ROME — Pope Francis on Saturday called for concrete action to combat the “emergency” of plastics littering seas and oceans, lamenting the lack of effective regulation to protect the world’s waters.

Building on his papacy’s concern for the environment, Francis issued a message aimed at galvanizing Christians and others to commit to saving what he hails as the “impressive and marvelous,” God-given gift of the “great waters and all they contain.”

“Sadly, all too often many efforts fail due to the lack of effective regulation and means of control, particularly with regard to the protection of marine areas beyond national confines,” the pope wrote.

“We cannot allow our seas and oceans to be littered by endless fields of floating plastic,” Francis said. “Here, too, our active commitment is needed to confront this emergency.”

Francis recommended a two-pronged approach, saying: “We need to pray as if everything depended on God’s providence and work as if everything depended on us.”

He also denounced as “unacceptable” the privatization of water resources at the expense of the “human right to have access to this good.”

With countries from Italy to Australia promoting policies to thwart migrants from arriving by sea, Francis prayed that “waters may not be a sign of separation of peoples, but of encounter for the human community.”

“Let us pray that those who risk their lives at sea in search of a better future may be kept safe,” Francis added.

Malta and Italy have recently cracked down on charity-run boats which aim to rescue migrants from smugglers’ unseaworthy boats. Other European Union nations, such as Hungary and Poland, have refused to share the burden of caring for some of the hundreds of thousands of asylum-seekers who reached the continent’s southern shores in recent years.

Francis didn’t single out any countries. Instead, he directed part of his message to all politicians having to tackle migration and climate change, appealing for them to apply “generous and farsighted responsibility.”