Quantification of anthropogenic threats to lakes in a lowland county of central Sweden

An evaluation of the negative effects caused by anthropogenic influence on lake ecosystems was performed, using data from 143 catchments in Uppsala Co unty, Sweden. The study included i) technical encroachments; i.e. construct ion of dams, dikes, etc. as well as effects of drainage of land; ii) pollut ion, i.e. eutrophication, acidification, and contamination by toxic substan ces; iii) introduction of nonnative species; and iv) exploitation of specie s populations. Severe damage was caused mostly by drainage of land followed by pollution by toxic substances and, to a smaller extent, introduction of nonnative species and eutrophication. Most lakes were subject to several t ypes of disturbances, interacting in a complex pattern, which made it diffi cult to link the visible effects to the true causes of the disturbance. Fut ure lake management should include analyses of all disturbances to the lake catchments, taking into account the historical perspective, in order to ba lance the threats/damages, in an analysis of the possibilities for maintain ing biodiversity and sustainability in the ecosystems.