Political manoeuvring over immigration is set to stunt academic progress worldwide, governments have been warned.
In the UK, the coalition administration plans to slash the number of students admitted from outside the European Union, although the reduction will focus heavily on those studying courses below degree level.
New limits are also being imposed on visas for skilled foreign workers.
As Times Higher Education went to press, universities were absorbing details of the government's plans set out on 23 November by Theresa May, the home secretary.
She said that the majority of non-EU migrants - as many as two-thirds - are students, and that the UK "cannot reduce net migration significantly without reforming student visas". She said that "nearly half of all students coming from abroad are coming to study courses at below degree level, where abuse is particularly common...Too many students at this level have been coming here with a view to living and working, not studying, and we need to reduce this abuse."
She said the government would now consult on proposals to restrict entry to students at degree level, with "some flexibility" for highly trusted sponsors at lower levels.
Universities have also feared that their competitiveness would be affected by a squeeze on the number of foreign academics working in British universities.
Ms May said the number of visas issued to skilled workers would be cut from 28,000 to 21,700 next year, a reduction of a fifth.
This would be achieved by limiting the number of Tier 1 visas to 1,000 - a reduction of 12,000 - while increasing the number of Tier 2 visas to 20,700.
She said Tier 1 would be reserved for "people with exceptional talents - scientists, academics and artists, who have achieved international recognition or are set to do so".
The limits will be reviewed by the Migration Advisory Committee for 2012-13.
The visa rules were unveiled as two papers outlined the importance of student and academic migration to the development of the global academy.
The first, presented at a conference in Cambridge last week by Emília R. Araújo, lecturer in sociology at the University of Braga in Portugal, argues that the movement of both academics and students is pivotal to the growth of human understanding.
"Mobility of researchers is one of the main forms of making knowledge circulate," she said. "No innovation is possible if people do not move and knowledge does not move."
Her study, Mobility in Research Careers - Internationalisation and Discourses of Displacement, says that universities should "foster and invest" in schemes to promote mobility, including better recruitment processes and integration of foreign researchers.
Meanwhile, a report commissioned by the Higher Education Funding Council for England and the British Council says that study abroad boosts students' chances of success in later life and brings bene-fits to the knowledge economy.
The International Student Mobility Literature Review, published last week, reveals that while 370,000 students from outside the UK study in the country, the outflow of home students is also slowly increasing.
But academics are worried that state policies around the world on access to work and study could undermine attempts to improve mobility and the work of the academy.
"At the moment with the economic crisis, governments are cutting all the funds and routes for mobility," Dr Araújo said.
Although the student-visa cap is aimed at those studying below degree level, it could stem the flow of foreign students progressing to UK universities.
Paul Temple, senior lecturer in higher education management at the Institute of Education, said: "It's extremely worrying at a time when universities are going to be under more financial pressure than has ever been the case."