The International Organization for Migration working definition:
“Environmental migrants are persons or groups of persons who, predominantly for reasons of sudden or progressive change in the environment that adversely affects their lives or living conditions, are obliged to leave their habitual homes, or choose to do so, either temporarily or permanently, and who move either within their country or abroad.”
There is no standard definition and no such a category of refugees currently exist under international law....environmental migrants have no specific protections and governments have no agreed upon guidelines to follow. At least 26 million people around the world have already been displaced, and that figure could balloon to 150 million by 2050, according to the Worldwatch Institute.
The current administration has changed the United States’ policy concerning refugees. The total number of refugees admitted into the United States will be capped during the 2017 fiscal year at 50,000, down more than half from the current level of 110,000.