This is a podcast from the archives of the BBC Reith Lectures.

This lecture in the series Wilderness and Plenty, given by Sir Frank Fraser Darling,

was originally broadcast in 1969.

There are processes going on in the world that are not obvious to many of us,

but that have great importance, and sooner or later we'll have to decide which way we're going.

Last time I spoke of the enveloping character of advanced technology and the choking side effects of pollution.

There's another aspect of this, especially affecting large bodies of fresh water,

such as the great lakes of North America, one at least of the Swiss lakes,

even the new Lake Carreber in Africa,

and perhaps surprisingly, our own Lochleven in Scotland.

Lake Erie is now looked upon as the classical world example of the phenomenon of utrophication,

a sort of pathological overfeeding. Sewers and wastes went into the lake for years,

which meant an excess of some plant nutrients, some animal poisons, and an upset in the natural oxygenation of the water.

Fish life has gone. There's been a dense blooming of algae, microscopic waterweeds, in the summer,

and of course people don't bathe in this great lake anymore.

There's been a further dumping of phosphates into the lake

since detergents were used

and a vast quantity of nitrates

coming from the use of nitrogenous fertilizers

on agricultural land.

Lake Erie is one of those ultimates I've mentioned before

that we should concentrate on as examples of what

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