"The climatic changes in progress in the Sierra, bearing upon the tenure of forest life, are wholly misapprehended, especially as to the time and means employed by nature in effecting them. It is constantly asserted, in a vague way, that the Sierra climate was vastly wetter than now, and that the increasing drought will of itself extinguish sequoia in a short time, leaving the ground to firs and pines supposed to be capable of growing upon drier soil. But that sequoia can and does grow on as dry soil as that occupied by either fir or pine is manifest in a thousand places along the main belt. “Why, then,” it will be asked, “are sequoias always found in greatest abundance on well-watered places where small perennial streams abound?” Simply because a close growth of sequoia always produces those streams. The thirsty mountaineer knows well that in every sequoia grove he will find running water, but it is a very complete mistake to suppose that the water is the cause of the grove being there; for, on the contrary, the grove is the cause of the water being there. Drain off the water, and the grove will remain. But cut off the grove, and the streams and springs will at once disappear."        

-John  Muir