The Sierra Nevada Mountain range is definitely an ecosystem
that is incredibly vast, and stretches out for more than 250 miles across the
state of California. Realistically, this ecosystem has a regional scale, and is
the most important source of water for all of California and its agriculture.
Despite this however, there are very many National Parks and reserve areas that
are protected federally or conserved locally, such as Yosemite National Park,
the Sequoia National Forest, and Lake Tahoe.
(source: http://power.arc.losrios.edu/~reevesl/assignments/images/map_ca.jpg)
