Fig. 2
Global accessibility layers. Maps show travel time to the nearest human settlement in the year 2015 for three of the nine accessibility layers, (a) for settlement class 1 (>=5,000,000 and <50,000,000 people), (b) for settlement class 5 (>=100,000 and <200,000 people), and (c) for settlement class 9 (>=5,000 and <10,000 people). Country boundaries are from GADM v3.6.
