The main cause of the loss of biodiversity can be attributed to the influence of human beings on the world’s ecosystem.

The threats to biodiversity can be summarized in the following main points:

• Alteration and loss of the habitats: the transformation of the natural areas determines not only the loss of the vegetable species, but also a decrease in the animal species associated to them.
• Introduction of exotic species and genetically modified organisms: species originating from a particular area, introduced into new natural environments can lead to different forms of imbalance in the ecological equilibrium. Refer to, “Introduction of exotic species and genetically modified organisms”.
• Pollution: human activity influences the natural environment producing negative, direct or indirect, effects that alter the flow of energy, the chemical and physical constitution of the environment and abundance of the species;
• Climate change: for example, heating of the Earth’s surface affects biodiversity because it endangers all the species that adapted to the cold due to the latitude (the Polar species) or the altitude (mountain species).
• Overexploitation of resources: when the activities connected with capturing and harvesting (hunting, fishing, farming) a renewable natural resource in a particular area is excessively intense, the resource itself may become exhausted, as for example, is the case of sardines, herrings, cod, tuna and many other species that man captures without leaving enough time for the organisms to reproduce.

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http://www.globalissues.org/article/171/loss-of-biodiversity-and-extinctions

http://www.nature.com/nature/journal/v486/n7401/full/nature11148.html

http://www.eniscuola.net/en/argomento/biodiversity1/loss-of-biodiversity/causes-of-the-loss-of-biodi...