In this paper , there were a few minor graphical errors and omissions regarding figure 1. We have supplied the correct figure 1 with an extended caption rectifying the mistakes. The entire text of the article including results, discussion and conclusions remains unchanged as we performed the calculations on the correct raw dataset.
The corrections are: (i) it is not mentioned that we applied an interpolation to the raw data in figure 1 for the sake of visual clarity, (ii) the previous figure 1 erroneously indicated the presence of languages in large areas of the Canadian Arctic and Greenland that are known to be uninhabited, (iii) the numbering on the colour bar was not correct and (iv) it should have been mentioned that the original data source (the Ethnologue) does not annotate which languages are found in cities.
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