Human civilization is developing very fast. Only five thousand years ago first nodular writing was introduced, and today we have learnt to share terabytes of information at light speed. And the pace of progress is increasing.
Predicting what human impact on our planet may be even a thousand years into the future is almost impossible. However, scientists love to speculate as to what awaits the earth in the future if our civilization suddenly disappears. Let us follow them and envision an unusual situation, for example, what if in XXII century all humans will leave Earth for Alpha Centauri, what is going to happen to our forsaken world?
Because of its development, mankind constantly affects the natural process of matter cycling. In fact, we have become a kind of disaster that can cause a cataclysm of unprecedented proportions. We are changing biosphere and climate, extracting minerals and producing mountains of garbage. But, despite our power, the nature may require only a few thousand years to return to its original “wild” state. Skyscrapers will crumble, the tunnels will collapse, communication lines will rust out, and urban areas will be replaced by a dense forest.
Since the emissions of carbon dioxide in the atmosphere will end, nothing can prevent an onset of a new ice age, it may happen in about 25 thousand years. The glaciers will begin to advance from the north, taking over Europe, Siberia and parts of the North American continents.
It is obvious that under kilometers of encroaching ice layers, the last traces of once-existed civilization will be buried and ground to a fine dust. Still, the greatest impact will be suffered by the biosphere. Having completely taken over the planet, mankind has virtually destroyed every natural ecological niche, which led to one of the greatest mass extinctions of animals in history.
Absence of humanity will not stop this process, because the chains of interactions between living organisms are already negatively impacted. Mass extinction will continue taking place for over 5 million years. Large mammals and many species of birds will be wiped out. The biological diversity of fauna will drastically decline. The obvious evolutionary advantage will be gained by genetically modified plants, which scientists have designed to be able to withstand the most challenging conditions for their survival.
These plants will start growing in the wild, and while being resistant to pests, will quickly take over vacated niches, creating new species. Moreover, during those millions of years, two dwarf stars will appear in the close proximity to the Sun, which will inevitably lead to changes in planetary characteristics of the Earth, which will also experience bombardment of comets. These catastrophic events will further accelerate extinction among the known species of animals and plants. What are they going to be replaced with?
The revival of Pangea
It has long been established that continents on Earth are moving, albeit very slowly, at a rate of several centimeters per year. In the course of a human life, this drift is almost imperceptible, but over millions of years, it can radically change the geography of the Earth.
In the Paleozoic era there was a single continent called Pangaea, surrounded by the waters of the World’s ocean (scientists have given it a name – Panthalassa). About 200 million years ago this supercontinent has split into two parts, which in turn, also continued to disintegrate. Now the planet is about to experience a reverse process, the reassembly of land mass back into an enormous continent, which scientists have dubbed Neo-Pangaea (or Pangaea-Ultima).
This process will look something like this: in 30 million years Africa will be joined with Eurasia, in 60 million years Australia will collide with Asia, in 150 million years the Eurasia-Africa-Australia supercontinent will be joined by Antarctica, and in 250 million years, both American continents will be added and the process of forming Neo-Pangaea will be completed.
Drifting and colliding of continents will significantly impact the climate. New mountain ranges will appear, changing the distribution of air masses. Due to the fact that the ice will cover most of the Neo-Pangaea, sea levels will drop significantly. The global temperature of the planet will fall, but the amount of oxygen in the atmosphere will increase. In areas of tropical climate (which will still be present despite global cooling) an explosive start to formation of new species will take place.
Insects species which are most adapted to this kind of environment (cockroaches, scorpions, dragonflies, millipedes), will once again rule the world, just like at the time of the Carboniferous period. At the same time, the central regions of Neo-Pangaea will be a scorched desert expanse, because rain clouds will not be able to reach these areas. The difference in temperatures between the central and coastal areas of this supercontinent will cause horrendous hurricanes and monsoons.
However, Neo-Pangaea will not exist for long by historical standards, only for about 50 million years. Due to the powerful volcanic activity, the supercontinent will be transected by huge cracks and parts of Neo-Pangaea will split apart, and start “floating freely”. The planet once again will enter a period of warming, and oxygen levels will fall, threatening the biosphere with another mass extinction. The only chance of survival will remain for those creatures which will be able to adapt to life on the border of land and ocean, namely amphibians.
The new human
Print media and science fiction sources assert that humans continue to evolve, and in a few million years our descendants will be as different from us as we are different from apes. In fact, the evolution of man stopped at the time when we diverted from natural selection and gained independence from changes in the environment by defeating the majority of diseases.
Advances in medical science allowed even those children who have been condemned to death in the womb to be born and survive. For humans to go back to evolutionary changes, they would need to lose their highly-developed brain and go back to the animal state (to the period before discovering fire and inventing stone tools), but it is impossible due to our superior development of the brain. Therefore, if one day the world will have a new human species appearing, then it is unlikely to happen based on our evolutionary branch.
For example, our descendants may enter into a symbiosis with a closely related species, when a small but clever ape-like creature directs a more massive and formidable creature, literally living on the back of its neck. Another exotic option is when people will move into the ocean, becoming another marine mammal, but because of climate change and resource scarcity will return to the land in the form of clumsy “aqua biota” searching the land for food. Or the development of telepathic abilities will direct the evolution of new human race into an unexpected direction: hive-like communities in which the species will be specialized, similar to bees or ants.
After 250 million years the galactic year will come to an end, that is, the solar system will make a full rotation around the center of the galaxy. By this time, the Earth will be completely transformed, and any one of us, being present in such a distant future, would hardly recognize our home planet. The only thing that will be left remaining of our entire civilization are small footprints on the moon by U.S. astronauts imprinted on the surface.
Paleontologists have found that mass extinctions have been a periodic phenomenon in the Earth’s past. There are five mass extinctions: Ordovician-Silurian, Devonian, Permian, Triassic and Cretaceous-Paleogene. The most devastating was the “great” Permian extinction 252 million years ago, which wiped out 96% of all marine species and 70% of terrestrial species. Moreover, it has also affected insects species, which can usually survive devastating impacts of biospheric catastrophe.
Scientists have been unable to determine the cause of global die-out. The most popular hypothesis states that the Permian extinction has led to a sharp increase in volcanic activity, which changed not only the climate, but also the chemical composition of the atmosphere.