As nearly 150 global leaders lined up – virtually – to address Wednesday’s UN biodiversity summit, the stakes could not have been higher.

“The house is on fire and we are all locked in, because of a disease that came from our mismanagement of nature.”

This was how Inger Anderson, head of the UN Environment Programme, put it in a briefing the day before the event.

“I think there is a realisation that if we don’t take care of nature, we could end up in dire straits,” she added.

With the world grappling with the public health, social and economic devastation of the Covid-19 pandemic, leaders are under increasing pressure to act on their promises to reverse the decline in the natural world.

Environment Why does this summit matter?

This summit is primarily a high-profile forum for world leaders. Its aim is to “highlight the crisis facing humanity from the degradation of biodiversity, and the urgent need to accelerate action on biodiversity for sustainable development”.

But the point at which genuine commitments will be made – to take action to protect nature – will be at the biodiversity conference in 2021. That conference, postponed because of the pandemic, is where all member countries are expected to adopt a new “biodiversity framework” – essentially a global contract to put nature on a path to recovery by 2030.

But a UN report published just two weeks ago, revealed that none of the 20 biodiversity targets that countries signed up to back in 2011 would be fully met.

Those targets were ambitious, encapsulating every aspect of how our human lives intersect with the natural world.

They ranged from reducing the rate of loss of natural habitats like forests and protecting the most precious landscapes for wildlife, to more fundamentally economic shifts, such as eliminating subsidies for “activities that are harmful”, including intensive, polluting farming and fishing practices.

Xi Jinping, President of China, the host country of the 2021 conference, used his pre-recorded address to stress his country’s commitment to turn the tide on biodiversity.

“We need to find a way for man to live in harmony with nature,” he said.

Mr Xi also stressed the need for economic recovery, saying that green development would “increase the potential for high-quality economic recovery from Covid-19.

“We need to recognise that our solutions are in nature – to achieve a win-win.”

UK Prime Minister Boris Johnson used a pre-recorded address to highlight the plight of the scaly, critically endangered pangolin:

“I don’t believe any of us would choose to bequeath a planet on which such a wonderfully bizarre little creature is as unfamiliar to future generations as dinosaurs and dodos are to us today.

“Yet that is what awaits us if we continue down this road. And that’s not just bad news for the pangolins – it is bad news for all of us.”

But in the wake of the UK government’s recent announcement that it would protect more land for nature, the country’s record on biodiversity loss is under scrutiny.

Prof Kate Jones of University College London (UCL), who studies the interplay between nature and human health, described the “massive historical declines” in biodiversity in the UK as “terrible”.

Environment What is different this time?

Inger Anderson insisted that the the “trillions of dollars being invested in stimulus packages” because of the pandemic, provided an ideal opportunity to invest in sustainable growth. “We surely do not want to go back to our damaging ways,” she said.

Elizabeth Maruma Mrema, executive secretary of the UN Convention on Biological Diversity, a multilateral treaty that aims to conserve species, added: “Businesses, banks, the youth – all are ready to take action. This is our last chance and everybody has a role to play.”

By destroying the natural world, Prof Jones explained, “we are currently degrading our asset. So our financial systems need to change”.

She added: “With climate change, our house is on a cliff and it is going to fall off soon. Biodiversity loss and land use change means that it is also on fire – our current trajectory is not sustainable so we have to do something.

“There is more talk and action now than there ever was before, and I am more hopeful now that I have ever been, but it’s a low bar.”

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A ban on single-use plastic straws, stirrers and cotton buds has come into force in England.

The measure, originally due to start in April, makes it illegal for businesses to sell or supply the items.

People in England use an estimated 4.7 billion plastic straws, 316 million plastic stirrers and 1.8 billion plastic-stemmed cotton buds each year.

Environmental campaigners welcomed the ban but called for a crackdown on further single-use items.

An exemption will allow hospitals, bars and restaurants to provide plastic straws to people with disabilities or medical conditions that require them.

Environment Secretary George Eustice said the government was “firmly committed” to tackling environmental “devastation” caused by single-use plastics.

Campaigners welcomed the move but said the items formed only a “fraction” of the plastic waste littering the environment.

Sion Elis Williams, of Friends of the Earth, said ministers “must also do more to challenge our throwaway culture by forcing a shift away from all single-use materials in favour of reusable alternatives”.

Tatiana Lujan, of environmental law charity ClientEarth said straws, cotton buds and stirrers were “some of the most pointless plastics out there” and the ban on them was “a no-brainer”.

But they remained “a tiny fraction” of single-use plastics, she said, adding that countries such as Ireland and France had “shown far more ambition” with targets on reusable packaging and deposit return schemes.

Mr Eustice said the government was “building plans” for a 5p deposit scheme to encourage recycling of single-use drinks containers.

The Welsh government has said it is also considering a similar ban on plastics.

A number of national restaurant chains ditched plastic straws before the ban was announced.

Human activities are destroying the natural world, leading to the extinction of animal and plant species at an alarming rate. Now, world leaders are promising action to tackle the problem. But will it be enough?

Science What is biodiversity and why does it matter?

Biodiversity is the variety of all living things on Earth, and how they fit together in the web of life, bringing oxygen, water, food and countless other benefits.

Recent reports and studies have produced alarming news about the state of nature.

Last year, an intergovernmental panel of scientists said one million animal and plant species were now threatened with extinction.

And this month, a report found global populations of mammals, birds, fish, amphibians and reptiles plunged by 68%, on average, between 1970 and 2016.

