McTavish said climate change was also an important issue she wanted to address.
Chairman Doug Leeder said it was a pleasure to see the successful appointment coming from within the organisation.
"Fiona will bring to the role key strengths in policy and planning, strategic leadership and experience, not only in the regional sector, but also from previous executive positions held in both the education and health sectors," Leeder said.
"I would also like to acknowledge the contribution that Mary-Anne Macleod has made to the council and the organisation over the past 11 years, seven of those as the chief executive.
"Mary-Anne has developed and implemented major policy and science advances, complex financing and accountability structures, and made a significant contribution to local government at a national level. She has also led the organisation through several major crises, including the Rena grounding and the Edgecumbe floods.
"We wish her well in her future endeavours, in whatever role or function she wishes to pursue," Leeder said.