I study how environmental factors change the structure and diversity of species communities with knock-on effects on the dynamic stability and ecosystem functioning. I describe the structure of communities by complex food-web topologies (who eats whom) and the average body sizes of all species. I am interested in the responses of these structures to global and local environmental gradients in temperature, stoichiometry and habitat fragmentation. Mathematically, I analyze how these structural responses drive the dynamic stability of populations, communities and ecosystem functions.