The Sierra Juárez and San Pedro Mártir pine–oak forests occupy the higher Peninsular Ranges to the north, where a number of tree species are found including the near-threatened California fan palm.

Although rainfall is low, the Pacific Ocean provides some humidity and moderates the temperature compared to the Sonoran Desert, which lies on the east slope of the Peninsular Ranges.

The ecoregion is mostly covered by xeric shrubs, which create varying associations based on elevation and soil conditions.

The ecoregion has close to 500 species of vascular plants, of which a number are endemic, for example the Boojum tree (Fouquieria columnaris) or Creeping Devil (Stenocereus eruca).

The San Quintin kangaroo rat (Dipodomys gravipes) and Baja California rock squirrel (Otospermophilus atricapillus) are endemic to the ecoregion.