Two months after al Qaeda terrorists flew airplanes into the World Trade Center towers in Manhattan on September 11, 2001, analytical chemist John Butler found himself working late nights in his lab, developing DNA assays to identify 911 victims from the tens of thousands of charred human remains recovered at Ground Zero. Thinking back, he still clearly remembers the sense of rising to a national need that was shared by dozens of researchers recruited to the same difficult problem. "People wanted to step up and help the country," he says.

Ten years on, Butler's solitary effort at National Institute of Standards and Technology has grown to a large research group working on the forensics of blended, degraded or soiled DNA, and U.S. expertise developed in the wake of 9/11 has also been exported worldwide, put to use identifying victims of mass atrocities in Africa, Asia, Bosnia and Iraq.

It is just one example of how a research direction blossomed as a result of 9/11. Scientists and science policy experts say the federal government's response to terrorist events in 2001, both the September attacks and the anthrax letters in October, have had a profound effect on U.S. research in areas as diverse as forensics, biodefense, infectious diseases, public health, cyber security, geology and infrastructure, energy, and nuclear weapons. Even the social sciences have been affected by the emergence of "terrorism studies" and the new emphasis on the threat in the field of risk analysis.

A major conduit for the shifts is the availability of money: The U.S. Department of Homeland Security (DHS), created by consolidating 22 federal services and agencies in 2002 in direct response to September 11, had a science budget that peaked at $1.3 billion in 2006 before falling again to about $700 million in 2011. Key science-funding agencies including the National Science Foundation, the National Institutes of Health and the U.S. Department of Energy, also put money into research motivated by security concerns (amounting to a total homeland security (this number does not refer to DHS but to homeland security funding across all agencies) research budget of $7.3 billion in 2011) and a small amount of the U.S. Department of Defense money associated with wars in Afghanistan and Iraq ended up in the hands of researchers as well—for example, by funding work on explosives detection and weaponry.

In biodefense, so much money poured into science that Judith Reppy, a science and technology studies expert at Cornell University, even considered whether (adapting the term coined by President Dwight Eisenhower in 1961) a "biomedical-military-industrial complex" has emerged in which scientists, the military and lobbyists conspire to try to keep the funds coming. She rejected that hypothesis, finding that biomedical science in the U.S. remains primarily a civilian endeavor, but says 9/11 has introduced trimmings of "guards, guns and gates," and increased funding research on pathogens that might be used by terrorists.

Some of the post-9/11 changes have entailed increased regulation. Jerry Jaax, a veterinarian and infectious disease researcher who oversees research compliance at Kansas State University in Manhattan, Kans., says that many biomedical fields have been swamped by such new regulations or increased enforcement of pre-9/11 regulations in a bid to prevent researchers and the materials they handle from becoming security threats. He says federal rules on select agents—pathogens that require special facilities and handling—and on imports and exports of biological samples and materials, have slowed the ability of scientists to do research important to public and agricultural health. "Some say we're regulating away our ability to do this kind of research and I think there's some truth to that," he says.

And, a major difficulty has been immigration. The USA PATRIOT Act of 2001 imposed stringent new visa requirements that restricted scientists and science students from all over the world from entering the U.S. Albert Teich, who has tracked the issue for the American Association for the Advancement of Science where he is director of science and policy programs, says that problem peaked in 2003, but has since improved, especially following lobbying of Congress by scientific societies and advice from the National Academy of Sciences, whose 2009 report "Beyond 'Fortress America'" and 2007 report "Rising above the Gathering Storm" were among those to suggest the rules be eased. But the policies had a lasting impact on the ability of U.S. researchers to collaborate and recruit students, he says.

Teich adds that security concerns have cast a shadow over U.S. science in a number of ways, and points to the erection of a steel security barrier around the perimeter of the previously open campus of the National Institutes of Health in Bethesda, Md. "To me," he says, "that fence is a very dramatic visual impact of 9/11 on science."