[1] Previous employment included the Waitangi Tribunal and as lecturer at Victoria University of Wellington.

The title of her doctoral thesis was Inventing New Zealand: Surveying, science, and the construction of cultural space, 1840s–1890s.

[1] She held the positions of professor of history and Pro Vice-Chancellor (Postgraduate) at the University of Waikato, and Pro Vice-Chancellor of the Faculty of Law, Education, Business and Arts at Charles Darwin University in Australia from 2011 to 2016.

[5][3] In 2006, Byrnes was Fulbright Visiting Professor in New Zealand Studies at Georgetown University, Washington DC.

[5] In 2016 Byrnes was appointed assistant Vice-Chancellor (Research, Academic and Enterprise) at Massey University.