Desert Ecosystems

October-November 1998

This is an article from WaveLength Magazine, available in print in North America and globally on the web.

by Claire Heffernan

A bed fit for a rattle snake. Watch your step!

"Desert" is derived from the Latin word meaning "abandoned", but the desert is anything but empty. The Sonoran desert which begins in southeastern California and extends into northern Mexico and Baja contains plants, animals, birds, reptiles, insects and people and some of the best hiking, paddling and sightseeing in the northern hemisphere,

Deserts are very old landscapes approximately 10 to 12 million years old and are evenly distributed around the globe in two continuous belts - the northern hemisphere around the Tropic of Cancer and in the south around the Tropic of Capricorn. The combined arid and semi-arid regions of the world add up to 16 million square miles of the earth's 56 million square mile surface.

There are 13 major desert regions in the world and four in North America. The Sonoran desert is characterized by well defined winters and summers, lack of rainfall, low humidity and intense heat. The low humidity allows the desert to cool rapidly at night-as much as 50 degrees-an important factor in the survival of the desert's plants and animals. Desert soils are rich in minerals and very fertile so where irrigation is possible, a wide variety of crops are grown.

How do plants and animals survive this harsh environment? Many annual grasses, herbs and weeds lie dormant and sprout when there is sufficient moisture. Dessert perennials have deep tap roots to take advantage of underground water sources and widespread shallow roots to gather surface moisture from rainfall. Their sparse foliage and waxy leaves cut down on the plant's evaporation and protect them from the sun's damaging rays.

By comparison, cactus have only shallow roots that suck enormous amounts of water which is then stored on the thick body of the plant and rationed out to living tissue during periods of drought. Some desert trees have thick pulpy trunks for water storage and others shed their leaves to reduce evaporation. Some die off above ground but preserve their root bulbs underground until conditions are favourable for new growth.

Animals, birds, insects, reptiles and even people limit their activities to the cooler hours of dawn and dusk. The desert, which appears lifeless during the scorching heat of the day, becomes busy with activity as the shadows grow long over the landscape.

Lizards move about first, then birds and finally mammals emerge from their underground shelters. They include squirrels, jack rabbits, mice, kangaroo rats, coyotes, kit fox, bats and badgers. Birds include owls, roadrunners, the Gila woodpecker, vultures, doves, osprey, herons and a wide variety of ducks and waterfowl. There are ants, spiders, scorpions, cockroaches and mosquitoes. Reptiles include snakes, chuckwallas, the spadefoot toad, turtles and a wide variety of lizards.