Urban Areas

Megacities (cities with more than 10 million people) are increasing in number as the global human population continues to become more urban. By the end of 2030, three-fifths of the world population will be living in urban areas (Brennan 1999). Much of this urban growth occurs outside defined city boundaries and the resulting expansion of urban or "built-up" areas can be readily observed from orbit.

The database of astronaut photographs taken since the 1960s offers important baseline data for comparing and calculating the increases in urban areas (Robinson et al. 2000a).
 

Crew Earth Observations on the Space Station will focus on documenting the growth of the largest and fastest growing cities around the world.

 Smog
 Coral Reefs