Mardik Leopold works on topics that address impacts of human activities on the North Sea and Wadden Sea environment. Study subjects include: shell fisheries in the North Sea, or foreshore coastal nourishment, effects of noise on porpoises, effects of oil spills on seabirds, T-zero and T-1 studies in North Sea gas exploration and wind farms on seabirds and marine mammals, the identification and evaluation of potential Natura 2000 sites at sea, diet studies of fish- and shellfish-eating seabirds, cetaceans and seals, and estimating bycatch percentages among stranded porpoises. Based on knowledge of ecological aspects of birds, marine mammals and their prey, he is engaged in ecosystem evaluations for the Dutch government and advisory projects on the future implementation of the EU Birds and Habitat Directive, on the Dutch Continental Shelf of the North Sea.