Penguins, polar bears and reindeer: why are cold-loving animals not dying out from warming?

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Penguins, polar bears and reindeer: why are cold-loving animals not dying out from warming?
Penguins, polar bears and reindeer: why are cold-loving animals not dying out from warming?
Anonim

For many years we were shown photographs of a polar bear, exhausted beyond recognition, and said that extinction awaits not only them, but also other cold-loving animals. However, a number of scientific works in recent years indicate otherwise: there is no evidence that such animals are actually dying out. A number of indicators show that this is unlikely to happen at all during the current warming. The most numerous penguins of Antarctica have multiplied rapidly due to the retreat of ice. The number of reindeer in the Russian tundra is growing so strongly that it has already become a serious problem with which local authorities do not know what to do. What went wrong in the Greens' calculations? What allows animals that feel normal in the cold not to suffer too much from their retreat? Let's figure it out.

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The life cycle of many cold-loving animals is clearly inscribed in the harsh polar nature. Ursus maritimus (polar bear in Latin is designated "sea") gains weight mainly in the spring, killing and eating white and fluffy seal cubs (they still cannot escape in the water), located right on the sea ice. Well, and adults, if he can watch for them at the "ducts" - a small hole in which seals float up in order to breathe. The seal's claws keep it open even in severe frosts. It seems obvious that without sea ice there will be no seals, no their cubs, no opportunities to watch for them at the gutters.

Here are two ready-made endangered species - and very important ones. After all, the seal is the main mammal of the northern seas, and the polar bear is the largest existing land predator.

The situation with the penguins is no less clear. There will be no ice, their habitual environment will change, they will not be able to survive in new conditions. After all, the cold waters of Antarctica contain a lot of oxygen (the colder the water, the more this gas dissolves in it). Therefore, it is easier to live there for rather large Antarctic krill - crustaceans ranging in length from 1.0 to 6.5 centimeters.

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Reindeer are accustomed to the tundra with its insignificant non-summer precipitation, and more and more of them come there as the climate warms. The frost after the rain forms a crust of ice, which the deer simply cannot overcome, which is why it will die of hunger. Probably the same fate should befall the musk ox and many other typically northern species. Didn't many of the mammals of that time become extinct in the past warming extinction - at the end of the last ice age?

Ironically, all of these seemingly obvious things are wrong. Let's try to figure it out step by step.

Penguins: first fell prey to … a cold snap?

Penguins are a very ancient group of birds, that is, according to today's cladistics, smooth-billed dinosaurs. They definitely existed 60 million years ago, and their oldest remains are recorded in New Zealand. The second most ancient - more than 40 million years ago - in Peru, and the third - in Argentina. It should be remembered: 60 and 30-40 million years ago, the planet was much warmer than today. Even Antarctica was largely free of ice. However, it was in that era that the largest of the penguins lived: the species Anthropornis nordenskjoldi reached 90 kilograms in weight and 1.8 meters in height.

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Penguins from that warm era did not encounter noticeable sea ice very often, and the water off the coast of Antarctica was about as warm as in southern South America today. How did they survive if not so much oxygen was dissolved in the waters near Antarctica as it is now?

To understand this, it is worth taking a close look at modern penguins. Suddenly it turns out that they live - in addition to the ancestral home, New Zealand - in the waters near the four continents. Moreover, only four of the most cold-resistant species live in Antarctica, and the remaining 14 never see it, because they live near Australia, South America and Africa (up to Namibia). Needless to say, it is impossible to call Namibian or Australian penguins truly cold-loving.

And one of the species of these birds does live on the Galapagos Islands - that is, near the equator, at zero degrees of latitude. The air there is warmed up as it should be at the equator, and the water is never colder plus 22 even in the “cold” season (locals call it garúa, “drizzle”). In other words, this is the temperature that is considered normal in swimming pools for humans - primates of African origin.

The conclusion suggests itself: penguins as a whole, as a group, are not like birds, which are threatened with extinction by warming. In the warm past, they were larger than they are today, and large individuals are unlikely to exist where there is a shortage of food.

