Tundras and ecological concerns?

ok I have a science project due on monday ok what are two ecological concerns of the tundra and what effect does it have on the tundra and how did it come upon the tundra
second of all what are two symbiotic relationships between animals in the tundra just between two animals not between 2 plants please Help!

Major concerns are the fate of permafrost and the carbon contained in Arctic peat. Decomposition of this carbon could increase the concentration of carbon dioxide in the atmosphere.

source: http://www.biologyre...

Symbiosis, the only thing I can find is lichen and fungus, but they are plants.