Lichen can grow successfully in a remarkable variety of different habitats. They are very drought tolerant and can quickly absorb many times their weight in water. They have the ability to absorb water from fog and dew and even from the air itself where the humidity is high. They also dry out very slowly, which allows the algal and cyanobacterial partners to photosynthesize for long periods of time. All of these attributes allow for lichen to grow in the harshest of Earth's environments, such as deserts and the cold polar regions.
Green is good
The green algal and the cyanobacterial partners of lichen possess the green pigment chlorophyll and carry on the life-sustaining process of photosynthesis. They also provide vitamins to their fungal partners. Cyanobacteria have the ability to make nitrogen directly from the surrounding air, something neither the algae nor fungi are capable of doing.