming, research shows. Daniel Kesepka, a co-author of the study and an avian paleontologist at the Bruce Museum, wrote in an email to China News Weekly, "It has been seen from the fossil record that penguins can adapt to cooling or warming, but The problem is that adaptation often takes tens of thousands or even millions of years. Most species, including penguins, may not have enough time to adapt if rapid global warming continues over the next few decades."

　　

One of the slowest evolving birds

　　Wings turned into flippers, a streamlined body, long dives, a chubby body... These features make modern penguins look less like birds, but help them better adapt to sea life and cold climates. From a long-term perspective, penguins have not stopped evolving for tens of millions of years. With changes in geological, climate, environmental and other factors, the modern penguins we see today are formed. In the study in Nature Communications, the researchers gave a "full picture" of penguin evolution.

　　Research shows that more than 60 million years ago, penguin ancestors appeared in the ancient Zealand region, which is now the New Zealand mainland, and then spread from ancient Zealand to South America and Antarctica. The Antarctic ice sheet formed 34 million years ago, during which many giant penguins were differentiated. The most recent penguin species diversification began 2 million years ago during the Quaternary Great Ice Age, during which global temperatures cooled dramatically, and large-scale ice sheets and mountain glaciers were widely formed in middle and high latitudes, including polar regions and high mountains. Expanding ice caps and environmental changes prompted penguins to begin migrating to wider areas, gradually becoming isolated from each other, leading to the rapid divergence of multiple extant penguin species.

　　Zhou Chengran, the co-first author of the paper and an associate researcher at the Shenzhen BGI Life Sciences Research Institute, told China News Weekly that judging from the oldest penguin fossils found in the current study, the penguin wings at that time may still have the function of folding, but they could no longer fly. . The earliest penguin ancestor may have evolved from a flying puffin, Kseepka said, and since the former has not been found in the fossil record, it is impossible to know exactly when penguins lost their ability to fly.

　　The study's corresponding author, Zhang Guojie, a professor at the Life Evolution Research Center of Zhejiang University, told China News Weekly that species differentiation is often accompanied by complex gene flow, which makes penguin morphology more diverse. According to the International Union for Conservation of Nature (IUCN), there are currently 18 recognized penguin species, including emperor penguins, Adelie penguins, Humboldt penguins, and yellow-eyed penguins. Different populations of penguins are also distributed in the vast areas of the southern hemisphere such as Australia and New Zealand.

　　"During the long evolution, penguins have evolved a set of 'genetic secrets' to adapt to the environment. They have related evolutionary genes in thermoregulation, oxygen, diving, vision, body shape, etc., shaping penguins into what they are today and making them more Fortunately, the cold environment and underwater life." Zhou Chengran told China News Weekly.

　　Compared with the early penguins, the living penguins gradually tend to be smaller in size, the beaks used to obtain food become shorter, and the flipper-like forelimbs evolved from wings are more suitable for the marine environment. Zhou Chengran said that in terms of taste, penguins only retain the perception of sour and salty tastes, and have lost the genes related to fresh, sweet and bitter tastes. Research speculates that when eating in the cold ocean, the loss of the latter tastes is important to them. Has little effect.

　　A variety of genetic mutations also make penguins have strong ultraviolet perception, visual sensitivity, etc., and can maintain sharp vision even in low light or dim seawater. "The frequency of light irradiation in seawater is significantly different from that on land. If penguins do not evolve themselves, long-term exposure to seawater will cause their eyesight to be damaged." Zhang Guojie said.

　　There are also differences in the ability of different penguin species to snorkel in seawater. Zhou Chengran gave an example. In terms of diving time and depth, emperor penguins have the strongest diving ability among all penguins. They can dive for about 30 minutes in the deep sea area of ​​more than 500 meters. Most of the little blue penguins can only dive for a few minutes at most. "In addition to genetic reasons, this difference is also affected by penguin habitat environment and food resources. For example, little blue penguins generally choose nearshore places to catch food, and little blue penguins are smaller than emperor penguins, and their food intake is relatively small. "she says.

