eric: martin sorg says speculation is not his department. ested we drive across the border to the dutch city of nijmegen. ♪♪♪ eric: for some years, researchers at radboud university had also been noticing a big drop in wildlife numbers. the krefeld study confirmed their worst fears. hans de kroon: all of a sudden we had a percentage, a scientifically proven percentage of how much this whole bulk of insects was going down. eric: i mean, how concerned should we be about that? eric: ecologist hans des kroon has little doubt that farming is responsible. hans: you know, agriculture can have effects on the living conditions in the nature reserves. and we know, for example, that very low levels of insecticides can already disrupt insect life, and you know, these traces have been found spreading around. eric: since world war ii, pesticides have been used to kill organisms that are bad for crops, like cockroaches and grasshoppers, but what if their overuse is now threatening insects that are good for crops, like bees? farmers need pollinators to grow