Ai Weiwei will build more than 100 fences and installations around New York City this fall for “Good Fences Make Good Neighbors,” one of his most large-scale public art projects to date.

Mr. Ai, who lived in New York during the 1980s, said this work is a reaction to “a retreat from the essential attitude of openness” in American politics.

“When the Berlin Wall fell, there were 11 countries with border fences and walls,” Mr. Ai said. “By 2016, that number had increased to 70. We are witnessing a rise in nationalism, an increase in the closure of borders, and an exclusionary attitude towards migrants and refugees, the victims of war and the casualties of globalization.”