A report just issued by the UN University estimates that up to 50 million people could be on the move by 2010, seeking refuge from hunger, droughts, floods, and exhausted soils.
Migration on account of an abused local environment is not new. But what stands out today is the scale of the problem.
Professor Janos Bogarti is the head of the UN University's Institute of Environment and Human Security in Bonn, Germany. He says desertification, rising sea levels, flooding, and storms related to climate change could displace millions.
He's calling for a framework to be developed for handling this category of refugee which would give them the same rights as those fleeing war or oppression.
The UN report comes at a time when scientists say they see ever more signs of environmental stress caused by population pressures, pollution, and the new -- and potentially most dangerous -- phenomenon, climate change.
Climate change is believed to be based on the buildup of so-called greenhouse gases, such as carbon dioxide, which trap the heat of the sun in the atmosphere.
It's estimated that global surface temperatures have risen by an average of 0.6 degrees Celsius in the last century. But forecasts speak of a much steeper rise coming, with an increase by the end of this century of between 4.1 and 6 degrees Celsius.
Dr. Martin Schultz of the Max Planck Institute for Meteorology in Hamburg, says research models indicate rises of such magnitude.
"The new climate simulations that we have done for the forthcoming IPCC [Intergovernmental Panel on Climate Change] report basically indicate that the average scenarios -- so that is not the most pessimistic scenarios, which have often been used in the past, but really the mean scenarios -- indicate a temperature rise of the order of 4 degrees," Schultz told RFE/RL.
The institute estimates this could result in a 30-centimeter rise in ocean water levels by the end of the century because of melting ice caps.
Schultz cautions that the estimates of rising sea levels are still subject to a number of variables. But the general trend of that scenario has been reinforced by a report from U.S. scientists that the Arctic ice this summer shrunk for the fourth consecutive year, and is now at its smallest point for a century. Mountain glaciers are also measurably shrinking.
A third of a meter rise in sea water levels would submerge many Pacific island communities and low-lying areas of Asia like Bangladesh, and would drown or put at risk port cities and coastal plains everywhere in the world.
Indicating the rate of increase in extreme weather conditions, the International Red Cross and Red Crescent said in a recent report that the average annual number of natural disasters in the period 2000 to 2004 was 55 percent higher than in the previous period.
But if excessive water levels in the oceans is a potential future problem, lack of water on land is already causing environmental strains. Per Bertilsson, of the Stockholm International Water Institute, says increased climate variability would have severe consequences. "Additional periods of drought, for example, will have a negative impact on food production in particular," he told RFE/RL.
Bertilsson calls for wiser use of the earth's precious water resources at a time of increased uncertainty over the climate. He says much water is wasted today because of inefficient management practices, as well as pollution:
"Food production -- that is, agriculture -- uses approximately 70 percent of all water, and if we can improve the efficiency of irrigation practices, there is a lot that can be gained," Bertilsson said.
Exactly what is expected to happen in the different regions of the world is not yet clear, but Schultz of the Max Planck Institute says scientific speculation has begun:
"That is actually the process that is just starting now -- that is, the regionalization of the results. People are now starting more detailed calculations with finer-scale models to resolve things like precipitation pattern changes and things like that," Schultz said.
Schultz says there is no way to avoid world temperatures rising. But many say the extent of the increase will depend on the will of the international community to put a brake on the spiraling production of the greenhouse gases they say is tied to global warming.