Daniel Kesepka believes that the earliest penguin ancestors may have evolved from a flying puffin. Figure/Visual China

　　Today, penguins have developed an adaptive relationship with their habitat. For example, emperor penguins and Adelie penguins also live in Antarctica. The former chooses to go to a certain area on the ice sheet in winter to incubate the next generation. They reach the Antarctic coastline for breeding in spring and summer, when the glaciers in some areas begin to melt, the brown rocks on the ground are exposed, and the color of Adélie penguin chicks is brownish.

　　It is worth mentioning that the study also compared the genome data of penguins with more than 360 non-penguin birds, and found that penguins and their relatives, albatrosses, have the slowest evolution rate. Kesepka believes this may be related to factors such as above-average lifespan and low numbers of offspring. "It was surprising to discover this, because penguins and other bird groups have no significant differences in body size and breeding time. We did not expect penguins to evolve so much slower than other birds." Zhang Guojie told China News Weekly. Zhou Chengran recalled, "After finding this result at that time, I compared other data and found that the evolution rate of aquatic birds that are more closely related is lower than that of non-aquatic birds. Therefore, it is speculated that the reason may also be related to the aquatic characteristics of water birds. "

　　From the perspective of the evolution rate of penguins, there is no significant correlation between body weight and evolution speed, but the study found that the largest emperor penguin living in high latitudes has the fastest evolution rate among all penguins." The extreme environment of Antarctica has brought greater environmental pressure to high-latitude penguins. Environmental events such as glacial periods and climate fluctuations further promoted the migration, evolution and differentiation of penguins, which to a certain extent promoted the adaptation of high-latitude species to extreme environments. "The speciation of penguins is largely driven by global climate change, geological movements, etc.," the study noted.

Global warming, will penguins become "extinct" in the future?

　　"The slow evolution rate of penguins may mean that they need to adapt to the environment and climate change for a longer time." In Zhou Chengran's view, although penguins have developed a strong adaptation to marine life and the Antarctic environment, this "strong" "Fitness" is based on time units of millions of years, and the time span over which significant global warming is currently monitored has been shortened to the past 100 to 300 years. Whether penguins can quickly adapt to climate change, and whether there is a serious threat to their future survival, are all matters of concern.

　　The Antarctic Peninsula is one of the fastest-warming regions on Earth, with a rise of 3°C over the past 50 years, World Meteorological Organization Secretary-General Petiri Talas said in 2021. In May, Taalas said the past seven years had been the seven warmest on record, with "the warmest year on record" ahead. "In general, the average temperature of the entire Antarctic is rising rapidly." Li Xichen, a researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, told China News Weekly that the temperature rise varies in different regions. Some sites also experienced explosive warming, although shorter and less impactful, the extremes are becoming more frequent.

　　According to penguin information statistics released by the International Union for Conservation of Nature, more than 40% of the world's penguins currently live in Antarctica. Zhang Guojie analyzed that irregular temperature changes in Antarctica may have a greater impact on penguin reproduction, such as difficulty in hatching; in addition, it may also have an impact on the surrounding food structure, thereby affecting penguin migration routes and habitats.

　　The most direct result of global warming is the accelerated melting of glaciers. According to the Intergovernmental Panel of Experts on Climate Change (IPCC) data, from 1990 to 2022, the two largest ice sheets in the world, Greenland and Antarctica, have been melting, with the highest loss rate between 2010 and 2019. NASA satellite data shows that Antarctica has been losing ice at an average rate of about 150 billion tons a year since 2003, while Greenland has lost about 280 billion tons a year.

　　Li Xichen said that in the past ten years, the melting rate of the entire Antarctic glaciers has accelerated by at least three times. "If the temperature continues to increase, the rate of melting of Antarctic glaciers may further increase in the future." He worries that, compared with the previous slow melting of the glaciers, there may be a risk of "collapse" melting of the West Antarctic glaciers at some point in the future. "If the entire West Antarctic glaciers melt, the global sea level will rise by at least 6 to 7 meters. This will cause a great crisis, and many places may face the fate of being 'flooded'."