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Moreover, scientists directly suggest that a cooling of the climate that happened 35 million years ago in the Antarctic region (and globally) could directly destroy the "old" species of giant penguins. There is also genetic evidence for this: an analysis of the genomes of all existing species of these birds shows that they descended from one species - a common ancestor.

The problem is that this species only lived 20 million years ago. Consequently, all other penguin species that existed from 20 to 62 million years ago, simply died without descendant species. At that time, it was a developed and diversified group with a huge range - from Antarctica to Peru. To "kill" all its species, a powerful factor is needed, and a gradual cooling and the formation of a permanent ice sheet on the surface of the southernmost continent is best suited for its role.

And then - warming?

Maybe we are rushing to conclusions, and modern penguins, unlike the ancients, have so adapted to the cold that they can no longer survive without it?

Let's check this thesis. The penguins most adapted to the cold are four Antarctic species. Of these, the most numerous are the Adélie penguins. Do they feel good near the icy expanses of the Antarctic coast and how is global warming affecting them?

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A closer look at the way of life of these birds shows that Adélie penguins are not always happy with the "Antarctic" features of the surrounding landscape in their lives. To hatch their eggs, despite the cool climate, they cover them with dark stones that absorb solar radiation well.

However, Antarctica has a lot of ice, but not enough stones. Therefore, a real battle unfolds for them - power, if you are a male, and sexual, if you are a female. Females approach males from other pairs (during breeding, Adélie penguins form permanent pairs), having access to stones, mate with them, after which the males allow them to pick up a certain amount of stones.

It is somehow unlikely that the cold of the habitat simplified their existence: among animals, prostitution occurs only in extreme circumstances, when females literally have no other choice. In fact, the Adélie penguins are the only pure example of this kind. A number of researchers are trying to state that prostitution (food) is also in chimpanzees, except for bonobos. But this is not too easy to prove: our closest relative species has complex behavior.Therefore, it is often impossible to reliably understand why the female engages in sexual intercourse outside the "legal" schemes - because of food from the male, because of his social rank, when he is high, or simply at will, if he is low - is often impossible.

Probably, the cold interferes with the Adélie penguins only in the difficult issue of hatching chicks, and otherwise they are completely adapted to the climate and ice? Alas, scientific work shows otherwise: in iceless seasons, Adélie penguins are out of the nest 20-40 percent less time, but at the same time they swim twice the distance - and it is in the water that they get food. In addition, the Antarctic krill, which they feed on, depends on algae for their survival, which grow in large quantities in ice-free seasons - since sea ice blocks a significant part of the sunlight.

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Okay, but these are Adélie penguins - breeding on land, not on ice. Perhaps the emperor penguin, less numerous, but capable of hatching chicks on ice, does not tolerate warming worse?

Frankly speaking, there is no reliable data from our days on this score. Recent liquidations of their colonies due to the migration of large ice masses have proven to be commonplace. It turned out that emperor penguins, getting used to the eternal instability of ice, quickly leave unsuccessful ice platforms and then migrate thousands of kilometers (and this applies even to individuals who are only a few months old). From this, no one can even reliably calculate their number - let alone understand its dynamics and establish whether they are dying out or not.

But if there are no indications from our time, then there is always a history of this species at hand. Genetic data allow us to estimate the number of random mutations that have accumulated in the same emperor penguins throughout their evolutionary history, and thereby understand how long this history has, and even find out how much their number has changed over that time.

Something very strange revealed itself: both the emperor penguins and the Adélie penguins as species are millions of years old (up to ten million). That is, they have experienced warmer periods than they are today. To understand how much warmer it is, suffice it to say that even five million years ago, beech forests were present in Antarctica. True, until the last million years, the number of these two species of penguins was noticeably lower than today. Apparently, the cold waters around Antarctica were not cold enough to feed such large populations. However, there were no noticeable fluctuations in numbers. This means that both species were, albeit not too numerous, but clearly did not die out all these millions of years.

About a million years ago, the temperature "collapsed", on average, to a level noticeably lower than the current one: periodic severe glaciations began. Under such conditions, the number of both penguin species began to gradually increase.

