Environmentalists want Biden's Environmental Protection Agency to aggressively regulate huge piles of toxic coal ash across the nation. The waste has polluted groundwater in 39 states.

Landfills are among the nation's largest sources of methane, a greenhouse gas far more potent than carbon dioxide. But accurately measuring methane is a major challenge to reducing it.

The Florida governor has made the environment a priority, dedicating millions to water quality and coastal infrastructure. But critics say he ignores the biggest threat: carbon emissions.

In Florida, officials fear widespread confusion when stay-at-home policies conflict with evacuation orders, and they worry about the coronavirus spreading in crowded shelters.