Introduction

Aside from human activity, climate variation is one of the principal factors causing change in the Mojave Desert ecosystem. Even though dry most of the time, the countless washes, gullies, and rills, and the vegetation associated with them attest to the importance of precipitation in the desert ecosystem. The present landscape and vegetation reflect to a measurable degree the climate variation of the past several decades. Climate affects sediment yield, frequency of surface runoff, recharge of shallow aquifers, and the recovery of the landscape from human disturbances.  Climate also influences vegetation density, establishment of invasive species, and the frequency and intensity of wildfires.