Professor Hyland said this year's enrolments were still in doubt because the students would have to begin their work overseas, which would suit some disciplines but not others.
"We've got 200 international students offshore who've accepted a place in a doctoral programme but haven't yet enrolled. They enrol when they are ready to start.
"If we don't convert the majority of those 200 students into enrolments, then there'll be a real problem for us," she said.
Professor Hyland said a downturn in foreign PhD candidates would have a big impact across the entire university system.
"PhDs are an incredibly important part of our research workforce. They are really the lifeblood of our research effort in the universities.
"If you look at most universities they would have similar numbers of PhD students as they have academics and those PhD students can work 100 per cent of their time on their research," she said.
She said a drop in enrolments would also affect research projects run in collaboration with private bodies and Crown research institutes.
"For us, it's going to have a big impact and nationally it's going to have a big impact on our ability to deliver research for New Zealand," she said.
The Government last year announced that 250 foreign postgraduate students would be allowed into New Zealand.
Hyland said between 25 and 30 of the university's doctoral students were eligible and so far four of the 19 who were able to travel to New Zealand had arrived.
One of those students was Australian Joy Mills, who was accepted as a doctoral candidate in April last year, but could not get into the country until January.
Mills said her linguistics research would use eye-tracking equipment and she would not be able to do that anywhere else in the world because of the pandemic.
"Everywhere else every experiment has to be done on the internet and here I can do experiments on actual people so for something like eye-tracking that's really critical," she said.
The president of the Association of Scientists, Troy Baisden, said many foreign PhD students were stuck overseas and they and their supervisors were spending a lot of time trying to work through a complex visa system.
"There has been a special effort to admit some students into New Zealand and give them waivers to get through MIQ. The problem is there's just not enough getting through."
He said some students' initial one-year visas had expired and they needed to reapply. In some cases students had received a place in MIQ, but they no longer had a valid study visa.
"There is a serious net effect," he said.
"Everybody is aware of the problem and struggling with it."
He said the lack of foreign PhD students was harming some big multimillion-dollar research projects.
"Where those students have part of a large project that's holding the whole project back."
Timely to review research funding, organisation
Baisden said New Zealand might have become too dependent on foreign PhD students as a low-cost alternative to higher-paid researchers and it was a good time to reassess how research was funded and organised.
He said stipends paid to PhD students were too low which discouraged many New Zealanders from enrolling in doctoral study.
"Few PhD students today are paid over $30,000 and most are in the 20s. That is tax-free, but still ..." he said.
"They actually earn arguably less than minimum wage or less than the living wage doing what they do and they now carry a lot of the weight of the research that happens in New Zealand."
Baisden said he personally had one PhD student stuck overseas and many of his colleagues had more than one student overseas.
