Climate change could cost South Asian countries nearly 9 percent in economic activity annually if fossil fuel consumption rates remain unchanged by 2100, according to the Asian Development Bank.

The climate-change study released Tuesday would affect Bangladesh, Bhutan, India, the Maldives, Nepal and Sri Lanka, which together account for 1.43 billion people. The 9-percent economic loss assumes fossil fuel use continues unabated, resulting in a 4.6 degree Celsius global temperature rise by the end of the century.

But if international agreements to curb greenhouse gas emissions resulted in keeping temperatures from increasing more than 2 degrees Celsius — as is the aim of climate talks scheduled for next year in Paris — economic losses would hit just 2.5 percent per year by 2100.

“South Asia’s economy is under serious threat and the lives and livelihoods of millions of South Asians inhabiting the region’s many mountains, deltas and atolls are on a knife edge,” said Bindu Lohani, the organization's vice president for knowledge management and sustainable development. “Countries must respond individually and collectively to cope with rising sea levels, disrupted water, food, and energy supply and increased disease.”

Much of the damage would occur through rising sea levels, putting flood-prone Bangladesh and the Maldives in precarious situations. Agricultural productivity would take a hit through changes in precipitation patterns, posing food security concerns — though some countries, like Nepal, may benefit. Shifting precipitation also might make hydropower less reliable, and higher temperatures could make diseases like malaria more prevalent.