The team of researchers believes that the end of civilization will come within decades. In the new study, which was published in Nature, the researchers wrote, "Clearly it is unrealistic to imagine that the human society would start to be affected by the deforestation only when the last tree would be cut down." Before humans started to dominate the world, the planet was covered by 60 million square kilometers of the forest but now there are less than 40 million square kilometers of forest, revealed the study. As trees and forests play a huge role to balance Earth's ecosystem, fewer forests will cause more deduction of oxygen from the blue planet and create an unwanted change in the food chain. "It is highly unlikely to imagine the survival of many species, including ours, on Earth without [forests]," the study added.