When Steven Chu’s parents came to the United States from China during World War II to attend graduate school at MIT, they found that they could not return to their native country. Fearful that they would be pursued and killed like some of their family members, they instead became U.S. citizens and raised their children—including an eventual Nobel Prize winner—in their new home.

Tumultuous events like China’s Communist revolution, the rise of fascism in Germany and Italy in the 1930s, and the collapse of the Soviet Union in the early 1990s brought “gifts to American science,” Chu said in his presidential plenary address to open the American Association for the Advancement of Science’s Annual Meeting in Seattle.

For decades, “graduate students and postdocs from foreign countries came to study in the United States and stayed because we are a free, open and accepting society,” said Chu, the co-recipient of the 1997 Nobel Prize in Physics and U.S. Secretary of Energy from January 2009 to April 2013.

The benefits to global science have been tremendous, Chu said, noting that 34% of all U.S. Nobel laureates have been immigrants to the United States. Among U.S. Fortune 500 companies, 45% were founded by immigrants or their children, with familiar-sounding names like Jeff Bezos and Elon Musk.

Recent attempts to restrict foreign student visas and efforts to limit collaboration with international scientists could have a chilling effect on future U.S. scientific and economic gains, Chu warned.

U.S. policymakers are now looking at ways to prevent theft of U.S.-funded research and advanced technologies by foreign entities, including the Chinese government. These efforts have led to confusion as scientists and government officials differ on what kinds of data, equipment and expertise-sharing are considered “sensitive” and protected as part of national security, Chu said.

China has increased its R&D spending in the past decade and is pursuing some of the same national goals that Chu proposed as energy secretary, including a surge in clean energy technology. “The U.S. should respond by increasing investment in science, technology and STEM education, not by erecting walls to international collaboration,” Chu said, drawing sustained applause from his audience.

Chu is the William R. Kenan, Jr. professor of physics and professor of molecular & cellular physiology in the Medical School at Stanford University. His plenary address was wide-ranging, touching on topics like the need to speed up the response to global climate change.

Trends in sea level and carbon emissions remain dire, he said, but there are hopeful signs that technology could help address some of the drivers of climate change. He cited improvements in electric vehicle batteries, solar power, the use of microbes to replace chemical fertilizers and a shift away from meat production toward plant-based alternatives that could slow the rate of carbon emissions.

Chu suggested that developing and developed countries will need a new measure of wealth in the face of climate change. “Because as long as the measure of wealth is GDP, you’re going to increase production and consumption of stuff,” he said. “So, think of what you treasure. It should be quality of health, including your health in old age. It should be education, including continued and renewable education, lowering stress levels and connections with families and friends.”

The meeting’s local co-chair, University of Washington President Ana Mari Cauce, and Seema Kumar, vice president of innovation, global health and policy communication at Johnson & Johnson, welcomed AAAS attendees in brief speeches before the plenary address. AAAS Chair Margaret Hamburg presented two major awards: the Philip Hauge Abelson Prize and the Newcomb Cleveland Prize.

[Associated image credit: Robb Cohen Photography & Video]