　　The survival of penguins is closely related to glaciers. The sea ice breeds, rests and moults, and the penguins' food, krill, also thrives near the edge of the ice. Emperor penguins try to return to the same place to breed every winter, and if temperatures continue to rise, it will be difficult to find stable, long-lasting ice to nurture their offspring, Kesepka said. In 2016, about 10,000 little emperor penguins in Antarctica's Halley Bay, one of the largest breeding grounds for emperor penguins, were drowned because the sea ice broke before the little penguins could grow feathers, The Associated Press reported. In 2017 and 2018, almost all of the little emperor penguins in this area died during each breeding season of the two years because the sea ice did not fully recover. Since then, Halley Bay has seen almost no emperor penguins, while nearby Dawson Langton has seen a marked increase in the number of emperor penguins.

　　The aforementioned "Nature Communications" study pointed out that the evolution rate of modern penguins has become lower than that of ancestor penguins. When exposed to the climate background of global warming, its survival status does not seem optimistic. "About three-quarters of the currently known penguin species are extinct," Kesepka said. "China News Weekly" inquired about the red list of the International Union for Conservation of Nature and found that among the 18 existing penguin species, the population of 12 penguins has declined, and a total of 11 species have been identified as endangered, near-threatened or vulnerable. accounted for more than 60%. Among them, yellow-eyed penguins, African penguins, straight-top penguins, northern rockhopper penguins, and Galapagos penguins are endangered, and the number of mature individuals of Galapagos penguins has been reduced to 1,200.

In 2019, some biological fossils were unearthed in New Zealand. Based on these fossils, it is speculated that about 66 million years ago, a giant penguin with a height of 160 cm and a weight of 80 kg once inhabited New Zealand.

　　"It seems that the situation is still relatively serious." Zhou Chengran said that most of these endangered penguins do not live in the Antarctic continent, but live in Africa, New Zealand and other places. Populations in these places are more susceptible to anthropogenic factors, which, coupled with climate warming and habitat loss, have made existing populations less stable. Most of the three extinct penguins involved in the study, published in Nature Communications, died out based on these factors. The three extinct penguins are Chatham Island penguins, Chatham Island yellow-eyed penguins and Waitaha penguins, all of which have previously lived in New Zealand.

　　Not all penguin species experience population declines as the climate warms. "There are differences in the responses of different penguin species to climate change, which may be related to their different life histories." Zhang Guojie believes.

　　From 1982 to 2017, as temperatures rose, the breeding population of gentoo penguins on the West Antarctic Peninsula jumped from 25,000 to 173,000, Scientific American reported in July 2019. Gentoo penguins are known to be mainly found on the Antarctic Peninsula, the Falkland Islands and South Georgia, and as the ice melts, they adjust their food types and expand their range, such as shifting from hunting krill to fish. For food, gentoo penguins can swim at up to 22 miles per hour and dive deeper, while Adélie penguins rely on floating sea ice for food. Yan Denghui, a member of China's 38th Antarctic expedition team, told China News Weekly that the decrease in the number of penguins does not mean that these penguins are extinct. It may be because the penguins choose to migrate to colder high latitudes after the local temperature rises. Settlement, which takes at least decades to monitor and track.

　　In Li Chenxi's view, despite the "Antarctic Treaty" and other protection measures, it is difficult for Antarctica to be alone when exposed to a global environment full of carbon emissions, aerosol particles and other pollutants. Zhang Guojie said, don't be too pessimistic, most penguins are not endangered species, and penguins themselves will have a coordination mechanism when facing environmental changes.

　　But in Zhou Chengran's view, based on various risk factors, some penguin species may face extinction in the future. "The drastic changes in climate may also be beyond their tolerance to some extent. For the penguins themselves, this may spur them to the next evolutionary cycle, or some species will face extinction."