Tip: See my list of the Most Common Mistakes in English. It will teach you how to avoid mistakes with commas, prepositions, irregular verbs, and much more (PDF Version).
The map below shows the percentage of land covered by tree canopy (based on data by the U.S. Geological Survey from 2010) together with man-made structures (in red, based on data by ESA). Areas that are neither red nor green represent other types of land cover, such as crops, grass, shrubs, bare rocks, and water:
It should be noted that the sharp edges visible in the Central African Republic and South Sudan are likely just the result of a combination of two different sources of satellite imagery, perhaps taken during different seasons, rather than a representation of real natural features.
By the way, I have written several educational ebooks. If you get a copy, you can learn new things and support this website at the same time—why don’t you check them out?
Where to go next? Check out the language-learning system LingQ. It is, hands down, the best currently available tool if you want to expand your vocabulary in a foreign languageI have personally learned over 70,000 words in more than a dozen languages with LingQ, and I have to say it’s the single most useful language-learning tool I have ever tried.