The Asian Development Bank says climate change is likely to become a key cause of migration in Asia in the coming decades.
In a new report, the bank says more than 42 million people in the region were displaced by environmental disasters over the past two years alone.
In 2010, it said, more than 30 million people were displaced, some permanently, primarily by devastating floods in Pakistan and China.
In a video statement posted on the bank's website, Asian Development Bank Director Bart Edes said that "the fact that we see people displaced now and many of them becoming migrants gives us a taste of what is to come as climate change begins to have a greater impact."
"So we are releasing this report to present governments with policy options, with actions that they can take to address this challenge and to turn migration, climate-induced migration from a threat to an opportunity," Edes said.
The report predicts that widespread land degradation, water shortages, and desertification are expected to affect many parts of Central Asia.
The region has already experienced some of the world's most dramatic environmental crises of recent years, with water problems predominant among them.
The shrinking of the Aral Sea and the decline of two major rivers feeding the sea -- the Amu Darya and Syr Darya -- has led to significant environmental changes in the region.
At the beginning of the millennium, a drought associated with environmental degradation prompted some 250,000 people, or 20 percent of the total population, of Karakalpakstan -- an Uzbek autonomous republic surrounding the southern end of the Aral Sea -- to migrate to Kazakhstan and Russia in search of better economic opportunities.
The report says poverty and problems of governance further add to the vulnerability of local populations to environmental disasters -- such as drought, a loss of agricultural productivity, and resulting food insecurity.
The report notes that a study conducted in Karakalpakstan indicated that nearly half of the respondents wanted to migrate due to poor environmental conditions.
The report said a large part of Central Asia's population lives in areas at high risks of increased water shortages caused by climate change.
The report stresses that the impact of climate change in Central Asia is worsened by a high degree of social and economic vulnerability. Poverty is widespread, average incomes are low, and governance is often weak. Many people rely on agriculture for livelihood.
In Kazakhstan -- the region's most prosperous country -- the report says the biggest risk from climate change is what it calls "drying," which would contribute to erosion and desertification.
It says such "drying" will also contribute to a rural to urban migration of people who are dependent on agriculture for their livelihoods.
Kazakhstan has already experienced considerable rural-urban migration due to poverty and a lack of economic opportunities in villages.
In Tajikistan, about 95 percent of the country is vulnerable to floods, mudslides, water and soil erosion, and desertification, the report says.
It predicts that constantly rising temperatures in Tajikistan may further shift the existing pattern of glacier volume -- potentially leading to a widespread decline in water availability by more than 30 percent.
The report predicts that water shortages will stimulate outward migration from the affected areas.
Hundreds of thousands of people from Central Asia leave the region every year to seek work in Russia and other countries. The report says migration plays an important role in the development of the region, notably through remittances.
The report urges governments to mitigate the impact of climate change on migration flows by embracing adaptive measures and new development strategies.
It also emphasizes the need to protect migrants' rights during environmental upheavals.
Kyrgyzstan and Tajikistan have both adopted the 1990 International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families. Kazakhstan is considering ratification.
Established in 1966, the Asian Development Bank describes itself as a major source of development financing for the Asia-Pacific region, with more than $17.5 billion in approved financing.
With dpa reporting