with 6.5 billion people currently living on the planet, it's estimated that world population mapeak at around 9.1 billion in the next 50 yrs. scientists predict that climate change linked to greenhouse-gas emissions will lead to changes in the global environment, including a rise in ocean levels. in developing nations, the majority of population growth is projected to take place in cities. many of these cities are situated in low-lying coastal areas -- eas most at risk for climate-change effects. balk: we know climate change will lead to sea-level rise, and that, of course, will affect coastal dwellers more than others. but we also know that it will increase storm surges and flooding coastal in nature. in fact, we found that coastal ecosystems were disproportionately urban and disproportionately dense in both urban and rural areas. and therefore, we became particularly interested in trying to estimate the population and the urban population that would be at greater risk of the consequences of climate change. narrator: deborah balk incorporates spacial data and methods to assess populat