More than 140 million people in Africa, Latin America and South Asia could move to another part of their country by 2050 to escape the worsening impacts of climate change - unless urgent action is taken to curb global warming and help people adapt, the World Bank said Monday.

Globally, the numbers of people forced to leave home because of water shortages, crop failures, sea-level rise, storm surges and other climate threats are likely to be much higher, researchers said.

But if global warming is effectively kept to limits set in the Paris Agreement on climate change, and people are helped to adapt, then the numbers migrating in the three regions will drop to about 40 million people, the study predicted.

"We have a small window now, before the effects of climate change deepen, to prepare the ground for this new reality," the head of the World Bank, Kristalina Georgieva, said in a statement.

More than 85 million people could leave home by 2050 in sub-Saharan Africa, 40 million in South Asia, and 17 million in Latin America

That preparation needs to include making economies less vulnerable to climate change, helping farmers adapt their growing techniques, and making city infrastructure more resilient to storms, rising sea levels, floods or drought, the study noted.

Cities also need to create enough jobs, and boost health and education services, to meet the needs of the growing number of people migrating to urban areas.

Without that preparation, cities could face serious repercussions, said Kanta Kumari Rigaud, who led creation of the World Bank report.

"We could see increased tensions and conflict ... but that doesn't have to be the future," the environmental specialist said. "It won't be a crisis if we plan for it now."

In the worst case scenario, more than 85 million people could leave home by 2050 in sub-Saharan Africa, 40 million in South Asia, and 17 million in Latin America, the report noted.

And the number of climate migrants could accelerate after 2050, unless there is urgent action to hold global warming to below 2 degrees Celsius above pre-industrial levels, the report noted.

The most vulnerable people, however, will be unable to move and will remain trapped in increasingly unviable areas, it predicted.

WITHIN BORDERS

Many more people are migrating within their own countries than across borders, doing so for economic, social, political and environmental reasons, the World Bank report said.

In 2016, storms, floods and other weather-related disasters - not all of them driven by climate change - forced 23 million people to move within their countries, according to the Internal Displacement Monitoring Centre.

"Although cross border movement is much more attention-grabbing and can appear more dramatic, right now the internal movement of people forms the bulk of what's going on," said Alex Randall, coordinator of the UK-based Climate and Migration Coalition.

Migration is not necessarily a bad thing, he said, and can be a good way to adapt to climate change and improve people's lives.

"It can be a positive, empowering experience. But it comes with risks as well. The emphasis should be on how we make migration safe," he told the Thomson Reuters Foundation.

CITY "HOTSPOTS"

Although much migration is likely to take place from the countryside to urban areas, cities themselves will grapple with climate impacts as well.

For example, Dhaka in Bangladesh and Dar es Salaam in Tanzania are particularly vulnerable to rising sea levels and storm surges. Addis Ababa in Ethiopia, by comparison, could see slower population growth as it relies on increasingly unpredictable rainfall, the World Bank study noted.

Regions and cities that are likely to attract large numbers of climate migrants include Nairobi, the southern Indian highlands between Bangalore and Chennai, and the central plateau areas around Mexico City and Guatemala City.

But lack of clear data about how a particular area will be impacted by climate change, and when, makes it difficult for cities, governments and communities to plan.

Nonetheless "(it's)important to help people make good decisions about whether to stay where they are, or move to new locations where they are less vulnerable," Georgieva said.

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