1. The state of the planet Global warming, the protection of biodiversity and the supply of drinking water are the most important problems we have to resolve in order to guarantee the future of Earth. We will be able to achieve these objectives only by developing cleaner sources of energy and changing our ways of living. Global warming is caused by the greenhouse effect: gases from power plants, fumes from cars, agriculture and industry, chlorofluorocarbons trap the heat of the sun and cause this effect. The chlorofluorocarbons also reduce the ozone, a layer of gas that encircles the Earth and protects us from suns harmful UV rays. The glaciers are thawing out, the level of the sea is rising and some parts of Earth are going to be submerged.

2. Biodiversity Another serious problem concerns biodiversity, which is the variety of life on Earth: more than 11.000 species of animals and plants are threatened by extinction, about a third of all coral reefs are expected to vanish with in the next 30 years, and about 15 million hectares of forest are completely destroyed every year.

3. Water The elements essential to life are air and water. The water problem must be resolved: drinking water is essential to life and it isnt unlimited. People who live in developed countries take it for granted, but it isnt true. In developing countries, like Africa and Asia, people lack clean water and they fight to conquer the small amount that is left.

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