What is environmental history and how do environmental historians proceed? In this lecture, I will draw on my own experiments in examining long-term developments in mountain regions. After a general introduction, I will pick out a few examples: How should we interpret different agricultural structures in these regions? What role do environmental factors such as soil, altitude and topography play? Why is urbanisation delayed and reduced compared to the lowlands? Finally, we will try to put this problem-orientated approach into a broader framework and also address political questions. The motto of the lecture comes from Jack Goody: "We need only as much theory as necessary".