Desert Climate:

Temperature: Temperatures vary from day to night. Typically in the day, temperatures can reach over 100 degrees, and then drop down to below freezing at night. These radical changes in temperature are due to the desert having little to no vegetation. The extreme hot temperatures in the day often cause mirages and hallucinations.
Precipitation: The Desert receives less than 25cm of rain each year. The most rain occurs in December through March, and each of those months receive up to 1.3 cm of rain. Hot deserts typically receive rain as their main source of precipitation, and cold deserts typically receive fog or snow. However, some deserts receive no rain at all, and the humidity is too high for anyone to live there.
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Overall, because of desert's positions typically located near the equator, their climate is very hot and dry. Few animals and plants can survive here because of these extreme conditions.

Competition:

Desert plants compete for water, and their usually wide spacing reflects competition of their root systems for water capture. If a patch of desert is cleared of vegetation then the same species will reappear, spaced out to exploit the available water, because these are the only species adapted to withstand the rigours of drought.

Cactus plants do not grow very close together. Their roots, however, radiate out from the cactus plant, just under the surface of the soil. The roots of a cactus need to absorb as much water as possible when it rains. In this ecosystem it is the roots of the cactus plants which compete for space below the ground.

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Human impact:

Off roading is one of the human activities that greatly hurts the desert. Many people drive their off road vehicles in unrestricted areas all over the desert. Their vehicles leave tracks on the soil, which scars the land for decades. These tracks also kill off the very little vegetation found in the desert. When vegetation dwindles in population in popular off roading areas, so does the animal population. Animals that hide in the sand can also be harmed. The sand viper, for example, which hides itself in the soil, can become an accidental victim of off roading mayhem. Mining, ranching, hunting, and collecting of various plants and animals in the desert are also human impacted harms done to the desert, for they are continuing the decrease the already little wildlife found in this biome.

Invasive Species:

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The cactus moth is a common invasive species in the desert. They are slowly destroying deserts by consuming too many cacti. They are destroying entire populations of cacti in the southwest- specifically, prickly pear populations. Their consumption of the prickly pear is affecting humans in two ways: firstly, the prickly pear is a source of food, especially in Mexico. Secondly, many farmers rely on the prickly pear as the main source of food for their livestock. Without enough, their livestock is suffering. Within their trophic level, they are destroying sources of food for other primary consumers such as deer, rodents, and cyotes. Also, the cactus moth is taking away nesting sites for certain types of birds by eating all the prickly pears. Lastly, the cactus moth is taking away sites where other native moths and butterflies lay eggs and form cocoons.
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The red imported fire ant is native to South America, but these ants were brought to the U.S. in the 30's. These dangerous ants are becoming more abundant in the deserts of Arizona. Fire ants inject a necrotising, alkaloid venom when they sting, which causes intense pain to the victim. Five million people are stung each year by these invasive desert ants. They are affecting humans in another way because of the damage to agricultural equipment, livestock, and electrical systems they cause. These ants will eat/ attack many different species of organisms (animal or plant) and they are currently destroying a variety of plants that are native to the area, causing their populations to decrease. Since these ants are imported, they are competing with native fire ants for the same resources. The imported ants are much more aggressive than the native species, so they often eliminate other native populations. They are also competing with other consumers such as cattle, causing whole herds to suffer from just one attack. Lastly, these fire ants commonly invade the nests of birds, and as a result, the young birds do not survive past infantry.

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Buffelgrass, although it appears to be harmless, is actually causing major damage to deserts everywhere. Buffelgrass grows densely and crowds out native plants of similar size. Also, competition for water can weaken and kill larger desert plants. This is especially true in the desert because there is so little water to begin with. Thirdly, dense roots and ground shading easily prevent the germination of seeds- usually of another species of plant. Buffelgrass can kill most native plants by these means alone. Buffelgrass also affects other trophic levels because it kills native plants that animals rely on as their primary source of food. Secondly, this invasive species takes water away from plants like cacti, from which several types of birds get their water. Lastly, it affects humans. This grass is spreading so quickly that it is beginning to find its way onto farms. Once buffelgrass is on a farm it is hard to completely remove all traces of it.