They also affected jobs across the university's Waikato Radiocarbon Dating Lab, Thermophile Research Unit, and biomedical, molecular and cellular biology, ecology and biodiversity, and chemistry and applied physics subjects.
Around eight roles across the Earth Sciences and Environmental Sciences teams - to be merged into one - would also be either disestablished, discontinued, or not extended, although three new ones would be created.
The university told the Herald that the changes were "entirely about making the future of the school more sustainable", and part of a five-year strategy developed with staff input last year.
The New Zealand Association of Scientists (NZAS) has however condemned the move, calling it an "alarming example of the severity of stress in the nation's science sector".
"We worry the scale of these cuts will make it difficult for Waikato Science to be sustainable," NZAS immediate past president Associate Professor Craig Stevens said.
"The cuts to so many senior roles is unusual. It will leave the remaining staff with what will likely be crushing workloads and little mentoring.
"Without a doubt it will reduce the quality of research produced in a department that is well known for its earth, environment, ecology, freshwater and marine research."
Stevens said New Zealand's pandemic response had shown the benefits of a well-functioning science system and a healthy societal respect for evidence, and added the cuts seemed "like a damaging and poorly thought-through initiative from one of our major universities".
TEU organiser Shane Vugler said student numbers at the school had increased by 10 per cent this year.
"The other major issue of concern is that the School of Science brings in nearly $38m in received external research funding - but a very small percentage of that is actually allocated to the [school] budget."
Vugler said the union was negotiating with the university to have some of the affected staff redeployed.
"This is effectively less of a restructure and more of a cost-cutting exercise, and we have the capacity to argue for some individuals, because they are dismissing senior academics and replacing them with junior academics," he said.
"It's not that the job or the work has disappeared."
A university spokesperson said the net changes amounted to a reduction of 5.2 full-time academic staff and 1.2 full-time general staff, given new positions were also being created.
The university was "actively supporting" staff to be redeployed into the new roles.
"We have minimised the roles impacted in the change as much as possible through staff opting to take voluntary redundancy and early retirement," the spokesperson said.
"The change will not mean a loss of subjects or papers offered at early undergraduate levels."
The university described the moves as an "opportunity to shift to a more integrated, student-centred approach" with more full-time roles in teaching, undergraduate support and pastoral care within the school.
"It increases support for students, particularly in their first year when they need it most, so they can stay in science."
The NZAS however saw the changes as a "poor decision" and urged the university to reverse it.
The association also said it highlighted a wider problem with support for science at universities - pointing to a contentious shake-up that's been playing out at Massey University for more than a year.
"The university sector is clearly at a cross-roads due to challenges to its recent financial model with its reliance on overseas students," Stevens said.
"However, our fast growing regions can't afford to gut science capability and reputation, particularly in environmental areas, at a time when top talent wants to live and work in New Zealand, we'll risk being left behind intellectually and economically for decades to come."
