In other circumstances, global warming is expected to expand the size of deserts, which currently encompass one-quarter of the Earth's surface. Human activities such as firewood harvesting and animal grazing are also contributing to the conversion of semiarid zones into deserts, a process known as desertification.
In deserts where water is scarce, humans rely on irrigation for survival. Irrigation channels need to be maintained by monitoring their condition so that they can be repaired when needed. Water engineers monitor these channels for damage and repair them when necessary. Monitoring irrigation channels is an important job for farmers but also for civil engineers who design new channels and cities in arid regions.
Deserts are very hostile environments for human settlement. However, many people have found ways to live in these areas over the years. Archaeologists have uncovered evidence of early civilizations in desert regions around the world. These include evidence of farming in Israel and Jordan at about the same time the Egyptians were building their pyramids, suggesting that ancient people may have migrated to the desert to find food and shelter. Modern examples include the Beduin in Egypt and Arabia and the Navajo in North America.
People continue to live in deserts today. Many rural Africans depend on groundwater that is not safe to drink due to bacteria that grow in the soil if it remains wet for too long. Their only option is to carry this water home from distant wells.
Expansion and extensive use of agricultural areas, inadequate irrigation techniques, deforestation, and overgrazing are all examples of human activities that lead to desertification. These unsustainable land uses put immense strain on the land by changing the chemistry and hydrology of the soil. The resulting degradation can be alleviated to some degree by allowing natural processes to take place on abandoned fields or grazing lands, but this will never restore a degraded site back to its original state.
Deforestation in particular has been a major factor in the decline of the Amazonian rainforest. The buildup of carbon dioxide in the atmosphere due to deforestation is having a negative impact on global climate patterns. Deserts are expanding as a result of these changes, with serious consequences for people who live in or near these vulnerable ecosystems.
Agricultural practices have also had an effect on desertification through the use of pesticides and fertilizers that run off farmland and contribute to algal blooms in lakes and oceans which can lead to extinction via hypoxia (low oxygen levels) or acidification. Abandoned agricultural lands may eventually return to forest if no further action is taken, but it will not be able to support human life because there are no longer any effective conservation measures in place to protect it from further damage. Forests play an important role in regulating Earth's climate, providing shade and moisture where they are needed most. When they are gone, they are gone for good.
The desert's water supply is dwindling as a result of global warming and human activity. Driving a car in the desert causes irreparable habitat degradation. The implications will be severe if people do not repair the damage created by their activities in the desert. Global warming is causing deserts to dry up. This is bad for humans because it makes it harder to travel, which harms trade and interaction between societies.
Human activity has also been responsible for some drastic changes within deserts themselves. Deserts used to contain many more species of plants and animals, but this number has decreased due to deforestation and overgrazing. Mining and other forms of development have also caused major problems for those living in or near deserts. Heavy machinery can damage the soil surface, leading to erosion and flooding, while toxic chemicals are released into the environment when mines are depleted of ore.
Many scientists believe that within a few decades there will be no more rain for hundreds of miles around some desert springs. This would cause serious problems for people who live in these areas because there would be nothing growing anywhere near the spring. Without any kind of food source or animal to farm, these people would be at risk of starvation.
Some deserts are being invaded by humans themselves. Around 20 million people live in areas that were once part of the Sahara desert, because they can find work there or in cities across North Africa. This invasion has had a huge impact on the ecology of the region.
"Drought is becoming more common as a result of global warming, which dries out water holes." Higher temperatures may cause an increase in the number of wildfires, which modify desert landscapes by displacing slow-growing trees and shrubs with fast-growing grasses.
Deserts are known habitats for many species of plants and animals. But due to the arid environment, most species in deserts are specialized for living in these conditions. They do this by using strategies such as not needing much water, having small leaves, or making their bodies oil or alkali when exposed to wind or heat.
The three main types of desert are:
Wetlands - those areas that are flooded or have recently been flooded. These areas are usually fertile and support different types of vegetation including mosses, liverworts, fungi, and flowering plants. Wetlands can be divided up into two groups based on how long they remain wet: seasonal wetlands (which dry out each year) and perennial wetlands (which always contain water).
Coastal deserts - the edge of the desert where the sea meets the land. This area may include beaches, dunes, rocky reefs, or inland salt pans. Coastal deserts are found only in tropical regions near oceans or large lakes.
Rocky desert - a high plateau with very little soil and no trees.