I SUSPECT that, like me, many readers of this column will have been enthralled by the BBC’s latest natural world masterpiece, Blue Planet II.

Its mix of stunning film-work, extraordinary revelations about our aquatic wildlife and, of course, the sheer beauty of the undersea world itself have brought in something in the region of 14 million viewers per show and made it the most-watched television programme of 2017 to date.

There have been hints throughout the series about the damage being done to the oceans by the carelessness and thoughtlessness of mankind and, in the finale, David Attenborough gave us a measured warning about the urgent need for action to redress the balance.

The calm and gentle tone of his words made the message all the more powerful.

Introducing the final episode, Attenborough said: “For years we thought the oceans were so vast and the inhabitants so infinitely numerous that nothing we could do could have an effect upon them. But now we know that was wrong.

“It is now clear our actions are having a significant impact on the world’s oceans. The oceans are under threat now as never before in human history.”

The problems of climate change and over-fishing should be well-known to all. What’s less well understood, it seems, is the impact of plastic on our oceans and their wildlife.

Scientists estimate more than eight million tonnes of it are ending up in our oceans ever year, to the extent that there is now an area of floating junk the size of Europe drifting in the Pacific.

Plastic doesn’t rot; it’s estimated it can last up to 500 years so it continues to accumulate in the seas at an alarming rate.

It can have a devastating effect on wildlife, starving to death creatures from seabirds to whales when their stomachs become clogged with it. And, in some parts of the ocean, there is up to 60 times as much plastic as there is plankton.

More than 100,000 seabirds, turtles and marine mammals die each year as a direct result of ingesting plastic.

“Many people,” David Attenborough told us, “believe the oceans have reached a crisis point.”

But exactly who is dumping all this stuff into the ocean?

The answer, sadly, is all of us. About 80 per cent of it comes from land-based activities such as rubbish dumped in the streets and on beaches as well as large quantities lost in transport to and from landfill sites or blown away into the environment from the dumps themselves.

Amazingly, something like two million tonnes of it is carried into the seas along major rivers around the world.

And then there are microplastics: these tiny pieces of plastic, called microbeads, are added to cosmetic and personal cleansing products such as toothpaste and shower gels which are washed down the drain and end up in the seas because they are too small for water treatment plants to filter them out.

There have been campaigns to stop their use and some governments have banned them but plastic fibres from things like clothing and sanitary products are still creating waterborne pollution.

Yet more plastic gets from land to sea via poorly-managed industrial processes, where some plastic is not disposed of carefully or is lost in production.

There is much to be done on a global scale in persuading big companies to reduce the amount of plastic they sell, particularly as packaging and more pressure can also be put on governments to improve the way they manage waste and the amount of recycling they do.

But it’s clear that we as individuals can play a bigger part than we might at first think, whether we live in a bedsit in Manningham or a mansion in Ilkley.

It’s estimated the average person in the UK disposes of more than 100 kilos of plastic every year.

And, as one Blue Planet interviewee put it: “It’s our rubbish that’s going into the oceans and it’s our problem we have to solve.”

The efforts through big shops and supermarkets to reduce plastic carrier bag usage by charging for previously-free ones has made an impact and shows what ordinary people can do if we try.

If we all stopped dropping litter and leaving our plastic cups and containers on beaches and seafronts we could make another big difference instantly.

Not buying cosmetic products that contain microbeads, choosing clothes with natural fibres instead of synthetic ones and avoiding over-packaged food items in supermarkets when we can will all help.

Another of the programme’s contributors put it like this: “It comes down to us each taking responsibility for the personal choices in our everyday life. That’s all any of us can be expected to do. And it is those everyday choices that add up.”

The last word, though, belongs to David Attenborough: “We are at a unique stage in our history,” he told us. “Never before have we had such an awareness of what we are doing to the planet and never before have we had the power to do something about that.

“Surely we have a responsibility to care for our blue planet? The future of humanity and, indeed, all life on Earth now depends on us.”