Desert ecosystems

While deserts are very foreboding places due to the dry and often hot conditions found there, they are in fact full of specially adapted plants and animals. These organisms have evolved to deal with a lack of water in a number of ways.

 

There are two main categories of desert plants: drought evaders and drought resisters. Drought evaders lie dormant as seeds for long periods of time, waiting for it to rain. When it does rain, they quickly sprout, bloom and reproduce while water is still available. The plants then die off and leave new seeds for the next time it rains. (Refer Image 1) Their seeds have special coatings that protect them from the elements. These coatings are dissolved by water when it does rain. Since drought-evading plants are not active for very long, they are sometimes referred to as ephemerals.

 

Drought resisters make the best use of the water that is available to them. There are a number of ways in which plants can do this. Many plants store water in their stems and roots. Other plants have developed special waxy skin and thin needle-like leaves that prevent evaporation through transpiration. Some desert plants also have extensive root systems that draw in water from a large area. Plants have also adapted to draw water out of dew and fog, especially in foggy coastal deserts.

 

Often, drought resisters use multiple adaptations in order to survive in the desert. Giant saguaro cacti in the Sonoran Desert store water in their fleshy stems and have spread-out root systems to gather water from a wide area. Their spiny leaves and waxy skin help the plant reduce water loss through transpiration as well as keeping hungry and thirsty animals at bay. Welwitschia plants in the Namib Desert, which is a cool coastal desert, absorb water from dew and fog and store it in a large root. (Refer Image 2) Baobab trees have expanding trunks that store large amounts of water when it rains. Drought-resistant plants like this are called xerophytes.

 

There are both carnivorous and herbivorous animals in the desert - that is, animals that eat other animals and animals that eat plants respectively. As a result, different animals use different adaptations to find food and protect themselves from both the elements and each other. Many desert animals, especially mammals, are nocturnal. This means they are asleep during the hot part of the day, often in cool underground burrows, and awake and active at night. Many reptiles, on the other hand, are active during the day because their cold-blooded bodies can tolerate the high temperatures. Reptiles are more sluggish during the night. Desert animals often have to survive for long periods without food or water, as both are difficult to find in the desert. Some snakes can survive without food for months and some insects have adapted to live without much moisture. Some animals absorb water through their skin when it falls as dew and other animals, such as the kangaroo rat, can make their own water out of the food they eat. Camels' humps are   large stores of fat, which allow them to manage for long periods of time without eating or drinking. Some animals, like toads and goannas, go months without food or water, sleeping in underground burrows during the harshest parts of the year. This is called aestivating.

 

Herbivores and carnivores alike use the ability to camouflage, although for different reasons. Herbivores use camouflage to hide from carnivores, while carnivores use it to sneak up on their prey. Prey animals have different methods for escaping from their predators. The kangaroo rat, for example, is very fast over short distances, while the mountain devil has sharp spikes to make predators leave it alone. Controlling body heat and water loss are both important concerns as well and animals do this in different ways. Many desert animals have adapted so they do not sweat or urinate much. Snakes and lizards can adapt to a wide range of temperatures due to their cold-blooded nature. The fennec fox has enormous ears that help it disperse heat and hear its prey.

In the middle of some deserts, such as the Arabian and Sahara Deserts in Africa and the Middle East, there are oases. At an oasis, water comes up from under the ground through a crack in the earth. These areas are far more fertile than the surrounding desert and plant life that could not survive in other parts of the desert is plentiful. Date palms grow at oases.

 

Desert plants and animals have a direct connection to one another. Desert plants are eaten by herbivores, while carnivores eat the herbivores. This is called the food chain.The food that a desert creature eats not only gives it energy, but it also provides the animal with most of its supply of water. In this way, water is passed from plants to herbivores to carnivores. Harm to one desert species, therefore, can harm many others. If the plants in the desert were somehow harmed,  the animals that eat the plants would have a more difficult time finding food (and the water they get from their food). Carnivores would also have a harder time finding their prey