Final answer:
About 53% of U.S. citizens live in coastal counties, making them vulnerable to rising sea levels. These areas are at significant risk of flooding, which could impact large urban populations, especially in essential port cities.
Step-by-step explanation:
Percentage of U.S. Citizens Living in Coastal Counties
The question refers to the percentage of U.S. citizens living in coastal counties who are vulnerable to rises in sea level. The correct answer is D) 53%. Considering the impact of global warming, this is significant because coastal areas are more susceptible to flooding due to rising sea levels. For comparison, we can see that other parts of the world such as Bangladesh are extremely vulnerable to sea level rises, where a three-foot increase could flood half the country.
Coastal counties in the United States are similarly at risk. Major urban populations, especially in port cities essential for trade, may face significant threats from even a modest rise in sea levels. It's also important to note that while the present rise of roughly 0.25 meters doesn't always cause problems on normal days, the additional effects of storm surges can result in detrimental impacts to human structures.
As sea levels continue to rise around the world, the geographical landscape of many coastal regions is changing. Areas that are shown in red on certain world maps indicate locations that could be underwater with a 6-meter rise in sea level, affecting infrastructure and livelihoods significantly.