Notes

The ecosystems most threatened All environments are not exposed to the same dangers: some have been profoundly upset by humans, even destroyed, while others suffer only marginal disturbances. Danger in the home No natural environment is entirely immune to human action. Certain ecosystems are particularly threatened because they are highly coveted or because their capacity to regenerate is weak. Significant biodiversity does not necessarily confer economic interest on the environment, but unfortunately it is often the richest environments that suffer the greatest damage. This is the case with tropical forests: exploited for the export of precious woods and cleared by My peasants, they fail to reconstitute spontaneously once destroyed.
Corals and freshwater life in danger Coral reefs are victims of looting (fishing with dynamite and cyanide, in particular) and struck by destructive diseases, probably linked in part to pollutant discharges (coral only tolerates crystal clear waters) and global warming of the oceans. The best known is bleaching For fifteen years, this phenomenon has been increasing on reefs around the world, those of the Caribbean are already affected at 60% l Similarly, life in freshwater suffers from human behavior. Various more or less toxic wastes are simply dumped into the currents, the runoff of the rains carries in the rivers the residual substances of modern agriculture (pesticides, fertilizers, livestock effluents). However, the dilution capacity of rivers and streams is very limited.
Wetland ecosystems are also vulnerable to the boundary between the terrestrial and aquatic environment (peat bogs, swamps, mangroves. They are often considered sterile and unhealthy, while they host many species and play an essential ecological role in the regulation of the flows. One tends to convert them into "productive zones": drained or filled, they form agricultural or industrial plots. The recent floods in Europe are perhaps not foreign to these practices The polar zones are not spared The specific biodiversity is certainly particularly low there, nevertheless, in these regions there are large mammals (polar bears, seals, walruses and various cetaceans), aquatic invertebrates, many birds and fish, however industrial fishing and pollution atmospheric generated by industrial activity (dioxins. mercury ...) which manages to gain these territories creates And the global warming is already having serious consequences: the populations of emperor penguins in Antarctica have decreased by more than 50% during the last twenty-five years following the warming of the Southern Ocean. .
I Polar bears, like all large carnivores located at the top of the food pyramid, concentrate in their bodies many pollutants resulting from human activities (dioxins, mercury, pesticides ...). Forests and plantations There are over a million square kilometers of forest plantations on the planet, which are generally alignments of trees of the same variety, fast growing (mainly eucalyptus and pines, poplars, etc.). Admittedly, these plantations fulfill ecological tasks (water regulation, soil fixation, carbon storage, etc.), supply wood for industry and relieve old-growth forests of some of the economic pressure that s 'exercises on them. But their biodiversity is much lower than that of the forests they replace.
A Read the text and answer the questions: 1 What does “petil in the home” mean Inaction can become a source of danger b Inaction is not a source of danger S Ecosystems are threatened within people 2 Explain INec in your own words what is going on in the trepical areas 3 What are the four threats to coral reefs? 4 Why is the text illustrated with a photo of a mangrovel What is the threat this poses to this environment? 5 How is human action detecting the diversity of the polar zones. 6 Explain in your own words what is going on with polar bears. 7 What is the disadvantage of planting trees