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Hello, this is 6 Minute English from BBC Learning English. I'm Neil.

And I'm Sam. Here at 6 Minute English, we often discuss the new inventions and ideas

scientists dream up to fight climate change, technologies like geoengineering

which could reduce global warming by reflecting sunlight back into space.

Often these ideas are controversial because scientists disagree over whether the technology is possible

and whether in some cases it could do more harm than good.

In this programme we'll be finding out about a new idea to collect lumps of precious metals

called nodules from the bottom of the ocean.

The idea, known as deep sea mining, could provide the metals like copper, nickel and cobalt

which are needed for the green technology used in electric car batteries and other renewable energy.

But could deep sea mining actually damage delicate ocean ecosystems as well?

We'll be hearing from two experts and learning some new vocabulary soon.

But first I have a question for you, Sam.

Mammals like dolphins and whales represent a tiny amount of all marine biodiversity,

the thousands of animal species living in the sea.

Even all the different types of fish combined make up less than 3% of all living things in the ocean.

So according to recent estimates by UNESCO oceanographers,

how many different marine species have their home in the ocean?

Is it A, 70,000, B, 170,000 or C, 700,000?

I'll guess there are around 170,000 animal species living in the sea.

Okay, Sam, I'll reveal the answer at the end of the programme.

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