The desert may seem like a barren landscape, with little life and even less activity. But further investigation of the ecosystem will reveal a vibrant food chain with a variety of adaptations that allow for life in these harsh conditions.
The Food Chain
The food chain in any ecosystem is more like a food web. Plants and animals all need energy to survive. They obtain this energy through food. All organisms are designed to consume certain kinds of food. We can divide these organisms into three categories: plants, herbivores and carnivores.
Plants are the first organisms in the environment to produce energy and are referred to as primary producers. They attain energy from sunlight and convert it into carbohydrates that are used for growth and maintenance. This process is called photosynthesis. Plants are the most abundant food source in any ecosystem. Because their energy is needed to support not only the animals that consume them directly, but also the animals at the top of the food chain, they must contain an abundant supply of energy in the form of carbohydrates.
In a desert ecosystem primary producers have ample sunlight to use for energy, however, water resources are often scarce and reduces the rate of photosynthesis. This limits their ability to grow and reproduce. For this reason, desert ecosystems contain less abundant plant life than more fertile ecosystems such as rain forests.
Herbivores are animals that consume plants. The energy they gain from the plants they consume is much less than the amount of energy originally acquired by the plant. Between 15 and 70 percent of the energy attained through sunlight is used for plant maintenance and respiration. The remaining energy is all that is left for herbivores to use.
Due to the scarce plant supply, desert ecosystems cannot support a large population of herbivores. Desert land is the least productive in terms of plant growth and animals that rely on plants for survival are smaller than in ecosystems with more resources. Rodents are very common in the desert ecosystem. Their smaller bodies require less food resources to support.
Animals that prey on rodents and other herbivores are the third category in the food web. These animals are called carnivores and gain an even smaller amount of the energy that was originally introduced into the ecosystem through photosynthesis. The animal that is consumed contains hair, bones and other indigestible material that is of no use to the carnivore. On average, the consumption of another animal provides a carnivore with 5 to 20 percent of the energy of that animal. Carnivores in a desert ecosystem include foxes, snakes and birds of prey.
Organisms must adapt to survive in a habitat as harsh as the desert, where water is scarce and the daytime temperatures are high. Plants adapt by increasing their rate of production per unit of water. Production of carbohydrates by plants in habitats with limited water availability will increase by 0.4 g of mass per kilogram of water.
Animals have adapted to the hot temperatures and low water availability in several ways, including nocturnal behavior. In addition to smaller animals dominating the landscape, carnivores in desert ecosystems require less water on average than those in other environments. When low on water, animals like coyotes or foxes will consume more food, retaining what water resources may be contained in them and using specially adapted low metabolic rates to prevent further water loss from the extra digestion.