The world needs to prepare for millions of people being driven from their homes by the impact of climate change, the United Nations High Commissioner for Refugees said on Tuesday.

Speaking to Reuters at the World Economic Forum, Filippo Grandi said a UN ruling this week meant those fleeing as a result of climate change deserved international protection, and that it had broad implications for governments.

The UN Human Rights Committee made the landmark ruling on Monday in relation to Ioane Teitiota, from the Pacific nation of Kiribati, who brought a case against New Zealand after authorities denied his claim of asylum.

We must be prepared for a large surge of people moving against their will. - Filippo Grandi, UN High Commissioner for Refugees

"The ruling says if you have an immediate threat to your life due to climate change, due to the climate emergency, and if you cross the border and go to another country, you should not be sent back, because you would be at risk of your life, just like in a war or in a situation of persecution," Grandi said.

"We must be prepared for a large surge of people moving against their will," he said. "I wouldn't venture to talk about specific numbers, it's too speculative, but certainly we're talking about millions here."

A sculpture featuring climate refugees created by Danish artist Jens Galschiot is seen at Rheinaue park during the COP23 United Nations Climate Change Conference in Bonn, Germany, in 2017. The UN says the world needs to prepare for millions of people being driven from their homes by the impact of climate change. (Patrik Stollarz/AFP via Getty Images)

Potential drivers include wildfires like those seen in Australia, rising sea levels affecting low-lying islands, the destruction of crops and livestock in sub-Saharan Africa and floods worldwide, not least in parts of the developed world.

Whereas for most of its 70 years UNHCR, the UN's refugee agency, has worked to assist those fleeing poorer countries as a result of conflict, climate change is more indiscriminate.

"It is further proof that refugee movements and the broader issue of migration of populations ... is a global challenge that cannot be confined to a few countries," said Grandi.

70 million displaced

Yet the convention relating to the status of refugees, signed in 1951, made no provision for climate change as a reason for people to flee their country and seek asylum elsewhere. As climate impacts grow, legal questions become more complicated.

UNHCR, whose budget has risen from $1.3 billion Cdn a year in the early 1990s to $11 billion in 2019 as conflicts in Iraq, Afghanistan and Syria have forced civilians to flee, now assists more than 70 million forcibly displaced people.

Demonstrators shout slogans in support of Syrian refugees during a protest against Turkish government's recent refugee policies in Istanbul in July 2019. (Murad Sezer/Reuters)

Turkey is the largest recipient, with more than 4 million refugees and asylum seekers, the vast majority from Syria. That has strained Turkey's public finances and led President Tayyip Erdogan to demand more assistance from Europe.

Last November, Erdogan threatened to open the door for Syrian refugees to head to Europe unless the European Union stepped up, and he is now calling for the "resettlement" of up to 1 million Syrians in the north of their homeland.

Grandi said European governments needed to think hard about solutions to the migrant crisis, which has affected them since 2015, but also show more understanding of Turkey's situation.

"We must recognize that, for the past several years (Turkey)has been hosting the largest refugee population in the world," he said. "There's a lot of political talk. I concentrate on the substance of this, which is 'let's strengthen Turkey's ability to host refugees until they can go back safely, voluntarily to their countries'."