The sight the whale-watchers have been waiting for finally arrives. Suddenly, the great creature soars up from beneath the waves. Then it turns a somersault and crashes back down again. With a flourish of its tail, it is gone.

Whales are famous for their enormous size. Now their key role in the environment is being recognised too.

"Whale poo is like environmental gold dust," Anjana Ahuja writes in the Financial Times. It is rich in iron, phosphorus and nitrogen, which help phytoplankton grow. These are the algae at the bottom of the sea's food chain.

Phytoplankton produces over half the planet's oxygen. It absorbs four times as much CO2Carbon dioxide. as the Amazon rainforest. So two economists, Connel Fullenkamp and Ralph Chami, are trying to get people to invest in whales.

It is a difficult business. First of all, you need to find the value of a whale.

This means working out how much carbon is absorbed by the phytoplankton which the whale nourishes. Then you have to work out how much CO2 is absorbed by the whale itself. This remains locked in its body for centuries after it has died and sunk to the ocean floor. 

Fullenkamp and Chami believe that the value of the average whale comes to between $2.5m (£2m) and $3m (£2.4m). This assumes that it lives for 60 years.

Their system also needs to be able to track individual whales across the world.

If all goes well, the profits will be used to restore the world's whale population to what it once was. Before large-scale hunting began there were between four and five million.

Yes: Nothing makes things happen more effectively than eager investors, and if Fullenkamp and Chami's scheme works it could transform the environmental movement, with capitalismA form of economy characterised by private property and competition between companies. as a force for good.   

No: The scheme is too complicated and unusual to attract investors, who like tangibleEasily perceptible or real. Tangible changes can be seen or experienced. assetsUseful or valuable things, or items owned by someone or something. . A whale which roams the world and could die if it becomes stranded is too much of a risk for most.  

Or... The answer may not lie with whales, but it will be a huge step forward if investors can be persuaded that natural resources should be factored into all their decisions and not just taken for granted.

CO2 - Carbon dioxide.

Capitalism - A form of economy characterised by private property and competition between companies.

Tangible - Easily perceptible or real. Tangible changes can be seen or experienced.

Assets - Useful or valuable things, or items owned by someone or something.