NATO's member countries are tackling everything from rising seas to cyberattacks at a two-day conference being held at the organization's North American headquarters in Virginia.

The meeting began Wednesday in Norfolk, a city that hosts the world's largest Navy base and is confronting its own issues, including coastal flooding. A range of officials are attending, from the mayor of New Orleans to the Czech Republic's defense minister.

David O'Sullivan is the European Union's ambassador to the U.S. He said during opening remarks that environmental factors such as climate change and population growth "can destabilize entire nations and regions within our neighborhood and beyond."

He also said the U.S. and Europe must adapt to new types of warfare, including the spread of "fake news" and cyberattacks.