Millions of people could be driven from their homes by the impact of climate change and the world needs to prepare, the United Nations High Commissioner for Refugees has said.

Speaking at the World Economic Forum, in Davos, the head of the UN’s refugee agency Filippo Grandi said the world community needed to prepare for people displaced by climate change.

“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.”

But potential causes include bushfires like those seen in Australia recently, 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.

Mr Grandi said that for most of its 70 years UNHCR 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,” Mr Grandi said.

The convention relating to the status of refugees, signed in 1951, makes no provision for climate change as a reason for people to flee their country and seek asylum elsewhere.

But as climate impacts grow, human rights activists say climate should be a reason for granting asylum.

Recent conflicts Iraq, Afghanistan and Syria which have forced civilians to flee has seen the number of displaced persons risen to more than 70 million.

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.

Mr Grandi said European governments needed to think hard about solutions to the migrant crisis, which has affected them since 2015,

His comments followed a UN Human Rights Committee ruling on Monday on the case of Kiribati national Ioane Teitiota, who brought a case against New Zealand after authorities denied his claim of asylum because of climate change and rising sea levels.

Effectively, the ruling says that if you have an immediate threat to your life due to climate change and if you cross a border and go to another country, you should not be sent back, because you would be at risk of your life.