In addition, Finnish lakes have a low buffering capacity. Small headwater lakes and brooks in upland areas with granite bedrock and overburden are sensitive to acidification. These kinds of waters are located throughout the country.
Acidification affects animal and plant populations of lakes.
Such lakes in southern and central Finland have been estimated to have lost up to 2000 fish populations due to acidification. Fish population monitoring in some moderately acidic lakes showed declining trends for sensitive species such as roach. On the other hand, perch populations have recently succeeded in reproduction in some chronically acidic lakes after several years of no recruitment. In northern Finland, chronic acidification has not been discovered, but systems are sensitive especially to acidic episodes, e.g. during snowmelt. In general, effects on fish stocks have not been found.