Human civilization is developing very rapidly. Only five thousand years ago the first nodular writing system appeared - and today we have already learned how to exchange terabytes of information at the speed of light. And the pace of progress is growing.
It is almost impossible to predict what the human impact on our planet will look like in at least a thousand years. However, scientists love to fantasize about what awaits the Earth in the future if our civilization suddenly disappears. Let us follow them and imagine an unusual situation: for example, in the XXII century all earthlings will fly to Alpha Centauri - what then awaits our abandoned world?
Global extinction
Through its activities, humanity constantly influences the natural cycle of substances. In fact, we have become another element capable of causing a cataclysm of unprecedented proportions. We are changing the biosphere and climate, extracting minerals and producing mountains of garbage. But, despite our power, it will take nature only a few thousand years to return to its former “wild” state. Skyscrapers will collapse, tunnels will collapse, communications will rust, the territory of cities will be conquered by a dense forest.
Since emissions of carbon dioxide into the atmosphere will stop, then nothing can prevent the onset of a new ice age - this will happen in about 25 thousand years. The glacier will begin to advance from the north, pinning down Europe, Siberia and part of the North American continent.
It is clear that under many kilometers of creeping ice the last evidence of the existence of civilization will be buried and ground into fine dust. However, the biosphere will suffer the most. Having mastered the planet, mankind practically destroyed natural ecological niches, which led to one of the most massive animal extinctions in history.
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The departure of humanity will not stop this process, because the chains of interaction between organisms have already been disrupted. Extinction will continue for over 5 million years. Large mammals and many bird species will disappear completely. The biological diversity of the fauna will decrease. An obvious evolutionary advantage will be gained by genetically modified plants, which scientists have adapted to the harshest living conditions.
Such plants run wild, but being protected from pests, they will quickly take over the vacated niches, giving rise to new species. Moreover, during these millions of years, two dwarf stars will pass at a close distance from the Sun, which will inevitably lead to a change in the planetary characteristics of the Earth, and a hail of comets will fall on the planet. Such catastrophic phenomena will further accelerate the plague among the known species of animals and plants. Who will replace them?
Revival of Pangea
It has long been established that the earth's continents move, albeit very slowly: at a speed of several centimeters per year. During human life, this drift is practically invisible, but over millions of years it can radically change the geography of the Earth.
In the Paleozoic era, there was a single continent Pangea on the planet, washed from all sides by the waves of the World Ocean (scientists gave the ocean a separate name - Panthalassa). About 200 million years ago, the supercontinent split into two, which in turn also continued to split. Now the planet is waiting for the opposite process - the next reunification of land into a common colossal territory, which scientists have dubbed Neopangea (or Pangea Ultima).
It will look something like this: in 30 million years Africa will be closed in Eurasia; in 60 million years, Australia will crash into East Asia; in 150 million years Antarctica will join the Eurasian-African-Australian supercontinent; in 250 million years, both Americas will be added to them - the process of the formation of Neopangea will be completed.
Continental drift and collisions will significantly affect the climate. New mountain ranges will appear, changing the movement of air currents. Due to the fact that ice will cover most of Neopanga, the level of the World Ocean will drop markedly. The global temperature of the planet will fall, but the amount of oxygen in the atmosphere will increase. In areas of a tropical climate (and such, despite the cold snap, will always be), an explosive increase in species will begin.
Insects (cockroaches, scorpions, dragonflies, centipedes) develop best in such an environment, and again, as during the Carboniferous period, they will become real "kings" of nature. At the same time, the central regions of Neopanga will be an endless scorched desert, since rain clouds simply cannot reach them. The temperature difference between the central and coastal regions of the supercontinent will cause monstrous monsoons and hurricanes.
However, Neopangea will not last long by historical standards - about 50 million years. Due to the powerful volcanic activity, colossal cracks will cut through the supercontinent, and parts of Neopanga will be divided, starting to "free float". The planet will again enter a warming period, and the oxygen level will fall, threatening the biosphere with another mass extinction. A certain chance of survival will remain for those creatures that adapt to life on the border of land and ocean - primarily amphibians.
New person
In the press and science fiction, one can find speculative statements that man continues to evolve, and in a few million years our descendants will be as different from us as we are from monkeys. In fact, human evolution stopped at the moment when we found ourselves outside natural selection, gaining independence from changes in the external environment and defeating most diseases.
Modern medicine allows even such children to be born and grow up who would have been doomed to die in the womb. In order for a person to begin to evolve again, he must lose his mind and return to an animal state (before the invention of fire and stone tools), and this is practically impossible due to the high development of our brain. Therefore, if someday a new man appears on Earth, he is unlikely to come from our evolutionary branch.
For example, our descendants can enter into symbiosis with a closely related species: when a weaker, but intelligent monkey controls a more massive and formidable creature, literally living on the back of the neck. Another exotic option is that a person will move to the ocean, becoming another marine mammal, but due to climate change and a shortage of resources, he will return to land in the form of a hulking “aquabiote” crawling in search of food. Or the development of telepathic abilities will direct the evolution of new people in an unexpected direction: communities of "hives" will arise, in which individuals will be specialized, like bees or ants …
In 250 million years the galactic year will end, that is, the solar system will make a complete revolution around the center of the galaxy. By that time, the Earth will be completely transformed, and any of us, if he gets into such a distant future, is unlikely to recognize a home planet in it. The only thing that will remain at that time from our entire civilization is small footprints on the moon left by American astronauts.
Paleontologists have established that mass extinctions of animals were a periodic phenomenon in the past of the Earth. There are five mass extinctions: Ordovician-Silurian, Devonian, Permian, Triassic, and Cretaceous-Paleogene. The most terrible was the "great" Permian extinction 252 million years ago, as a result of which 96% of all marine species and 70% of terrestrial animal species died. Moreover, it also affected insects, which usually manage to avoid the devastating consequences of a biosphere catastrophe.
Scientists have not been able to determine the causes of the global pestilence. The most popular hypothesis is that a sharp increase in volcanic activity led to the Permian extinction, which changed not only the climate, but also the chemical composition of the atmosphere.
Anton Pervushin