KATHMANDU: Effects of climate change including the melting of Himalayan glaciers threaten water and food security for more than 1.6 billion people living in South Asia, according to a study released Wednesday.

India, Bangladesh, Afghanistan, and Nepal will be most vulnerable to falling crop yields caused by glacier retreat, floods, droughts and erratic rainfall, said the study financed by the Asian Development Bank.

"South Asia's vulnerability to climate change has extremely serious implications for agriculture and therefore food security," Kunio Senga, the ADB's director general for South Asia, told a news conference in the Nepalese capital, Katmandu.

The Manila, Philippines-based bank, which finances poverty reduction programs, reported the findings Wednesday. The full report, produced by the International Food Policy Research Institute, is due for release later this month in Bangkok, Thailand on the sidelines of a U.N. climate change meeting.

The study warned if current trends persist until 2050, the yields of irrigated crops in South Asia will decrease significantly.

In the case of Nepal, Environment Ministry Secretary Udaya Raj Sharma said the rate of glacial melting in the impoverished Himalayan nation's mountains was higher than initially predicted, and the trend threatened rice and wheat crops.

A report released last week by British aid agency Oxfam warned millions Nepalese face severe food shortages because of climate change. It said changing weather patterns — extreme temperatures, drier winters and delays in summer monsoons — have dramatically affected crop production already, leaving farmers unable to properly feed themselves and pushing them into debt. An estimated 3.4 million people in Nepal need food aid, it said.

Oxfam predicted river levels will decline because of reduced rainfall and glacial retreat, making it harder to irrigate crops and provide water for livestock.