But about 120-130 thousand years ago, a rather strong warming occurred on Earth - so much so that the sea level was six meters higher than the current one, which is why Scandinavia, together with the territory of present-day Finland, was an island. It was so warm that hippos were found in the Thames and the Rhine - and this is not surprising: the average annual temperatures were a couple of degrees higher than the current ones, and in the circumpolar regions they were several degrees higher.

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In such an environment, the Adélie penguins, according to genomic studies, dramatically increased their numbers, but the emperor penguins did not change it in any way. Later, when the warm times ended, the Adélie penguins experienced a sharp, up to 40 percent, decline in numbers, but the imperial ones again kept their numbers unchanged.

It follows from this that emperor penguins, the most seemingly "cold-dependent", in fact show excellent adaptability to various climatic conditions. And in a climate two degrees warmer than today (120 thousand years ago), and in a climate six degrees colder than the present, their numbers did not change noticeably.Millions of years ago it was even warmer than 120 thousand years ago - and still they have not died out. In general, there is no need to worry too much about them: they multiply on the polar night, and ice around Antarctica on the polar night will form for a very, very long time - as they did many millions of years ago.

Polar bear and its seal: victims of warming or their beneficiaries?

The ringed seal is the most abundant large mammal in the Arctic Ocean. Therefore, it is not surprising that the polar bear mainly prefers to eat on it: there are no other equally large (up to 60 kilograms) and numerous candidates for being eaten in local waters. In fact, a bear this size can eat mostly plant foods like its Ice Age cave cousin. By the way, scientists associate its extinction during the peak of the last glaciation precisely with the fact that the too cold climate undermined the food supply, making edible plants for this beast too rare.

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But for a polar bear, this is not yet an option. Yes, he eats berries and other types of plant food when he meets them, but this event in the modern Arctic is still quite rare. So, if there is no ice, the seal will die out, and after it - the largest predator of Russia and the planet itself?

Studying marine mammals by tracking how their numbers change with warming is as difficult as tracking the dynamics of emperor penguins. Unfortunately, no one has carried out a sufficiently thorough analysis of the genome of the seal.

But this does not mean that we cannot figure out how they react to strong and rapid warming. Approximately one to two million years ago, nature set up an experiment on the survival of seals, accustomed to the Arctic climate, in conditions of sharp warming. The ancestors of the Caspian seals at the peak of the next cold snap reached the Caspian Sea, and when the glacier retreated, they did not have time to leave after it.

This is how the Caspian seal, a descendant of the ringed seal, arose. The northernmost and coldest part of its year-round range is Astrakhan, with an average temperature above + 10. The southernmost part of the range is the south of the Caspian Sea, where it is still warmer by several degrees. For comparison: ringed seals in the Arctic Ocean also live where the average temperature is below minus 10.

The obvious conclusion suggests itself: the ringed seal will most likely survive a warming of two dozen degrees. And it will not just survive, but it may well multiply. The fact is that there were more than a million Caspian seals before their mass extermination in the 20th century. The exact number of their Arctic relatives is unknown, but it is estimated to be in the region of two million.

Moreover, the area of ​​the Caspian Sea is less than 0.4 million square kilometers, and the area of ​​the Arctic ringed seal is many millions of square kilometers. It turns out that it is easier for seals to maintain a high "population density" in the water of the warm Caspian Sea than in the cold northern ocean. By the way, the maximum mass of the Caspian seal is higher than that of the Arctic one.

Yes, there is a regular shortage of ice in the Caspian. Some seals breed their cubs (seal pups) in Turkmenistan, where ice is especially difficult. Therefore, they do it directly on sandy beaches (Ogurchinsky Island, the former base of the Caspian pirates, and a number of other places).

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It is clear from this that warming is unlikely to threaten the seals themselves. But what about polar bears? Here again, genome analysis comes to the rescue: polar bears - as a species - are hundreds of thousands of years old (up to 0.6 million). This means that they are guaranteed to survive the warming 120-130 thousand years ago - and there is a high probability that they will survive the current one too. Fortunately, their main food - Arctic seals - clearly does not plan to die out. Another fact indicates the same: the number of polar bears today is at least not decreasing (although the range of many groups is shifting further north).

