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Water is vital for the existence of all life. We live in a world that has it in abundance, yet most of this water is inaccessible to us. Ninety-seven per cent is sea water, too salty for terrestrial life to use. Just three per cent exists as freshwater, and almost all of this is locked up as ice or hidden underground. Only a tiny fraction can be accessed by life on land 鈥� and only then through the action of our planet鈥檚 weather. For weather is the force that distributes this freshwater around the world.

Every year, the sun evaporates 434 million billion liters of water from our oceans 鈥� 20 times the volume of all the Great Lakes of North America and Canada combined. This water rises into the sky, where it forms clouds, before falling as rain, sometimes thousands of miles away. Without the sun making rain, there would be no freshwater on Earth 鈥� and terrestrial life could not exist.

But where water is concerned, our planet is not created equal. Some regions experience extreme amounts of rain year round, some just a few millimeters, whilst others must deal with extreme shifts between wet and dry seasons. This distribution of freshwater around the globe has shaped the lives of animals all across the planet 鈥� and in doing so, it has given rise to an incredible diversity of species and habitats, from the driest desert to the lushest tropical rainforest.