Martha Pollack is the president of Cornell University. The views expressed in this commentary are her own. View more opinion articles on CNN.

(CNN) When I became president of Cornell University, I inherited leadership of one of the great institutions of American higher education.

Cornell was founded on a principle both simple and revolutionary: We are "an institution where any person can find instruction in any study." Not every person -- an impossibility on any campus bound by finite resources -- but any person, no matter their race, gender, religion, or nationality.

That idea, articulated so clearly over a century and a half ago, mirrors in its ambition the early philosophy of our nation: When the door is open to all, we all thrive.

As the national debate over immigration swirls on, we are at risk of losing sight of that foundational ideal. On America's campuses, a tightening net of government regulations is increasingly excluding some of the young minds our country needs most -- a trend that endangers our ability as a nation to innovate and compete.

Across the country, according to the Institute of International Education, over one million international undergraduate and graduate students make essential contributions to research, to technology development, and to our ability to educate the next generation of citizens for a complex world. They also contribute nearly $39 billion to the United States economy, creating or supporting over 455,000 jobs.

All of that is at risk when these students are barred from entry, prevented from remaining, or sufficiently intimidated by our system of immigration that they choose to stay away.

A growing body of evidence suggests that this is exactly the situation we now face. In early February, the Council of Graduate Schools released a study showing a 4% decrease in international graduate applications over the past year, following a 3% decrease the year before . Late last year, the Institute for International Education reported a 6.6% decline in new enrollment of international students -- the first such decline in a decade

For those who work with and teach these students, the causes of this trend -- and its costs -- are painfully clear. The process for obtaining or extending a student visa, always cumbersome, is now unpredictable and fraught with risk

In August, US Citizenship and Immigration Services revised its "unlawful presence" policy, opening students to the real possibility of being deported and barred from reentry for administrative infractions such as inadvertently working one hour too many at an on-campus job, missing a piece of mail or even because of long processing times for correctly submitted applications.

The Trump administration has either suggested, or placed on its regulatory agenda, a host of new proposals making existing visa procedures even more onerous: reducing the length of visas, requiring students to reapply annually or limiting every student's stay in the United States.

National security is the concern most commonly cited for these procedural and policy changes. Yet most research universities, including Cornell , conduct no classified research; those that do must meet strict standards and controls

Legitimate concerns over information security and intellectual property rights must be addressed through appropriate institutional policies and procedures, and, in fact, the government requires that all institutions receiving federal research money have these in place . Barring international students, by contrast, is a response of dubious effectiveness and certain harm.

The students our nation rebuffs don't, in general, give up on their educations: they take their talents elsewhere. According to a study in the Journal of Studies in International Education, the number of international students studying in China has jumped tenfold since 1995, for example , while India has set a goal to quadruple its numbers by 2023. If America does not see the value of bringing the world's best young minds to its universities, other countries do.

Research universities, as part of their purpose and identity, are places of openness. The research that happens here is publicly presented and published. Does some of that knowledge make its way back to other countries? Do the skills and connections of our international students fuel the progress of other countries, some of which are our competitors? They certainly do -- just as the work of students and scholars from abroad fuels ours.

When we discourage or turn away international students, we lose much more than the students themselves. We lose people like Cornell alumni Sanjay Ghemawat, who created much of the infrastructure that powers Google, and Pablo Borquez Schwarzbeck, whose LA-based company Produce Pay helps farmers better monetize their crops

We lose their inventions and innovation, their collaborative input and their contributions to our communities. In time, we will lose our centers of technical excellence, which will, inevitably, migrate to places where every talented contributor is welcome. Ultimately, we will lose not just our status as a global leader, but the very identity that earned it.

Stay up to date... Sign up for our new newsletter. Join us on Twitter and Facebook

The nation's doors, like those of Cornell, cannot stand open to every person. But we must find a way to keep them open to "any person" -- open not just a begrudging crack but wide in welcome.

This article has been corrected to clarify that Institute for International Education data has shown a decline in enrollment of new international students.