The warning, from one of the country's most prestigious academic bodies, follows the emergence of high quality online courses, particularly for postgraduate students.
Their emergence means international students can secure qualifications without the significant expense of studying abroad.
Scottish universities saw their income from overseas students rise to a record £337 million in 2011/12, accounting for 12% of their total income.
In addition, international students contribute an estimated £441m to the Scottish economy every year.
An increading number of universities are launching Massive Open Online Courses (Moocs) that allow unlimited participation and open access via the web.
A paper on the future of higher education submitted to the Scottish Parliament by the Royal Society of Edinburgh said: "A point to consider is the increase in the availability and quality of fully online postgraduate courses, which removes the need for students physically to move to the location of their chosen institution.
"Along with the success of continental European universities in attracting overseas students to courses delivered in English and the improvement in higher education institutions in the countries from which UK universities attract international students, UK universities should adopt a forward-looking policy on higher education which should take account of these emerging trends."
It warned the changes had implications, financially and culturally.
A spokeswoman for Universities Scotland, which represents university principals, said the wider value of international students to modern international universities was crucial.
She said: "The multicultural and social enrichment that international students bring to the student experience for all students on campus cannot be underestimated.
"Nor can the significant cultural and economic contribution that international students bring to Scotland as a country."
Gordon Maloney, president of student body NUS Scotland, warned universities not to overcharge students for online courses.
He said: "It can't simply be the case that online learning becomes a poor substitute and it should not be used as a way to simply gain financially from students without providing them with wider support and benefits.
"That's particularly the case for international students who are already charged ridiculous amounts in fees."
However, Neil Kemp, a leading international education expert, said the growth of online courses could lead to an expansion in international students rather than a reduction.
He said: "The large number of international students that choose to study in Scotland and the rest of the UK reflects a success story.
"This cannot be taken for granted and it's extremely important to better understand the global context in which all universities need to operate.
"However, my belief is that online courses will open up university courses to even more people and there will always be significant numbers of overseas students who want to travel to a different country to study."
In a separate development, Glasgow University has launched its first Mooc. The course, which covers cancer in the 21st century, is open for registration on FutureLearn, a UK-led platform for delivering free, online courses.
Anyone with an internet connection can sign up for free to course which provides participants with video tutorials, reading materials, group discussions and assignments.