See the context of this sign.

Where Two Deserts Meet

To the north and west lies the wetter and higher Mojave
Desert, between 2,000 and 5,000 feet above sea level, where
you'll find abundant plant life, including vaccas, cactus?, and the
high desert's trademark, the Joshua Tree.

To the south and east lies the drier and lower Colorado
Desert, where sparser plant life grows, including creosote
bushes, ironwood, and the peculiar, spindly ocotillo.

Most animals roam freely between the two deserts, but many
plants grow only in one.

You're standing where California's two great deserts meet - but
you won't find any signpost saying "Mojave Desert This Side," or
"Colorado Desert Begins Here!" For the transition zone, between
the two is a mingling area of the ecosystems of both.

Don't miss the rest of our virtual tour of Joshua Tree National Park in 1588 images.