"All around the world, predictable patterns are going to result in very long-term and very immediate changes in the ability of people to earn their livelihoods," said Michele Klein Solomon of the International Organisation of Migration (IOM).
"It's pretty overwhelming to see what we might be facing in the next 50 years," she said. "And it's starting now."
People forced to move by climate change, salination, rising sea levels, deforestation or desertification do not fit the classic definition of refugees -- those who leave their homeland to escape persecution or conflict and who need protection.
But the world's welcome even for these people is wearing thin, just as United Nations figures show that an exodus from Iraq has reversed a five-year decline in overall refugee numbers.
One more angle to consider in a problem that is already extremely complex...