What Russia will do with the dominance of reindeer

A separate story is reindeer.Indeed, warming makes crust more frequent in the Arctic zone (due to precipitation in the cold half of the year), and it is logical that this should reduce their numbers.

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However, it is not entirely clear whether the deer themselves are familiar with this logic. There are now about a million wild deer in Russia alone. But in fact it is difficult to call it completely “domestic” and those that are considered conditionally domesticated. According to the all-Russian agricultural census of 2016, there were 1.9 million, which is one and a half times more than in 2000. The epicenter of the reindeer population explosion - Yamal - has generally created a situation that until recently seemed inconceivable: the reindeer are literally eating away at the tundra.

This is not an exaggeration. In 1927, there were 20 thousand reindeer on this peninsula, and by last year there were 760 thousand - an increase of 38 times. The “density” of the reindeer here exceeded six individuals per square kilometer, while the plant biomass in the tundra is very low (cold!). Even the reindeer herders themselves understand that the situation is critical: “As the reindeer herder Vitaly Alma says, some areas [of the peninsula] have turned into real sandstone. In some places the animals have eaten the lichen literally to the ground”.

Scientists are also sounding the alarm and suggest taking the reindeer further south to the taiga. Since normally the reindeer herds graze on their own, and the owners do not even know where exactly for most of the year, it will not work voluntarily to “deer” the reindeer. Researchers suggest fencing a piece of taiga or woodland and making animals live there. Local residents are skeptical: "How can a tundra deer be turned into a forest deer, like a reindeer that has always eaten reindeer moss, will begin to eat other types of food?" - asks the hereditary reindeer breeder Nina Jande”.

Although formally these animals are considered "domesticated", it must be understood that in real life, outside the conditions of hunger, they do not eat anything but a reindeer moss, and that, in turn, a person is not able to grow. Therefore, in the very next few years in Yamal, it will be necessary to artificially limit the furious reproduction of reindeer - until they literally ate the local tundra.

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The only thing that inspires hope: among the wild reindeer, in contrast to the "domestic" ones, there are many groups that are still able to exist in the taiga. Perhaps, when their relatives, who are classified as “livestock breeding,” eat up large tundra areas “to the ground”, wild deer will be able to feed in the forests.

And what about the "domestic" animals of this species? There are not so many hopes that along with warming their numbers will somehow subside by itself. The fact is that this species is about a million years old - that is, it is guaranteed to survive the above-mentioned warm period 120-130 thousand years ago, when the Arctic was several degrees warmer than the current one.

Is it all about the pace?

In popular literature, unlike scientific literature, one can often find statements that although warming in itself is really unlikely to kill cold-loving species, its rate may well be. They say, “in the course of evolution, animals have had thousands of years to adapt to gradual changes in conditions; now, due to human fault, the climate changes dramatically in a matter of decades - neither bears nor seals evolve so quickly, they will simply die out."

Alas, this view is based on ignorance of the facts. The end of the ice age is often accompanied by temperature jumps - so sharp that the current anthropogenic global warming, with all its power, has not yet demonstrated such jumps. At the end of the last ice age, the earth warmed so quickly that the sea rose by four to six centimeters a year (16-25 meters in just 400-500 years). Today it rises by three to four millimeters a year. The difference is so great that these values ​​are difficult to compare seriously. At least in the Arctic about 12 thousand years ago, in a matter of decades, the temperature rose by many degrees - more rapidly than during the current global warming. A similar situation was in Antarctica during the same years.

But somehow it didn't work out with the extinction of polar bears and seals. The "lagging behind the train" of the northward glacier on Lake Ladoga formed isolated populations of ringed seals, which as a result live in places where the average annual temperature is 15 degrees higher than that of northern populations of ringed seals. Like the Caspian, these creatures are quite capable of lying on an ordinary shore, and not on an ice floe, and also do not show a tendency towards extinction from warming.

It is extremely doubtful that the current, smoother warming will be able to do what its more abrupt predecessors did not succeed 12-14 thousand years ago.

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