Virtual Museum of Canada
Jardin botanique de Montral 
Centre for Forest Research

Water and the biomes

Water impact on biodiversity

The Earth's major biomes are determined by temperature and, in particular, by the availability of water. In general, when there is lots of water, there is lush plant life. When water is scarce, on the other hand, trees are much less numerous and varied. Their distribution depends on the availability of water. Think about it: in a temperate northern zone, a mature tree can lose 500 litres of water in a single day through transpiration. So in one square kilometre of forest, that adds up to about 500,000 cubic metres of water per year, or more than three Olympic pools a year that vanish into thin air! It's clear that it takes water to make a forest.

Where's there's water...

Trees' reliance on water can also be seen on a local scale. Imagine the following scenario: You're strolling through a pretty maple stand one springtime Sunday, walking off the big meal you've just had at a sugar shack. You climb a hill and find some lovely oak trees. Farther on, down a gentle slope, you ford a stream and come across some black ash. You're still on the sugar shack property, and yet you're running into all kinds of different trees. Here too, the tree population depends on the availability of water.

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