Portland Metro Council President David Bragdon, says that mass migrations caused by climate change “the potential wild card” in the planning effort to ensure Oregon’s biggest city has the capacity to accommodate growth expected in the coming decades.

Droughts, wildfires, hurricanes and tornadoes all present risks in other parts of the U.S. and Oregon, which already accepts 20,000 migrant Californians a year, is worried about what happens if that population suddenly explodes with large numbers of refugees from other parts of the country .