Rishi Sunak has given up Britain’s reputation as a world leader in the fight against the climate crisis and has “set us back” by failing to prioritise the issue in the way his predecessors in No 10 did, the government’s green adviser has warned.

Chris Stark, the outgoing head of the Climate Change Committee (CCC), said that the prime minister had “clearly not” championed the issue following a high-profile speech last year in which he made a significant U-turn on the government’s climate commitments. The criticism comes after Sunak was accused of trying to avoid scrutiny of Britain’s climate policies by failing to appoint a new chair of the CCC.

Sunak announced last autumn that he was moving back the ban on the sale of new petrol and diesel cars by five years, as part of a wider dilution of climate policies. At the time, the Tories were aiming to create a dividing line with Labour after their victory in the Uxbridge byelection, which largely came as a result of their opposition to London’s ultra low emission zone.

“It was presented to the country as a step back from going too fast on this transition,” Stark told the BBC. “In the speech itself, he talked a lot about the need to reappraise lots of the steps that take us to net zero. I think it set us back. I think we have moved from a position where we were really at the forefront, pushing ahead as quickly as we could on something that I believe to be fundamental to the UK economy, fundamentally beneficial to the people living in this country, whether you care about the climate or not.”

Stark said significant progress had been made towards net zero and praised Theresa May and Boris Johnson for their commitment to the target. However, he said Sunak had failed to show the same ambition.

“We are now in a position where we’re actually trying to recover ground,” he said. “The diplomatic impact of that has been immense. It doesn’t matter that there were detailed policies within that speech that you could say were very much in line with net zero. The overall message that other parts of the world took from it is that the UK is less ambitious on climate than it once was, and that is extremely hard to recover.”

A government spokesperson said: “We are the first major economy to halve greenhouse gas emissions since 1990 and have set into law one of the most ambitious 2035 climate change targets of any major economy. But we need to reach our net zero goals in a sustainable way.”

Flower farmer John Huiberts stands next to a flamingo made of thousands of organic pink hyacinths. At the annual BloemenCorso, or flower parade, where decorated floats travel through 26 miles of fields in full bloom, his electric vehicle is a sign of changing times in the Netherlands.

“It makes you proud,” said the co-owner of Huiberts Biologische Bloembollen, who went organic 11 years ago. “They say the chemicals are safe but I don’t know. It took me a few years to have good and healthy bulbs, but it is reassuring not to use them any more.”

Huiberts is among a growing number of Dutch flower farmers rejecting pesticides over concerns about conventional floriculture’s effects on biodiversity and the health of people living nearby.

In the past 10 years, Dutch flower farming grew by a fifth, covering 28,000 hectares of Europe’s second most densely populated country. Almost seven billion bulbs were exported in 2022, mostly tulips and lilies, worth about €1bn (£860m).

A court case this week from residents of a village in Limburg aims to stop one lily bulb grower from planting over health concerns about pesticides. Last year, a surprise ruling banned a grower from using pesticides on a Boterveen lily field, citing “substantial evidence” of “a link between pesticides and serious neurological disorders (such as Parkinson’s, Alzheimer’s and ALS)” – although, on appeal, he was allowed to use four substances.

Jonna Vernes is part of a Boterveen group planning to appeal to the courts to regulate future farming. “It is scary,” she said. “From the beginning, we have been concerned about our health.”

Experts have also raised the alarm, in the wake of courtroom victories against pesticide use in the US and state compensation for winegrowers in France who contracted Parkinson’s disease after using glyphosate – a herbicide recently given another 10-year permit for EU use. A critical report from the Noordelijke Rekenkamer audit office said: “It is unclear whether intensive use of pesticides in growing is safe for people, water and nature.”

Prof Bas Bloem, neurologist at the Radboud University Medical Centre, is leading calls for new European testing protocols. “Parkinson’s is the world’s fastest growing neurological condition and there is widespread consensus that it is to a large extent an environmentally driven disease,” he said. “This includes pesticides, although it’s not restricted to pesticides. Farmers have an increased risk, and so do people living in the vicinity of farmland.”

Although total pesticide use has declined since 2012, consumers still expect flowers to look perfect and export standards are high, said Martin van den Berg, emeritus toxicology professor at Utrecht University. “If we compare flower fields like the lilies, the use of pesticides in general is much more extensive than growing corn, wheat or potatoes.

“The more intensively you use the biocides, the larger the impact on biodiversity. And legislation in the EU asks if the compound is carcinogenic or hazardous to reproduction but the one thing which is definitely insufficient is testing on neuro­developmental effects: these compounds are not tested adequately to tell people at a specific dose you’re not at risk – especially children and the foetus in pregnant women.”

Investigative journalists Ton van der Ham and Vincent Harmsen said that when they researched gaps in regulation, they encountered resistance and hostility. “The current laws are not protecting Dutch citizens: a million people live within 250 metres of a field,” said Van der Ham. “We are not against the farmers: we are not activists, we are journalists.

“You could call it tulip fever … the fever that makes us crazy … because we want to make money.”

Back at the flower parade, chairman Willem Heemskerk was keen to point out that the fair – started to cheer people up in 1947 – is a kind of recycling. “Bulb growers allow us onto their fields to gather the flowers,” he said. “This isn’t extravagant use – it is a waste product, and 100 million people will enjoy it.”

