Sir David Attenborough at the Great Barrier Reef. A major section of the program is devoted to the Great Barrier Reef, where filming began in 2016 on Lizard Island. The program charted the Great Barrier Reef's worst-ever bleaching event, caused by a combination of a warming ocean and an El Nino, which turned healthy corals into white rubble. The following summer brought another big bleaching event, centred more to the south, leaving about half the reef affected during the two bouts. Attenborough said more than two-thirds of the world's coral reefs had suffered from rises in ocean temperatures over the last three years.

Aerial surveys by the Australian Research Council's Centre of Excellence for Coral Reef Studies has revealed only the southern third of the Great Barrier Reef has escaped unscathed from coral bleaching. Credit:AAP "Coral reefs could be gone by the end of this century," Chris Langdon, professor of Marine Biology and Ecology at the University of Miami's Rosenstiel School of Marine and Atmospheric Science, told Attenborough. "And the cause of this? Carbon dioxide. The more carbon dioxide in the atmosphere, the more acidic the ocean becomes," said Attenborough, raising the twin threat - acidification, along with warmer oceans - that is being triggered by changing the chemistry of the atmosphere. Healthy coral at the southern end of the Great Barrier Reef. Credit:Tory Chase "Evidence points to the burning of fossil fuels as the primary cause for these increasing levels of carbon dioxide.

"And this is man-made beyond question?" Attenborough asked Langdon. Dwarf minke whales on the Great Barrier Reef. Credit:Dean Miller "Beyond question," replied Langdon. But he said the death of the reefs could be averted by switching from fossil fuels to renewable energy sources like solar and wind. The coalition, under both Malcolm Turnbull and his predecessor Tony Abbott, have launched ideological attacks on the former Labor government's marine parks plan and renewable energy target. It has scaled back the 2020 renewable energy target and is preparing to reduce the area of Australia's marine parks by almost half. Some 1,200 scientists have called on the government to reconsider, saying the cuts to the parks are a "retrograde step."

Attenborough said the creation of more marine parks, which currently cover just one per cent of the ocean, were "vital" to protecting reefs from dying. Yet despite the dire scenes depicted in his documentary, Attenborough remained hopeful. "We can turn things around, we've done so once before," he said. Attenborough cited the 1986 agreement to end commercial whaling, which he said had been instrumental in the recovery of whale species, despite some countries – such as Japan – continuing to hunt the creatures. Plastic pollution entering dolphin tissue

Attenborough devoted much of the program to the eight million tonnes of plastic that ends up in the world's oceans annually. The Blue Planet II team said they found plastic in every single ocean they filmed, "even in the most remote locations". The program showed fish entangled in nets of plastic, a rice packet spewed up by an albatross in Georgia, and another bird killed by a plastic toothpick that had pierced its stomach. "Once in the ocean plastics break down into tiny fragments – micro fragments," said Attenborough. He said these, combined with the industrial chemicals that end up in the ocean, caused a "potentially toxic soup." Small organisms ingested the micro plastics and sent the toxins right through the oceanic food chain, he said.

"Dolphins are at the top of this food and it's now thought that pollutants may be building up in their tissues to such a degree that a mother's contaminated milk could kill her calf," he said. He said scientific autopsies of dolphin calves found dead off the coast of the United States had been performed. Attenborough said the problem "must be tackled for the sake of all life in the ocean." The program also showed how clown fish make noises to protect themselves from predators. Clown fish which become separated from their families, as famously depicted in the Pixar blockbuster animation film Finding Nemo, can use noises to find their way back to their anemones. But those noises can be drowned out by fishing boat engines roaring overhead.

"We're only now beginning to realise what an impact our noise is having on the ocean," said Attenborough. Australia's response Environment Minister Josh Frydenberg defended the coalition's record on the reef and said it was "rightly valued by the Australian and international community as a place of intrinsic beauty and incredible biodiversity." But he did not address the coalition's plan to cut back the marine parks and the amount of renewable energy, instead attacking Labor's management of the reef when they were in power. "After six years of Labor mismanagement, the Great Barrier Reef was on the World Heritage Committee's watch list to be 'in-danger,' with five massive dredge disposal projects in the marine park planned," he said.

"The Coalition took unprecedented action to fix Labor's mess ending all five dredge disposal plans as well as banning all future capital dredge disposal projects in the Great Barrier Reef Marine Park. "We also developed a comprehensive Reef 2050 Long-Term Sustainability Plan setting out our strategy to manage, protect and improve the Reef for future generations." "As a result of the Coalition's actions, the World Heritage Committee removed Australia from the 'in-danger' watch list, and praised Australia as a global role model for reef management. "The Coalition has a comprehensive set of policies to invest in, and protect, the Reef having already invested $461 million in reef funding as part of a broader $2 billion ten-year plan by Australian governments focussed on water quality, reducing run off and eradicating crown-of-thorns starfish." "Just this week we announced a world leading research project which will mix warmer surface water with cooler waters from the deep in an effort to reduce the impacts of thermal stress on the Great Barrier Reef to mitigate coral bleaching events.

"This is on the back of announcement last week of a trial on the Great Barrier to identify highly resilient reefs and pilot 're-seeding' to restore coral." British considering plastic tax Like millions of Britons, the British Environment Secretary Michael Gove is a fan of the series. Gove said he was "haunted" by episode four called Big Blue. He vowed the Conservative government would "work urgently to identify further action." "The imperative to do more to tackle plastic in our oceans is clear," he said. "We must act."

The British government said in its budget statement that it would explore ways to use the tax system to curb the use of single-use plastics like takeaway containers. "The UK led the world on climate change agreements and is a pioneer in protecting marine environments," Chancellor Philip Hammond said. "Now I want us to become a world leader in tackling the scourge of plastic, littering our planet and our oceans." The government has already introduced a 5p (9c) charge for all plastic bags in the UK. Loading Government data shows Britain's seven main retailers have issued 83 per cent – or 6 billion – fewer bags in 2016-17 compared to 2014, prior to the charge.