Climate change is already forcing people to migrate, with most moving within their countries or to a neighboring country, a report by the International Organization for Migration said Tuesday.

While the report did not give any estimates on numbers of climate change migrants, it warned that poor countries will need international support to help them cope with the growing trend.

The study "finds that large-scale human movement from climate change and environmental degradation is not only inevitable but is already happening."

"However, much of it is internal or cross border migration, belying some fears that millions of poor people will go to rich countries as a result of climate change," added the report entitled "Migration, Environment and Climate Change: Assessing the Evidence."

In Ethiopia, Mali, Burkina Faso and Senegal, there has been "fairly common" movements of populations in response to drought, said the report.

The report also zeroed in on Senegal's Tambacounda region, where drought-related migration began as a local form of internal migration, but later moved to other neighboring African states.

While the number of people affected by natural disasters has more than doubled in recent years, there has been no corresponding rise in long-distance international migration from disaster-affected regions during these periods, it said.

But with more people and regions expected to be affected by global warming in coming years, the report warned that international support would be needed to help poorer countries cope with the movements.

It also noted that there was a "worrying lack of policies" in richer destination countries to deal with environmental migration.

"While acknowledging that the impact of climate change on migration is predominantly internal movement, international migration is nevertheless likely to be increasingly important in the future and will necessitate policy and program responses that are currently lacking," it added.

The UN refugee agency has estimated that some 24 million people worldwide have fled their homes due to environmental factors.

The IOM report noted that wide-ranging estimates of climate migrants -- from the lower figure given by the office of the UN High Commissioner of Refugees to another of 1.0 billion people by 2050, also highlights the "dearth of serious data research" on the issue.