Desert Ecosystem

A desert ecosystem is the whole community of plants, animals and tiny living things that live together in a desert. Even though deserts look empty, they are full of life, with every species playing a part in a tightly connected system. The big problem for every desert ecosystem is water, and almost every relationship between species in a desert is shaped by how they share and find water.

  • ProducersCacti, grasses, lichensPlants that make food from sunlight
  • Primary consumersInsects, kangaroo rats, desert tortoiseEat plants
  • Secondary consumersLizards, snakes, owls, foxesEat the plant-eaters
  • Apex predatorsCoyote, golden eagle, pumaTop of the food chain
  • DecomposersBeetles, fungi, bacteriaRecycle dead matter
  • Most fragileBiological soil crustA living layer that can take centuries to recover

How does desert biodiversity compare?

Plant species per km²
Rainfor.approx. 750
Temp.fstapprox. 125
Sonoranapprox. 80
Saharaapprox. 5

The wetter Sonoran Desert is far more biodiverse than the bone-dry Sahara. Tropical rainforests, by contrast, have many times more species than even the richest desert.

What is a desert ecosystem?

An ecosystem is a community of living things (plants, animals, microbes) plus the non-living things they depend on (water, soil, sunlight, weather). In a desert ecosystem, water is the most important non-living factor; how much water is available, when, and where, controls everything else.

Desert ecosystems tend to have fewer species than other ecosystems, but the species that do live there are often unique and incredibly well-adapted. A small change in any part of the system (a missing predator, an introduced species, more or less water) can cause big knock-on effects through the whole community.

The desert food chain

Like all ecosystems, deserts have food chains that flow from sunlight up to top predators.

  • Producers capture energy from sunlight. In deserts these are mostly cacti, grasses, shrubs, hardy trees like mesquite and acacia, and tiny lichens and algae.
  • Primary consumers eat the producers. Desert herbivores include insects (especially ants and beetles), small mammals (kangaroo rats, rabbits, ground squirrels), desert tortoises, and large herbivores (oryx, camels, gazelles).
  • Secondary consumers eat the herbivores. These include reptiles (rattlesnakes, monitor lizards, geckos), birds (roadrunners, owls), and smaller mammals (fennec foxes, kit foxes, sand cats).
  • Top predators sit at the top of the chain. Coyotes, golden eagles, pumas (in North America), leopards and jackals (in Africa and Asia), and dingoes (in Australia).
  • Decomposers recycle dead plants and animals back into the soil. Beetles, fungi and bacteria all play this vital role.
Fact Almost every desert plant gets started in life under the shade of an older plant called a nurse plant. The nurse plant's shade lowers the soil temperature, holds in moisture and protects the seedling from being eaten. A young saguaro cactus, for example, usually grows under a palo verde or mesquite tree.

The biological soil crust

One of the most amazing features of desert ecosystems is the biological soil crust, a thin living layer that covers much of the desert ground between bigger plants. The crust is a community of cyanobacteria (microscopic blue-green algae), lichens, mosses and fungi all woven together. The crust helps hold the desert soil in place, takes nitrogen from the air and fixes it into the soil (acting like a natural fertiliser), captures and holds water, and provides habitat for tiny animals.

Biological soil crust is extremely fragile. A single footstep can destroy years of growth. Off-road vehicles, cattle hooves and feral animals can wipe out enormous areas in a single season. Once destroyed, the crust can take 50 to 250 years to recover. Many modern desert reserves now have strict "stay on the path" rules to protect it.

How the rain shapes everything

Desert ecosystems run on the rare rains. Most desert plants and animals time their lives to match the rainfall. After a rain, the desert can bloom with wildflowers, insects, frogs and birds in a sudden burst of activity. The Atacama's "desierto florido" and Western Australia's wildflower spectacular are world-famous examples. The next dry years can then be quiet for the same species, with many surviving as seeds, eggs or dormant adults.

Did you know? Some desert plants have seeds that can stay dormant in the soil for over 50 years, waiting for the right combination of rain, temperature and light to germinate. When conditions are finally right, the entire desert can suddenly burst into colour with plants that have not been seen for decades.
Deeper dive: desert ecology, keystone species and the impact of invasive species

Desert ecology is shaped by a few basic principles. Pulsed productivity: deserts produce very little biomass for most of the time but produce enormous amounts after rare rains. Many species have evolved to exploit these pulses with explosive reproduction, then either retreat back to dormancy or migrate elsewhere. Limited carrying capacity: the desert can only support a small number of large animals because food and water are so limited. Populations of large herbivores can swing dramatically with rainfall, leading to boom-and-bust patterns. Spatial patchiness: even within a single desert, productivity varies hugely by location. Oases, dry stream beds (wadis or arroyos), north-facing slopes (in northern hemisphere deserts) and other moisture-collecting locations support far more life than the average desert area, and many desert animals concentrate their activity around these patches.

Keystone species are species whose loss would change the desert ecosystem disproportionately. In the Sonoran Desert, the saguaro cactus is a keystone: hundreds of other species use it for food, shelter or nesting, including bats that pollinate it, birds that nest in holes carved by woodpeckers in its stems, ants that protect it, and small mammals that eat its fruit. In Australian deserts, the bilby (a rabbit-sized burrowing marsupial) is a keystone: its burrows are used by dozens of other species when it abandons them, and its digging turns over the soil and improves water infiltration. The loss of keystone species can cause cascade effects through the whole ecosystem.

Modern deserts around the world face significant pressure from invasive species. In American deserts, introduced cheatgrass and buffelgrass create dense flammable mats that carry catastrophic fires through landscapes that were not adapted to fire. The fires kill cacti and native shrubs that cannot regrow. The bare ground that results is colonised by more grass, locking in the new fire regime. In Australian deserts, introduced cats and foxes have driven dozens of native marsupial species to extinction or near-extinction. In African deserts, introduced donkeys, goats and (in some areas) cattle compete with native antelopes and damage the vegetation. The "rabbit plague" of Australia produced one of the most dramatic invasive-species impacts ever recorded, and ongoing efforts to control these invasions remain a central focus of desert conservation worldwide.

For specific desert ecology examples, see desert animals and desert cactus. The opposite of healthy desert ecology is desertification.