Mary has built and led collaborative and innovative conservation initiatives across five continents. In southern Africa, she conducted fieldwork documenting the environmental and social impacts of mining and built an action coalition of community groups, scientists, aid agencies and mining executives. From Stockholm, she contributed to drafting the United Nations Convention on Climate Change and was a part of a team of European Union scientists writing protocols for integrating scientific findings into decision making. Mary also co-led a World Bank project in Washington that established sustainability round-tables in more than 40 developing countries.

At the City of Toronto, she initiated the roll-out of more than 10 new initiatives, including the Climate Change and Clean Air Action Plan, the Renewable Energy Action Plan and the Green Economic Development Strategy. Mary has held positions at the Metcalf Foundation, the Stockholm Environment Institute, the United Nations and the World Bank, the Earth Council, the City of Toronto and with an international engineering firm. In addition to her work at WWF-Canada, Mary was an advisor to New York City Mayor Michael Bloomberg in his capacity as Chair of the C40 Cities Climate Leadership Group.