[thedoc (OP)]

Global warming may dominate today’s environmental headlines but not so long ago it was acid rain. This emerged after the growth of industry and although the problem peaked in the late 1970s/early 80s and has largely gone away.  But it has left a legacy in rivers and streams...
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[Bored chemist]

"What is the legacy of acid rain? "
Cheap plasterboard.

[Don_1]

Holes in your umbrella.

[damocles]

The acid rain that caused problems back in the 1970s was largely due to power stations burning coal without scrubbing out the sulfur dioxide. It mostly affected Canada and Northern Europe, and caused international tensions because the SO2 often originated from another country. The effect of acid rain was to kill plants by mobilizing aluminium in the soil. Al is quite insoluble at pH between 4 and 10, but rain was falling typically around pH 3 (One recording in Norway showed rain at pH 1.5!). The aluminium was transformed to a soluble form, which was highly toxic to plants and pond animals. The legacy was very sick forests and a lot of dying trees.

Acid rain of a different form -- nitric acid and related compounds from car exhaust -- was a problem in cities which were prone to photochemical smog events; many street trees were killed (it still is, in many places).

In Tasmania, at a very much earlier time, acid rain from a continuing practice of open air smelting of copper, created a zone of about 25 km radius around Queenstown that was totally laid bare in the middle of a region known for its dense forests. The practice was stopped around the 1960s, and some Queenstown locals have been a little upset from time to time because the lunar landscape was regarded as a tourist attraction. The forest has gradually re-established itself there.

In the last few years tropical acid rain in parts of Indonesia and East Malaysia has become something of a problem in association with deforestation operations and forest fires.