The natural rainfall historically has a pH of 6. This slightly acid and ‘natural’ acid rain slowly dissolves mountains. Nature has evolved to maintain a balance of a very slight acid rain caused by ‘natural’ amounts of CO2. But now, humans have upset this balance and caused rain to become much more acid, by orders of magnitude. The increase of CO2 also causes problems directly, on top of all of the other acid pollutants emitted by fossil fuel burning.
via 95% Of All Acid Rain Originates From Human Created Carbon Based CO2, NOX, SO2 Fossil Fuel, Nuclear Fuel Burning, Results In Acid Rain, Acid Oceans; Negatively Affects Soil, Birds, Plants, Trees, Oceans Plus People, CO2 Is An ACID Gas | A Green Road Journal