One resource has scarcity in its name: rare earth metals. Early researchers called them "rare" because of their scattered distribution and the difficult task of mining them. Ironically, they are fairly common in the Earth's crust.
Economic and political factors constrain supply, which puts rare earths high atop the list of strategic concerns. China produces almost all the world's rare earths. The U.S. might need up to 15 years to begin mining its own deposits, according to a 2010 General Accountability Office study.
Rare earths have magnetic and other properties that make them critical to mobile phones, computers and advanced weaponry. Low-carbon energy technologies depend on them, too -- nuclear, solar, wind, biofuels, carbon capture and storage, and electricity transmission. Potential shortages are a risk to clean energy development.
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