The natural environment has shaped all of human history. For millennia, from the first human uses of fire and early agriculture to our new world of power plants, specialized chemicals, and global supply chains, people and nature have been intertwined in myriad complex relationships. Environmental history is the study of these relationships. How have people perceived and shaped nature? How have they adapted to a changing natural world? Environmental history can help students understand the roots of contemporary debates over climate change and farm policy, and also gain insights into the very different ways that people have lived in the past. Yale historians study the environmental history of all geographic regions of the world, using the diverse vantage points of political, economic, social, scientific, demographic, and cultural analysis. Yale undergraduates have written senior essays on wide-ranging topics, including environmental justice activism, the local food movement, suburban sprawl, urban gardening, environmental politics, bio-warfare, national parks and forests, irrigation and rural settlement, and international trade.