Biologically speaking, humans are far from the most successful species. Our planet has known animals that have existed for millions of years, but still extinct. Will humanity not follow them?
THE EARTH IS A HARD HOST
Our planet seems to us as a world ideally suited for human life. Favorable temperature conditions, oxygen atmosphere, sufficient water and food.
However, today scientists, delving into the prehistoric past of our planet, come to the conclusion that it is far from being as benevolent to the creatures living on it as it seems. Many times life on Earth found itself on the verge of complete extinction, as evidenced by the remains of a myriad of biological species that have forever sunk into the past. Now it is becoming more and more obvious that life exists in spite of external conditions rather than due to them.
It is as if an endless war is going on on our planet between the kingdom of animate and inanimate nature. Living conditions for four and a half billion years of its existence have changed dramatically many times. When life first began in the ancient oceans, the conditions on Earth were such that almost none of the living creatures would last a minute on it.
According to the theory of "Snowball Earth", which finds a lot of factual evidence, in the period from 850 to 630 million years ago, our planet was completely covered with an ice shell. While in the Mesozoic (252-66 million years ago) the average annual temperature was 25-30 degrees Celsius - for comparison, in our time this figure is 14 degrees.
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Today paleontologists are aware of at least five mass extinctions of living things. The largest of them happened in the Permian period, 251 million years ago, when more than ninety percent of living beings disappeared from the face of the Earth. The reason for this was the eruption of a supervolcano on the site of present-day Siberia, which lasted, apparently, hundreds of thousands of years and poured out two billion cubic meters of molten rock onto the surface.
Extinction is coming
The five great extinctions are not all that the planet's biosphere had to face. There are a great many other cases of reduction in species diversity, not so large-scale, but no less tragic from this.
The last of them happened already during the period when our ancient ancestors roamed the Earth - we are talking about the disappearance of representatives of the Pleistocene megafauna, such as mammoths, cave bears, saber-toothed cats, giant sloths and others. Since this happened not so long ago, then who can guarantee that this will not happen again, and a person will not become a victim of a new catastrophe?
Today, scientists almost unanimously argue that there are a number of serious risks to humanity. So, it is quite possible that we will repeat the fate of the dinosaurs that dominated our planet for 160 million years and died after a ten-kilometer asteroid fell on the Yucatan Peninsula.
Currently, scientists have developed the so-called Turin scale, which estimates the probability of collision of our planet with celestial objects. It identifies five main risk zones: from a white zone (0 on a scale), which means there is no risk of collision, to a red (8-10 on a scale), when a collision is inevitable and threatens a disaster of varying severity.
In 2004, the asteroid Apophis was discovered, the hazard of which is estimated at four points on the Turin scale (yellow zone requiring constant monitoring). In 2029, it will pass 37.5 thousand kilometers from the Earth - geostationary satellites rotate at this distance. Once in this zone, the asteroid will fall under the strong influence of the gravitational field of our planet, as a result of which, at the next approach in 2036, it may collide with it. In this case, the force of the explosion will be from 506 to 1480 megatons in TNT equivalent.
For comparison, the power of the bomb dropped on Hiroshima was 18 kilotons. We are lucky if Apophis falls on land - he "just" erase everything within a radius of fifty kilometers into dust and cause an earthquake of 4-6 points on the Richter scale. But if the impact hits the water surface, which is much more likely, the raised tsunami will sweep away all settlements at a distance of 300 kilometers from the coast, and the evaporated water, once in the atmosphere and forming clouds, will be able to lead to climate change.
Apophis is the closest threat from space, but not the worst. For example, the half-kilometer asteroid Bennu discovered in 2013 may collide with Earth in 2169 or 2199, and the consequences of this impact will be at least twice as severe as in the case of the fall of Apophis.
Already, 6500 asteroids are known to pose a potential threat to the planet, and their number is constantly growing. Unfortunately, telescopes are not able to cover the entire sky with their gaze, so no one excludes that a huge celestial body is already moving towards us, which has not yet been discovered by scientists.
