The Adirondack Lakes Survey, a large-scale study of lake chemistry and biology that began in the 1980s, proved that there was a consistent relation between acid rain, lake acidity and fish. They found that about a third of the 1,469 lakes they sampled had pHs below 5.6 and that while some of these lakes were naturally acid many others had been acidified by acid rain. The most acid lakes were found in the western part of the park where acid rain was most intense and neutralizing capacity of the soils the lowest. In these lakes the numbers of fish, plant, and invertebrate species were always lower than in unacidified lakes.

Subsequent work, especially several studies that reconstructed the chemical histories of lakes from the types of diatoms found in sediment cores, has confirmed all these conclusions. The best current estimates are that the western Adirondacks have more recently acidified lakes than anywhere in the United States. In the last hundred years the pHs of almost all Adirondack lakes over four acres in size and with current pHs under 6.5 have decreased, and the number of highly acid lakes, with pHs under 5.6 has doubled.