NUTRIENT-POOR FRESH-WATER WETLANDS

Until the introduction of fertilizers in the 19th century nutrient-poo r conditions prevailed in the larger part of The Netherlands. Freshwat er wetlands consequently were of nutrient-poor nature. During the firs t half of the 20th century many surface waters gradually eutrophied, b ut most waters in the Pleistocene area and even some polders in the Ho locene area kept their nutrient-poor conditions. Only during the last decades virtually all waters became eutrophied or polluted. The main s ources of nutrients are agriculture, precipitation and water from the large rivers.