GENEVA — Nearly 132 million people will need aid and protection in 2019, the United Nations said on Tuesday, opening an appeal for about $25 billion as more and more people are displaced by conflicts and protracted conflicts absorb most of the assistance.

Mark Lowcock, the United Nations aid coordinator, said that one out of every 70 people on Earth will need assistance next year in seeking an increase in donations of about 10 percent, even though relief agencies are becoming more efficient.

“We need to make it a bigger priority in 2019 to address the underlying causes of crises — insecurity, conflict, poverty, development failures, inadequate adaptation and resilience to climate change,” he said.

The biggest challenge in 2019 will be the three-year conflict in Yemen, which has driven millions toward famine and has given the country the status of the world’s worst humanitarian crisis. Next year, nearly 24 million people — three-quarters of the population — will need some form of assistance, Mr. Lowcock said.