Jaap Bond, chairman of the KAVB Royal General Bulb Growers’ Association, said the sector is experimenting with methods such as weed-seeking robots and smart injection techniques. “There is an enormous challenge when it comes to reducing chemical products,” he said. “Everything that is used is a legal chemical that is strictly controlled. This is an enormous, economically important economic sector, but what is often underestimated is that it is also a symbiosis: bulbs are rotated in the ground with potatoes and onions. The lily is really being framed.”

Prof Bloem, however, believes flowers are a “luxury product” and precaution should be prioritised. “Particularly when it comes to flowers, we should ban these pesticides until we have further evidence to show either that they’re toxic or that they’re safe,” he said.

An underwater experiment to restore coral reefs using a combination of “coral IVF” and recordings of fish noises could offer a “beacon of hope” to scientists who fear the fragile ecosystem is on the brink of collapse.

The experiment – a global collaboration between two teams of scientists who developed their innovative coral-saving techniques independently – has the potential to significantly increase the likelihood that coral will repopulate degraded reefs, they claim.

The first use of the combined techniques, to repair damaged atolls in the Maldives, will be shown on the BBC One TV series Our Changing Planet, co-presented by the naturalist Steve Backshall.Hailed as a potential “gamechanger”, the hope is that the technique could be replicated on a large scale to help preserve and revitalise dying reefs.

“All corals in all ocean basins in the world are under pressure,” said Prof Peter Harrison, a coral ecologist at Southern Cross University in Australia.

“Quite a large number have died in some reef areas. So we’re going to end up with big spaces of new real estate for coral larvae, but very few coral larvae being produced because so many adults have died.”

He has pioneered a form of “coral IVF” that involves capturing millions of spawn from “heat-tolerant” reproductive coral after it floats to the sea surface or, alternatively, surrounding coral that has withstood a bleaching event with a cone-shaped net. The net functions like a huge “coral condom”.

“If you breed from heat-tolerant corals that can survive heat stress in the laboratory, the larvae of those corals also have higher heat tolerance than the larvae of other corals,” said Harrison.

The gametes (reproductive cells) then merge together, fertilise and form coral larvae in floating “nursery” pools, which protect them from predators and prevent them from getting lost at sea. “If we don’t support the process of natural selection by focusing on the survivors, we’re going to lose everything.”

This technique, Harrison added, can produce 100 times more coral colonies than would naturally occur on a reef with the same number of larvae: “And we’re working out ways to get it to about 1,000.”

To attract the larvae to settle on a degraded reef, the scientists are broadcasting recordings of fish noises that were captured near a busy, healthy reef. “We’ve done this and restocked degraded reefs with fish,” said Steve Simpson, professor of marine biology and global change at the University of Bristol.

“Working with Peter is the first time we’ve tried it with corals. It maximises the chance that the coral larvae being released find somewhere to live – somewhere that they will then restore the reef habitat.”

Coral larvae, he has discovered, can detect sound according to the way the hairs on their bodies move, and so can be “tricked” into swimming towards – and settling on – a typically silent, unhealthy reef. “It’s like sowing a field that will become a forest again,” said Simpson.

In the lab, the larvae were particularly attracted to the low-frequency grunts, croaks and rumbling sounds made by territorial fish, which can protect coral growing on the reef. “We have discovered that coral larvae hear their way home as babies, before they then choose where to live for up to 1,000 years,” Simpson said.

“They look very simple, and they don’t have ears or a brain, but coral were probably among the earliest animals cueing into their soundscape and dancing to the beat.”

Time is running out for coral reefs across the planet.Scientists recently announced that the world is experiencing its fourth planet-wide coral bleaching event since 1998, with 54% of reef areas in the global oceans experiencing heat stress high enough to turn its colourful coral white. Australia’s Great Barrier Reef has suffered its worst bleaching on record, with about 73% of the 1,429-mile (2,300km) reef affected.

Backshall initially found the idea of using the soundscape of a busy reef to entice the tiny coral larvae to a denuded area “just bananas”.

“To see that happening – to take these gametes into the sea, play them the sounds of a healthy reef and see them actively start swimming towards it – it is probably as close to a eureka moment as I will ever have,” he said.

He fears, however, that if global temperatures rise by 2.5C or 3C, then “coral reefs are doomed”, regardless of these new techniques: “If we continue business as normal in terms of anthropogenic climate change, I don’t think it’s going to matter what we do.

“Tropical reefs are right on the frontline. But if we can keep our levels of temperature increase across the planet down to 1.5C, then there’s a chance – and then these methods will absolutely be part of a positive future.”

The world is “very gradually” waking up to the enormity of the global climate emergency, Harrison said. In the meantime, he and Simpson are “just trying to buy time for corals”.

“If we can keep enough reefs alive through the next two or three bumpy decades to be able to recover, we’ve then got the reefs for the future, once the climate is under control,” Simpson said.

“People say that coral reefs might be the first ecosystem we could lose, and I like to think that, therefore, they are the first ecosystem we can save. If they’re on the brink, and we can save coral reefs, we can save anything. And they become a beacon of hope.”