The definition of a desert according to most sources about science is an area that has below a certain level of rainfall, but that definition can be confusing. Antarctica is considered a desert. Not only does it have very low rainfall despite being very snowy, if you see photos of areas of it without snow, it looks very barren and dry and wasteland-like-like a desert. The low rainfall does affect the vegitation and soil over there. http://en.wikipedia.org/wiki/McMurdo_Dry_Valleys Arctic tundra, by some people (not all) is considered desert because of low rainfall-but other sources I've read classify it as a separate biome from a desert, because the way that the low rainfall of a tundra affects the vegetation is different from the way the low rainfall affects vegitation in a hot area. The amount of rainfall you need for vegetation differs with temperature. Tundras have green grass and moss, and ground and vegitation is far more moist than what you'd call a "desert". The Tabernas area of Spain, WA state channeled scrublands, and eastern high plains of Colorado, are areas that some people do, and others dont, classify as deserts. Some say they are deserts because of low rainfall, while others say they arent deserts, because the amount of rainfall being low isnt severe enough to be called a desert. If thats the case, at what point does low rainfall turn into a desert? The Kau Desert of Hawaii and Highlands of Iceland and the Rangipo region of New Zealand have rainfall that doesnt absorb into soil and vegitation very well. The way the rainfall affects the soil (not absorbing that much) affects the area the same/similar way it would affect a desert-but the rainfall isnt lower that it is in any other normal area. Classifying those regions as a desert would be hard to decide.
So what, if any, is the question? At the moment, almost all of California can be designated "desert" with the severe lack of rainfall.
The question is what defines a desert. Mere rainfall itself doesnt define a desert, since as you said, many areas have low rainfall and arent classified as desert.
It's a complicated issue. The US Geological survey says the following in one of their websites: http://pubs.usgs.gov/gip/deserts/what/
Another view one could take is lack of plants (biomass), but the ground has to be exposed rock or sand, not ice. There are several different types of deserts, and each desert biome is somewhat unique. Some desert biomes have plant life, others are almost completely barren. I suppose that a desert has to have some barren exposed surface, not all covered with plants. Except in the extreme far north, tundra tends to be covered with low-lying plant life, which is highly seasonal. Some of the area in places like Nunavut are pretty barren. There may be ice and water, but too cold for much plant life. There's plenty of gravel everywhere, a legacy of glaciers during the ice age. The cold also makes it difficult for lichen to break down the exposed rock, meaning no soil. Maybe some types of plants could grow if there was some soil. There are some places in Nunavut that are just barren rock, no ice, no water, no plants. One might call this a "northern desert". A small amount of snow does fall, but it usually does not stay long and sublimes away during the day in the cold dry air. Here's a completely barren tundra in Iceland: http://images.nationalgeographic.co...and-volcanic-rift-road-trip_32549_600x450.jpg I am not sure this is a "real" desert because I think some tundra plant life could take hold if there was just some soil to grow in.
I look at the huge expanses of sand called deserts and see how very little living creatures they contain. On the other hand, if one knows what to look for, there is lots of life in places like the Sonora and Mojave deserts. Spend the night in one and you will wonder at how much there is.
If your definition of a desert is an area barren of plant life, why is the Mojave and Chihahuan regions desert? Theres some plants there.
