I was trying to find a definitive source on whether or not to capitalize "rainforest" when it follows "Amazon" in the Amazon rainforest. Wikipedia seems to have it not capitalized, though they strangely capitalize "Amazon Jungle". I went to look for "Sahara desert" and came across the same phenomenon. Many sources seem to not capitalize the second word in these two examples.
Other rainforests and deserts (such as the Daintree Rainforest and the Mojave Desert) seem to be rather uniformly capitalized.
Are these two different because their names are "the Amazon" and "the Sahara" as opposed to "the Amazon Rainforest" and "the Sahara Desert"?