Excepting the Patagonian Andes, the rest of the region is quite arid, even the Atlantic coast. This is due to the Andes themselves. The predominant winds come directly from the west, from the Pacific Ocean, but the Andes make the winds ascend, making them go to the colder air above, thus making moisture condensing and falling in the form of rain and snow. In that way those big and fluffy clouds coming from the Pacific unleash all their rain power over Chile and part of the Argentinean Andes and come out dry to the eastern side of the mountain ridge. The impact of this is quite dramatic and if one drives in an east - west line the you will not only witness the change between Mountains to flatlands but you will see trees disappear and give way to "Coirones", "Neneos", rocks and basically no green to be seen. In that way you can go from the Valdivian rainforest (the coldest rainforest in the world) to the semi-desert Patagonic Plateau in less than 100 Km, from precipitations of about 9000 mm/year to less than 100 mm/year.

Another "strange" thing is seeing enormous lakes and wide rivers going through an almost desert without altering the Vegetation either in colour or type.

Most of living beings on this little blue marble we call earth depend on water to survive, so water (or lack of it, in this case) has a great impact on al living things and it affects geography in a way that no other element (with the possible exception of the hand of man) does. A small change in the precipitation amount a place have can have a huge impact over the way it looks, now just imagine the enormous impact the dramatic precipitation change has over the biodiversity of Patagonia.