Critical load exceedance and damage to fish populations

Abstract

To examine the relationship between the critical load exceedance and the damage to fish, the data for fish damage and water chemistry for 1000 lakes in Norway was used to derive the probability of damage to fish populations as a function of the critical load exceedance. When the critical load is not exceeded there is only a small probability of damage to fish, but as soon as the critical load is exceeded, the probability of fish damage starts to increase. Two other sets of data collected independently have also been used to examine the same relationship, the critical load exceedance map prepared for Norway and the fish damage map prepared on the same basis of the interview method . The two sets of data showed that the exceedance of critical loads and to fish populations coincide geographically. Both approaches show that the critical load exceedance clearly indicate ecosystem changes that can be quantifield. Therefore, prognoses carried out for given reduction scenarios can effectively assess the degree of ecosystem recovery.