In the early 21st century, the tree cover is well above that of the average tree cover of other major cities in the United States and the rest of the world, with the main species the London plane. Other species are being introduced to increase diversity and to help cope with the effects of climate change on vegetation in the future. Treepedia, a project run by MIT using Google Maps’ street-view data to calculate tree coverage in cities, ranked Sacramento the greenest city of 15 studied in the US, and third globally, after Vancouver and Singapore.