germination of summer annual plants and supports smoketree, ironwood, and palo verde trees. Common desert wildlife include mule deer, bobcat, desert kangaroo rat, cactus mouse, black-tailed jackrabbit, Gambel's quail, and red-diamond rattlesnake. Among sensitive species are flat-tailed horned lizard, Coachella Valley fringe-toed lizard, desert tortoise, prairie falcon, Andrews' dune scarab beetle, peninsular bighorn sheep, and California leaf-nosed bat. The best place to spot wildlife is at the wetland refuges along the Colorado River, Cibola National Wildlife Refuge and Imperial National Wildlife Refuge. In the Colorado Desert's arid environment, aquatic and wetland habitats are limited in extent but are critically important to wildlife. Runoff from seasonal rains and groundwater springs forms desert arroyos, desert fan palm oases, freshwater marshes, brine lakes, desert washes, ephemeral and perennial streams, and desert riparian vegetation communities dominated by cottonwood, willow, and non-native tamarisk. Two of the region's most significant aquatic systems are the Salton Sea and the Colorado River. While most desert wildlife depend on aquatic habitats as water sources, a number of species, such as the arroyo toad, desert pupfish, Yuma rail, and southwestern willow flycatcher, are restricted to these habitats. In some places, summer rains produce short-lived seasonal pools that host uncommon species like Couch's spadefoot toad. Desert fan palm oases are rare ecological communities found only in the Colorado Desert. They occur only where permanent water sources are available, such as at springs or along fault lines, where groundwater is forced to the surface by the movement of hard impermeable rock, and can be found in the San Jacinto, Santa Rosa, and Little San Bernardino mountains, in the canyons of Anza-Borrego Desert State Park, and along the San Andreas Fault in the Coachella Valley. The only palm native to California, Washingtonia filifera (desert fan palm), grows at the oases. Endemic flora Some sub-regions of the Colorado Desert contain endemic flora. Along the Lower Colorado River Valley, in-flow side canyons, flatlands, or low-to-higher level elevations, at least three such flora occur: Hesperocallis undulata (desert lily), Nolina bigelovii (Bigelow's nolina), and Peucephyllum schottii (desert fir). National and State Parks Joshua Tree National Park Imperial NWR Sonny Bono Salton Sea NWR Indio Hills Palms Anza-Borrego Desert State Park Ocotillo Wells State Vehicular Recreation Area Picacho State Recreation Area Heber Dunes State Vehicular Recreation Area Salton Sea State Recreation Area Environmental issues The Colorado Desert is one of the least-populous regions in California, but human activities