Undoubtedly, mankind has become a power that is changing the face of the Earth. Our presence everywhere and obvious influence of human activities on the environment make us think that we are the direct cause of the current succession. As if the nature would remain unchangeable if it were not disturbed. But aren’t we exaggerating our own abilities?
We can only make a final conclusion about our influence after we consider the changes in the context of the whole history of life on Earth.
When we talk about the global warming, we should not forget that we live in the middle of a big glacial period. This means that the planet is much colder than it used to be before. The average temperature in the Mezozoic Era and at the beginning of Cenozoic was about 24*C, while the modern average temperature is only 14*C. Within such temperature scale the changes of the last few thousand years are no more than local fluctuations within the“endless winter”.
Although what is “local fluctuations” in a larger scale of geological time, can be detrimental for individual short-lived organisms and even ecosystems. Dramatic changes in the climate began 30 million years ago, in the middle Cenozoic. They had profound effects on life.
Before the beginning of the glacial period, the planet was covered with forests, warm and wet all around the world. Subsequent cooling, associated with aridisation, progressively formed modern distinct climate zones. Forests began to decline, giving place to vast plains, which eventually transformed into deserts. The last three million years are characterized by rapid cycles of glaciation and warming, resulting in lasting alteration of biomes.
Huge ecosystems, such as so called “mammoth steppe” (or tundra-steppe) developed and disappeared just in a few hundred thousand years, with all its inhabitants. From this point of view, Homo sapience is a kind of a “disaster taxon”, fitted for unstable environment and climatic “surprises”, but not a disaster in itself.
But in this case question arises. What will happen to us in the future? If we are the children of the glacial era, will the end of glacial period be also the end of humanity? We can look for answers in the past.
The current glacial era is not the first one in the history of Earth. The previous event occurred in the Paleozoic era and resuled in the Permian-Triassic extinction event 250 million years ago, known as the most prominent biospheric catastrophe in history.
Within the Permian period, the climate underwent a transition similar to the Cenozoic, from warm and wet to cool and dry. The Coal Forest, previously covering the whole planet, decayed and gave place to vast deserts of the Triassic period. Late Permian was characterized by rapid change of faunas, finally stopped at Permian-Triassic boundary, at the lowest level of biodiversity. Among the survivors there was a new form of life – top predator, quick, clever and hardy, who dominated on land for the next 200 millions years: archosaurs.
What does it have to do with us? Probably we are not only a “disaster taxon”. We are a new form of life, which will give rise for the new diversity in the oncoming era, more organized then it was before.
На самом деле, я тут специально много "дырок" сделала, чтоб публика могла прикапываться и задавать вопросы. А еще к этому положено много красочных картинок и графиков.