Historical pattern of phosphorus loading to Lake Erie watersheds

► P loading to Lake Erie over decades has led to cultural eutrophication. ► We estimated P inputs to 18 Lake Erie watersheds from 1935 to 2007. ► Fertilizer use increased and then declined after the 1970s, while crop exports rose. ► Over time, river P export varies mainly with water discharge. ► River export as a fraction of watershed P inputs appears to have recently increased.