While there were fewer than 20 cities of 1 million or more people a century ago, 450 such cities exist today, the researchers note. And even though such cities cover less than 5 percent of Earth’s land surface, they have a significant environmental footprint. “The way cities have grown since World War II is neither socially or environmentally sustainable, and the environmental cost of ongoing urban sprawl is too great to continue,” Karen Seto of Yale University said in a statement.
It doesn’t have to be this way. Curtailing sprawl and bolstering urban ecosystems will go a long way toward addressing those issues. And as Jon Christensen points out, cities are “humanity’s and nature’s only hope.”