Six billion people. That’s the current human population on Earth, and the highest ever reached as well. Things start to get cramped in the cities, while there is everywhere a noticeable depressing atmosphere due to having too many people around, whether that’s in a traffic jam, in shops, at public services etc.

The number of six billion human lives would never have been reached if it wasn’t for fossil fuels. The energy sent by the sun and received by the Earth every day could ever sustain more than two billion people. Fossil fuels combine a sort of energy saved below the surface of the planet, now extracted by humans to use this energy and cover their needs. And with all needs easily covered, humanity was and is able to rise in population.

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Tropical rainforests have the largest biodiversity of all ecosystems on Earth. The soil is rather poor, but it sustains a great variety of plants. It is estimated that 65% of the known plant species are found in rainforests.

During the past three decades, rainforests have been decreasing in size for various reasons, though all of them are connected with human activities. Human populations living near rainforests had the impression that the soil must have been really fertile, as it could sustain such a variety of plants. So, when human started to need more fields for cultivation, they choose rainforests’ earth, and thus they set big fires to get rid of big trees and to obtain space. By the time it was understood that the soil wasn’t suitable for agriculture, many square kilometres of rainforests had already gone.

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