PANDEMIC
Another threat that may turn out to be even more real than an asteroid fall is a pandemic: an epidemic of a deadly disease that spreads across the globe. There are theories according to which in the past some extinctions of biological species were triggered by the spread of diseases among them.
A similar phenomenon is observed in our time: from 1980 to 2004, 120 species of frogs disappeared, many are under threat of extinction. The main reasons for this are infectious diseases with chytromedicosis, ranavirus and the spread of the parasitic worm ribeiroi.
Humanity has already faced deadly epidemics in the past. For example, in the Middle Ages, the plague wiped out 30-50 percent of the population in Europe. At the same time, "black death" is far from the most dangerous disease that exists on the planet. Before the era of antibiotics, mortality was 95% in bubonic plague and 99% in pneumonic, but the spread of the epidemic was quite successfully contained by quarantine and sanitary measures.
Modern methods of treatment using streptomycin and other antibiotics of the aminoglycoside group can save the lives of nineteen out of twenty patients. But the Ebola hemorrhagic fever, which is raging in Africa and has already claimed thousands of lives, despite all the advances in medicine, has a mortality rate of up to ninety percent.
So far, its spread is difficult, but constrained within West Africa, but the forecast is disappointing. It’s hard to imagine what would happen if the Ebola virus broke through all the quarantine cordons.
It is completely unclear how to combat the human immunodeficiency virus that causes AIDS, the plague of the twenty-first century. First identified in the 1980s, it has already infected 35 million people. And although death occurs 9-11 years after infection, it is usually inevitable, and during this time the patient will have time to infect several more people. The dynamics of the spread of HIV infection does not cause optimism, and it is possible that sooner or later it will strike the whole of humanity and cause its gradual extinction.
Many scientists argue that the discovery of diseases unprecedented in their danger lies ahead of us. According to experts, many deadly viruses capable of destroying humanity are still lurking in hard-to-reach regions of Africa and Asia.
The fact that they have not yet shown themselves is due to their locality: after infecting a resident of some remote village, such a virus manages to destroy all his fellow villagers before they spread the disease to neighbors living tens and hundreds of kilometers away. However, as civilization comes to such uninhabited regions with its roads and big cities, the risk of releasing the disease rises.
By the way, this is exactly what happened with Ebola: known for a long time, it destroyed individual African villages, but did not pose a danger to a large number of people until modern vehicles became assistants in the spread of this disease.
We must not forget about the risk that artificial viruses, created as biological weapons, can escape from laboratories. What will be the consequences of such disasters, it is better not to think.
SUPERVOLCANO
No matter how terrible asteroids and diseases are, a person has a chance to cope with them. Already, projects are being considered to deviate from the Earth the most dangerous celestial bodies, and new drugs are invented against viruses. But what people are really helpless against is in front of the forces lurking in the depths of our planet.
One of the likely killers of humanity is the Yellowstone supervolcano located in the United States. There is a nature reserve of the same name, known for its geysers and hot springs, but the volcano itself is so huge that people understood what they were dealing with only in the 1960s, when a cyclopean crater 55 by 72 kilometers in size was seen in images from space.
At the same time, a magma bubble remains under the crater, fed by a giant plume - a vertical flow of mantle rock, heated to 1600 degrees Celsius. As scientists have established, over the past seventeen million years, there have been about 142 eruptions, the last of which happened 640,000 years ago. Each of them was so powerful that it destroyed nearby mountain ranges, and the masses of volcanic ash thrown into the atmosphere, reflecting the sun's rays, created an effect reminiscent of a "nuclear winter".
Large prismatic source. Yellowstone National Park, USA
According to the calculations of a number of volcanologists, the next period of calm of the Yellowstone supervolcano is now coming to an end, which means that the risk of its eruption is growing every year. It is impossible to predict the exact time of the beginning of the catastrophe: maybe it will happen in a thousand years, or perhaps next week. One way or another, the consequences will be fatal for human civilization.
These are just some of the possible scenarios. The blow can come from the side, the existence of which we do not even suspect. In any case, it is worth remembering that humanity still remains extremely vulnerable to natural disasters.
Therefore, people should use as productively as possible every year that the world around them has graciously allocated for our existence.