VATICAN CITY — Pope Francis said Thursday that migrants and refugees have “enormous potential” to help society if they are given a chance.

In his message for the World Day of Migrants and Refugees, issued May 12, the pope said history showed that new arrivals played a “fundamental role” in social and economic growth.

“This continues to be true in our own day. Their work, their youth, their enthusiasm, and their willingness to sacrifice enrich the communities that receive them,” he wrote.

“Yet this contribution could be all the greater were it optimized and supported by carefully developed programs and initiatives. Enormous potential exists, ready to be harnessed, if only it is given a chance.”

The World Day of Migrants and Refugees, instituted in 1914 by Pope Pius X, is celebrated annually on the last Sunday in September. This year it falls on Sept. 25.

The theme of the 108th World Migrant and Refugee Day is “Building the Future with Migrants and Refugees.”

In his 1,200-word message, dated May 9, the pope described the presence of migrants and refugees as both “a great challenge” and “an immense opportunity.”

He noted that migration had enriched Catholic communities around the world.

“As we have seen, the arrival of Catholic migrants and refugees can energize the ecclesial life of the communities that welcome them,” he said. “Often they bring an enthusiasm that can revitalize our communities and enliven our celebrations.”

“Sharing different expressions of faith and devotions offers us a privileged opportunity for experiencing more fully the catholicity of the People of God.”

Pope Francis closed his World Day of Migrants and Refugees message with an appeal to young people to “build the future” together with migrants and refugees.

“We cannot leave to future generations the burden of responsibility for decisions that need to be made now, so that God’s plan for the world may be realized and his Kingdom of justice, fraternity, and peace may come,” he said.