Deserts generally have less water to support large populations.
moisture is lacking and organic acids are scarce
more than deserts and less than forest
The desert receives one 20th or less of the amount of water that a rainforest receives. This is because deserts get very little rain.
Water causes the greatest amount of weathering, especially flowing water. Water is scarce in deserts.
A desert is defined as a region that receives less than 10 inches (250 mm) of precipitation per year on average. Some deserts receive virtually no rainfall for years.
Deserts have less water and rainfall that speed up oxidation.
cactus need less water thus they grow in deserts
In many desert areas the water contains a high concentration of minerals dissolved from the soil and may not be safe to drink. In other deserts where the water flows from surrounding mountains the water may be purer with less mineral content. Deserts with springs that form an oasis may have water that is safer to drink.
All deserts are water deprived, that's why they are called deserts.
No life can exist without water. However, in one form (free form) or another (bound) but biochemical reaction needs water. some animals need less water while others need relatively more. If we think of plants in deserts(zerophytes) they also take water even less. In the same way animal in deserts(Zerozoites) may need water less or more as they need water for their metabolic process. As a result of metabolic process waste metabolites must produce. How waste can be excreted without water. If water gets out it then must get in to replinish and continue the life process. Now, animals in deserts may not necessarily take water in pure form but may take it bound in food depending its amount on need of the animal.
Each undisturbed desert has exactly the number of plants that can be supported with the amount of rain the region receives - nothing less, nothing more.