The flow of almost 3,400 students across the Border may reduce significantly following Brexit, according to analysis by UK and Irish higher education authorities.
In the Republic, Trinity College Dublin would be most vulnerable to a reduction in number on the basis that it is the most popular choice for undergraduates resident in the North.
Based on data compiled in 2015/16, there was a flow of 3,395 higher education students across the Border.
A total of 1,200 students from the North attended colleges in the Republic, while 2,195 students from the Republic attended colleges in the North.
Both groups currently benefit from being treated as EU students with heavily subsidised undergraduate fees or charges of €3,000 in the Republic and £3,805 (€4,235) in the North.
The possibility of students being charged international student fees after Brexit could lead to fees jumping dramatically to €20,000 and disrupting student flows.
In the Republic, Trinity has the bulk of undergraduate students from Northern Ireland (33 per cent), followed by UCD (20 per cent), Dundalk IT (13 per cent ), Letterkenny IT (7 per cent).
Most were studying in fields such as business and administrative studies, medicine, historical and philosophical studies and dentistry.
In the North, the most popular destinations for undergraduate students from the Republic were Ulster University (71 per cent) and Queen's University Belfast (27 per cent;).
Medicine
Similarly, most students were enrolled on subjects linked to medicine courses or business and administrative studies.
However, the number of undergraduate students enrolled on business and administrative studies has fallen sharply since 2012.
This has contributed to a 22 per cent decrease in the number undergraduate applications from the Republic to the North between 2012 and 2016.
The report was compiled jointly by the Dublin-based Higher Education Authority and the UK's Department for the Economy.
“Despite the many benefits of cross border student flows, there are challenges coming downstream, not least the planned exit of the UK from the EU,” the report states.
"For instance, Northern Ireland students coming to Republic of Ireland higher education institutions to study may in the future be liable for non-EU fees, which can be considerable.
“This may reduce the flow of students from Northern Ireland to the Republic in the aftermath of the UK exit from the EU. Issues such as this need to be given serious consideration by policy makers both sides of the border.”
In 2016, the Higher Education Authority concluded that a soft border with Northern Ireland was preferable post-Brexit to protect the cross-border flow of staff, students and collaboration.
At present, undergraduate students from the North pay the same fees as those in the Republic - the €3,000 student registration charge - for third level courses.
Non-EU students, however, face costs of between €15,000 and 20,000, while the cost for medicine can rise to between €30,000 and €49,000.
Undergraduate students from the Republic who are studying in North pay an annual tuition fee of stg £3,805 (€4,235) per student at undergraduate level, although it is up to £9,000 for those from Great Britain.
Non-EU students, at present, pay significantly more to access these courses.
