The environmental chapter in the newly ratified Canada-United States-Mexico Agreement (CUSMA) builds on the environmental chapters of its predecessors: the North American Free Trade Agreement and the North American Agreement on Environmental Cooperation between Canada, the United States and Mexico. Although CUSMA contains greater environmental provisions in the form of pollution prevention, the control of toxic substances and illegal fishing, and the conservation of wild flora and fauna, it fails to address climate change, the most critical challenge of our time.