• Known for being brutally hot and barren, deserts actually are rich and diverse ecosystems.desert 8 image by Dusan Radivojevic from Fotolia.com
  
  Deserts cover approximately 20 percent of the Earth's surface and are home to roughly 500 million people, many of whom depend on the environment for part or all of their livelihoods. Despite the lack of rain and extreme temperatures, deserts support rich ecosystems of unusual plants and animals. However, many of the world's deserts are now threatened by climate change, development, overpopulation, pollution and the destructive practices of the mining and agriculture industries. Only the most remote deserts have escaped the effects of human activity and some of the world's most famous deserts now face significant challenges that may forever change these unique places.
  
  

The Gobi Desert

• Eroded topsoil in the Gobi causes vast sandstorms across Asia.curvy dunes image by paul benefield from Fotolia.com
  
  Located in central Asia, the Gobi Desert covers 500,000 square miles of northern China and southern Mongolia. For years, livestock has grazed on the desert's dry, grassy plains, depleting vegetation and damaging fragile topsoil. The lumber-hungry construction industry has razed its forests and farmers have diverted streams to irrigate crops, a practice that increases the salinity of the soil by allowing redirected water to wash salt along new routes.These factors and others have eroded the Gobi Desert's increasingly dry and barren surface, and for the past 20 years winds have carried storms of its sand and dust across Asia, creating an average of 1,200 miles of new desert each year.
  
  

The Mojave Desert

• An unbridled tourism industry has taken a toll on the Mojave Desert's resources.Mojave Desert 5896 image by St Clair Photography from Fotolia.com
  
  More than 100 unique species of plants, including the well-known Joshua Tree, grow in the 25,000-square-mile Mojave Desert that stretches from California to Nevada, and from Arizona to Utah. Wildlife there includes owls, deer and endangered mountain lions, and the landscape features geological wonders like Death Valley. Aggressive attempts to industrialize the desert are now threatening the Mojave, which already hosts several military bases, tourist resorts and gold mines. Conservationists stopped plans for a nuclear waste dump in the desert but now dozens of investors want to build utility-scale solar energy farms there--a 600-turbine wind farm is scheduled to go online in 2015.
  
  

Sonoran Desert

• iguana image by Wimbledon from Fotolia.com
  
  The Sonoran, the largest and hottest desert in North America, covers 120,000 square miles in California, Arizona and Mexico. Development, tourism and farming are threatening the Sonoran Desert, which has the most biologically diverse desert ecosystem in the world. New construction has compromised habitats and depleted resources. Farming has introduced nonnative species of grass that threaten to overtake and eliminate indigenous plants. Grazing livestock has damaged vegetation, particularly habitats along the banks of the Gila River, and dams and water-diversion programs have changed the composition of soils. Wildlife is also at risk from poachers who take reptiles like iguanas and Gila monsters to sell to the exotic pet market, and hunters who target endangered species.