It is part of the Mediterranean forests, woodlands, and scrub biome, with cool, wet winters and hot, dry summers.

The ecoregion contains areas of grass, chaparral shrublands, savanna dotted with oak, oak woodlands, serpentine soil communities, closed-cone pine forest with small patches of mountain conifers, wetland, marsh, salt marshes, and riverside forest.

This kind of vegetation relies on the incessant fires for germination as it clears the land and allows for shrubby growth.

The pine and cypress communities on the areas of serpentine soil within this ecoregion harbor many endemic species such as milkwort jewelflower.

The salt marsh harvest mouse (Reithrodontomys raviventris) is also included, which is the most populated endemic mammal species in U.S. and Canadian habitats.

As human activity increases the frequency of fires, the chaparral's ability to renew itself decreases, leading to elimination and degradation.

Moreover, non-native grasses will invade burned areas, making it increasingly difficult for healthy chaparral to grow.

California state policy has also recognized the need to protect the chaparral vegetation threatened by the fires.