[1] From 2020 to 2022, Mrema was executive secretary of the United Nations Convention on Biological Diversity (CBD);[2][3] she was the first African woman to hold this role.

She then earned a Bachelor of Law from Tanzania's University of Dar es Salaam, followed by a Master of Law degree from Dalhousie University in Halifax, Canada and a Postgraduate Diploma in International Relations and Diplomacy from the Centre of Foreign Relations and Diplomacy in Dar es Salaam, Tanzania.

[5] From 2012, Mrema served as deputy director of the Ecosystems Division at the United Nations Environment Programme (UNEP).

[5] She was then appointed Director of the Law Division at the United Nations Environment Programme (UNEP) in June 2014.

[5] Starting in December 2019, Mrema served as Acting Executive Secretary of the United Nations Convention on Biological Diversity (CBD) Secretariat.