President-elect Donald Trump wouldn't rule out military or economic coercion, saying the U.S. needs to stop China. Also a factor: climate change.

Global warming is making both places more important to global shipping and trade. To imagine the kind of future a hotter, dryer climate may bring, and the geopolitical challenges it will create, look no farther than two parts of the world that Donald Trump wants America to control: Greenland and the Panama Canal.

U.S. President-elect Donald Trump says he wants to make Greenland a part of the United States and does not rule out using military or economic power to get Denmark to hand over the mineral-rich and strategically important island.