A biogeographical break occurs at Point Conception in central California, separating the cold temperate Oregonian Province to the north from the warmer Californian Province to the south. The link between land and sea is strong. Moisture, as precipitation and fog, comes from the sea to define and shape coastal plant communities.
Coniferous forests cover northern shores from the Olympic peninsula to the California redwoods.
Panoramic beaches, rolling grasslands, and coastal bluffs covered in sage and lupine break the forest canopy at Point Reyes and San Francisco's Golden Gate. South of Point Conception, the Mediterranean dry-summer subtropical climate produces scrub oak woodlands and chaparral. Rivers carry nutrients and sediment from distant watersheds into the coastal zone. Oceanic upwelling along the coast, driven by winds created by thermal differences between the land and sea, brings nutrients from the deep ocean into the sunlight of the coastal zone. The biological productivity of rich coastal waters supports long food chains that reach back up the rivers to their headwaters.