This paper takes part in the series essay competition of “great science” of Recordunkown.
The earth is a beautiful life world. Since the birth of the early primitive life 3.8 billion years ago, through continuous evolution, the life world with rich species has been formed. At the same time, the intelligent life human has also been born.
So is the long evolutionary road of life smooth? Of course not. In fact, there have been five mass extinctions in the earth’s life span of nearly 500 million years, and it is believed that there were also mass extinctions 500 million years ago. It’s just that it’s too old to be discovered by geological structure.
According to the geological structure, the first mass extinction occurred at the end of the Ordovician period 440 million years ago, also known as the Ordovician mass extinction. This disaster caused about 85% of the species extinction. And the last mass extinction is what we all know, the dinosaur mass extinction happened 65 million years ago, which made more than 80% of the earth’s life disappear.
The cause of mass extinction is closely related to the dramatic changes of the earth’s ecology. The previous four mass extinctions were all caused by dramatic changes in the earth’s ecology, and most of the organisms could not adapt to the changes of the environment, so they became extinct. Although the fifth mass extinction was caused by the impact of an asteroid, the impact of an asteroid eventually caused the dramatic changes of the earth’s ecology.
Through the statistical study of the five mass extinctions in the past 500 million years, scientists found that the occurrence of mass extinctions is very regular. As long as it takes a long time, new mass extinctions will occur. If so, 65 million years have passed since the fifth mass extinction. In terms of time cycle, it seems that it is time for the sixth mass extinction.
Therefore, scientists have been actively studying and exploring the changes of the earth’s ecology, trying to figure out what is the current situation of the earth’s ecology? Has the sixth mass extinction started? In order to predict the occurrence of mass extinction in advance, we need to study some characteristics of environmental upheaval in the last mass extinction.
How to observe these characteristics? Scientists have come up with a very special kind of marine coral. Coral is a very common creature on the sea floor. Many people regard coral as a plant. In fact, it is an animal belonging to Coelenterata, with more than 7000 species.
Coral image like branches, colorful and beautiful, many people use them to do decorations. So what does coral have to do with mass extinction? In fact, many people do not know that coral is a very sensitive marine life to the environment. If the marine environment changes and other organisms, including humans, are unable to sense the change, corals will show some warning features first.
Therefore, scientists pay great attention to the changes of corals when they study the ecological changes of the earth, because the information about corals is very useful. 65 million years ago, an asteroid hit the earth, causing global earthquakes, tsunamis, volcanoes and large-scale wildfires.
During the period of time when the asteroid hit the earth, the temperature of the earth first entered the ice age, and then rose rapidly. The reason is the eruption of global volcanoes, a large number of magma and volcanic ash, blocking the sun. At this time, the temperature of the earth began to decline. With the global cooling, some greenhouse gases such as carbon dioxide were constantly trapped in glaciers and permafrost.
After the reduction of greenhouse gases in the atmosphere, the earth will further cool down, which will lead to the further sequestration of greenhouse gases. As the earth entered the ice age, and the sun was covered by volcanic ash, plants could not enter photosynthesis, so a large number of plants began to die, and a large number of animals could not adapt to the environment and continue to die out.
In fact, the reason for the extinction of dinosaurs is that they were starved to death. We should know that dinosaurs are huge and need a lot of food every day. But a large number of plants died, herbivorous dinosaurs without food continue to extinction, carnivorous dinosaurs because there is no food and continue to starve to extinction.
Later, as the dust particles in the atmosphere gradually fall to the earth, the sunlight can re-enter the earth, leading to the melting of glaciers and permafrost in some areas. The frozen greenhouse gases are re emitted into the atmosphere, which further leads to the warming of the earth. In the whole process of environmental upheaval, volcanic ash, dust and gas produced by asteroid impact also cause various sulfides to enter the atmosphere, leading to acid rain and ocean acidification.
71% of the earth’s surface is the ocean. The impact of asteroids on the earth has brought about ecological upheaval, and the ocean is also inevitable. Corals, which are ubiquitous in the ocean, are very sensitive organisms, so these ecological changes will show some characteristics on corals, such as: living in deep water area more than 100 meters below; worldwide distribution; not symbiotic with other organisms; living alone; bleaching resistance, etc.
The performance characteristics of these corals are actually adjustments made by corals in order to adapt to new environmental changes. If the corals in the ocean also have these characteristics, does it mean that a new mass extinction is about to begin? The answer is obvious. By studying the corals in the seabed, scientists found that the situation of corals today is very similar to 66 million years ago, which means that the earth may be experiencing the sixth mass extinction.
If the earth has really entered a new round of mass extinctions, then the cause of all this may be very different from the previous five mass extinctions. The first five were natural environmental changes or extraterrestrial disasters, while the sixth mass extinction was caused by human industrial activities.
As we all know, since mankind entered the industrial age, it has been continuously releasing carbon dioxide and other greenhouse gases into the atmosphere. With the increasing of greenhouse gas content, the greenhouse effect is aggravating and the temperature of the earth is rising. In recent years, the rising trend of the earth’s temperature is very obvious. When the earth’s temperature rises to a certain extent, it will make the earth’s ecology collapse completely and cause a huge ecological disaster.
Corals are particularly sensitive to the environment. Affected by human disturbance, global warming and ocean acidification, more than 30% – 50% of coral species will be extinct in the next few decades or several worlds. The extinction of corals is like a wake-up call to mankind, reminding us that in addition to corals, other creatures on earth will also face the test of survival, including primates.
According to scientists’ estimation, if human beings do not protect the existing environment, 75% of the creatures will face extinction in the next few centuries or even thousands of years. The speed of this kind of extinction is more than 100 times of the normal rate of extinction. Therefore, scientists believe that the earth may be experiencing the sixth mass extinction.
Of course, many people will say, why can’t I feel the sixth mass extinction? In fact, except for the fifth mass extinction, which came suddenly and violently due to the impact of asteroids, the other four mass extinctions lasted for a very long time, basically more than millions of years. The whole process of mass extinction is slow and mild, and the most obvious feature of mass extinction is that the environment is getting worse and worse, and the organisms are constantly disappearing.
Compared with our current earth ecology, the environment is getting worse and worse, and every year there will be extinction. In fact, this is very consistent with the characteristics of mass extinction. Therefore, it is very reasonable for scientists to say that the earth may have entered the sixth mass extinction, but the process may be relatively long.
In the early stage of the mass extinction, we may just feel that the environment is getting worse and worse, and the impact on human beings will not be great. But if the mass extinction develops to the middle and late stage, the situation will be completely different. At that time, ecological collapse is the real end. Of course, at that time, mankind might have been an interstellar civilization and had the ability to colonize the outer planet. If the earth could not survive, we could also survive on other planets, and human civilization could continue.
Guys, what do you think of this? Welcome to leave a message below to discuss and express your opinions.