TORONTO -- When it comes to cleaning up polluted environments, cost can be a major problem.

Take, for example, excessive algae.

In some bodies of water, an abundance of algae means fish die off and the water itself changes colour.

It has been estimated that it would cost nearly US$20 million for all farms in Ohio that feed Lake Erie to reduce their nutrient pollution – the act that causes the algae population to take off – by 30 per cent.

The benefits of a cleaner lake, meanwhile, would only recoup about half that amount.

However, as CTV News Science and Technology Specialist Dan Riskin explains in this week's Riskin Report, there's something missing from that calculation – and it has major implications for protecting local waterways all over the world.

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