A limiting factor is an environmental factor that tends to limit population size. There are two different types of limiting factors: density-dependent and density-independent. The difference between the two is that density-dependent limiting factors rely on population size; the larger a population, the bigger impact a density-dependent limiting factor will have. Density-independent limiting factors do NOT rely on population size, instead they affect all populations equally.
Two density-dependent limiting factors include competition and disease. Both of these factors rely on the size and density of a population because it creates conflict over limited resources (competition) and the more dense a population is, the easier it is for pathogens to spread and infect many individuals (disease). A specific example of competition seen in deserts is observed within the Cactus Wren population. The Cactus Wren relies greatly on the Saguaro Cactus for food, water, and shelter. However, a Saguaro Cactus can only provide such resources for a certain number of wrens. If the population density in the ecosystem were to increase, competition over these cacti would increase, making this a density-dependent limiting factor. Only a certain density of Cactus Wren can be supported in an ecosystem. Another example of a density-dependent limiting factor is disease. In a desert, or any other environment, the more dense a certain species population is, the faster and more likely a disease is to spread. That is because organisms living closer together (more dense) spread disease very easily. Therefore, disease is also considered a density-dependent limiting factor.
Two density-independent limiting factors include temperature and weather. These two factors do not rely on the size or density of a certain population. They affect all organisms (in a population) equally. If temperature increases or decreases drastically (even more-so than the already drastic-temperatured environment), all of the organisms in a population are affected the same exact way. Whether the population consist of large and dense numbers or small and sparse ones, the organisms will all be affected. The same goes for weather conditions. If there is a huge storm, (most likely a sand-storm), all organisms will be affected. All density-independent limiting factors are essentially the same idea: an event occurs that affect all organisms equally no matter the size or density.