California is one of the richest and most diverse parts of the world, and includes some of the most endangered ecological communities. California is part of the Nearctic ecozone and spans a number of terrestrial ecoregions.
California's large number of endemic species includes relict species, which have died out elsewhere, such as the Catalina Ironwood (Lyonothamnus floribundus). Many other endemics originated through differentiation or adaptive radiation, whereby multiple species develop from a common ancestor to take advantage of diverse ecological conditions such as the California lilac (Ceanothus). Many California endemics have become endangered, as urbanization, logging, overgrazing, and the introduction of exotic species have encroached on their habitat.
California boasts several superlatives in its collection of flora: the largest trees, the tallest trees, and the oldest trees. California's native grasses are perennial plants. After European contact, these were generally replaced by invasive species of European annual grasses; and, in modern times, California's hills turn a characteristic golden-brown in summer.
Rivers
The two most prominent rivers within California are the Sacramento River and the San Joaquin River, which drain the Central Valley and flow to the Pacific Ocean through San Francisco Bay. Two other important rivers are the Klamath River, in the north, and the Colorado River, on the southeast border.
California's large number of endemic species includes relict species, which have died out elsewhere, such as the Catalina Ironwood (Lyonothamnus floribundus). Many other endemics originated through differentiation or adaptive radiation, whereby multiple species develop from a common ancestor to take advantage of diverse ecological conditions such as the California lilac (Ceanothus). Many California endemics have become endangered, as urbanization, logging, overgrazing, and the introduction of exotic species have encroached on their habitat.
California boasts several superlatives in its collection of flora: the largest trees, the tallest trees, and the oldest trees. California's native grasses are perennial plants. After European contact, these were generally replaced by invasive species of European annual grasses; and, in modern times, California's hills turn a characteristic golden-brown in summer.
Rivers
The two most prominent rivers within California are the Sacramento River and the San Joaquin River, which drain the Central Valley and flow to the Pacific Ocean through San Francisco Bay. Two other important rivers are the Klamath River, in the north, and the Colorado River, on the southeast border.
