The 91-year-old said it was time to save the “future of humanity” after the young animal was shown lying dead after its mother mistook the plastic toothpick for food in an episode of his BBC series Blue Planet II.
Writing in a Radio Times column, the iconic TV presenter highlighted the eight million tonnes of plastic being dumped into the sea every year, as well as global warming and overfishing.
He also called on Donald Trump to reconsider his threat to withdraw from the Paris Agreement.
The comments come amid concerns more than a million birds and 100,000 sea mammals and turtles die each year from eating plastic waste or getting tangled in it.
“Never before have we been so aware of what we are doing to our planet – and never before have we had such power to do something about it,” he said.
“Surely we have a responsibility to care for the planet on which we live? The future of humanity, and indeed of all life on Earth, now depends on us doing so.
“Plastic is now found everywhere in the ocean, from its surface to its greatest depths.”
Sir David spoke of animals being “strangled” by plastic.
“There are fragments of nets so big they entangle the heads of fish, birds and turtles, and slowly strangle them,” he said.
“Other pieces of plastic are so small that they are mistaken for food and eaten, accumulating in fishes’ stomachs, leaving them undernourished.”
He added: “Our wellbeing is inextricably bound up with the health of the oceans.”
However, he insisted “all is not yet lost” and urged people to reduce the amount of plastic they use in everyday life.
On the US President, the veteran broadcaster said he hoped Mr Trump would change his mind on the Paris Agreement, which aims to respond to the global climate change threat.
He said: “Let us hope that Trump will eventually recognise that the Paris Agreement was not about Pittsburgh, or even Paris, but the entire planet.”
Sky’s Ocean Rescue campaign has been urging people to cut out single-use plastic from their lives in a bid to help save the world’s seas.
Sir David Attenborough has called for action on plastic waste clogging up the world’s oceans after a baby albatross was killed by a toothpick in his latest documentary series.
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