Science Are we living in an age of extinction?

Scientists have warned that we are entering the sixth mass extinction, with whatever we do now likely to define the future of humanity. The other five mass extinctions include the asteroid strike that killed off the dinosaurs and many species in the sea.

“We have no time to wait. Biodiversity loss, nature loss, it is at an unprecedented level in the history of mankind,” says Elizabeth Mrema, the executive secretary of the Convention on Biological Diversity.

“We’re the most dangerous species in global history.”

Humans are pushing other species to extinction through hunting, over-fishing and cutting down forests and grasslands.

We are almost entirely responsible for extinctions of mammals in past decades, according to one recent study.

And predictions suggest a further 550 mammal species will be lost this century, if we continue along our current path.

One of the biggest problems for the species we share the planet with, is the rate at which we’re transforming the natural landscape, through building roads and cities, and taking up more land to grow food.

Off land, we are putting plastic into the oceans and depleting fish stocks.

Assessments suggest 75% of land and 66% of the oceans has been degraded by human activity.

Science How do we get off the path to destruction?

Moving off our current devastating trajectory will require some big changes.

At the United Nations Summit on Biodiversity in New York on 30 September, world leaders are expected to declare their countries’ commitments to nature, and possibly a new way of doing things.

“They are not going to say: ‘We will continue a path of destruction.’ They are going to say: ‘We will get on a path of sustainability’,” says Inger Andersen, the head of the UN Environment Programme (UNEP).

Science What is the plan for the future?

Countries are being urged to put their names to an agreement which would be to biodiversity what the Paris climate accord is to climate change.

This comes under the remit of the Convention on Biological Diversity, an international treaty agreed to at the UN Earth Summit in Brazil in 1992.

The convention has three goals: the conservation of biological diversity; the sustainable use of nature; and the sharing of benefits arising from genetic science.

Countries had until this year to reach the targets set a decade ago, which range from stopping extinction to cutting pollution and preserving forests. Despite some progress, none of the targets were achieved.

World leaders are now being asked to sign up to a pledge to protect 30% of the world by 2030 through a ten-point plan that puts wildlife and the climate at the heart of recovery plans from the pandemic.

They have to promise to address the likes of climate change, deforestation, ecosystem degradation and pollution

Scientists say a huge amount is at stake; but it is still possible to reverse the decline in nature, if words and promises are acted upon.

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With astronomers detecting a potential signature of life in the clouds of Venus, there’s obviously going to be a big push to get some new space missions to the planet.

We don’t know if the phosphine gas recently observed by telescopes is coming from floating microbes or has a simple non-biological origin. Right now, nothing is conclusive. But the only way we’re likely to find out for sure is by taking some scientific instruments there.

The Japanese space agency’s Akatsuki orbiter is the one mission at the planet at present, and it was built long before the phosphine question came up – so it’s not really best-suited to study the issue.

What’s needed are some dedicated investigations. And the first opportunity we’ll probably get to perform these will be with the private Rocket Lab company.

This start-up has been making waves with its small Electron rocket, which launches from the Mahia Peninsula in New Zealand’s North Island.

The company’s CEO, Peter Beck, is fascinated by Venus and has already announced his intention to send a mission there in 2023. He’s funding and constructing it in-house.

Rocket Lab will do it with the Photon “kick-stage” that goes on the top of an Electron.

In Earth orbit, this stage does the final placement of small satellites in the part of the sky they want to operate. But the Photon is extremely capable and could shepherd a probe to another planet, and even carry some sensors of its own.

Beck’s plan is to drop off an atmospheric entry probe at Venus. As this falls through the “air”, it would radio back its observations of Venusian clouds to the Photon, which in turn would relay that data back to Earth.

The entrepreneur’s team is working on a payload mass of 37kg.

“That might not sound a lot, but 37kg can get you an awful lot of instrumentation, especially if you’re now very targeted in what you’re looking for and what you’re trying to measure,” Beck told BBC News.

“Venus hasn’t had a lot of love recently, and I think 2023 is the opportunity to put that right. It’s very hard for governments to move quickly but a private mission can. We can go there for a small amount of money, and we can go there many times and have many goes at it, and iterate the learning.”

It’s true, the big space agencies operate by a different philosophy. They aim for super, high-fidelity science and engineering – but this means their top-notch missions fly infrequently and at high cost. It’s a question of trade-offs.

A Rocket Lab entry probe when it falls through the atmosphere at Venus is not going to spend long in the key zone where phosphine has been detected – between 50km and 60km in altitude. The measurements will be brief.

Ideally, what you need is some sort of long-lived platform, dwelling in the clouds of Venus for weeks or months at a time. Like a balloon. That’s the kind of thing big space agencies do.

“This would allow detailed measurement of cloud,” explains Dr Colin Wilson from Oxford University, UK, who worked on the European Space Agency’s Venus Express probe (2006-2014)

“We proposed such a mission – the European Venus Explorer – to Esa in 2010, unsuccessfully. This year, in a Nasa-run Venus Flagship Mission study, we proposed including a balloon that would explore the cloud layer for two months, with specific instruments designed to detect biological material if present.”

It’s a fantastic idea and follows in the pioneering footsteps of the Soviet Vega balloons at Venus in the 1980s, although they only worked for a couple of days.

The problem is that, even if approved for development, we wouldn’t see a Nasa Venus flagship mission – and its balloon – fly until the 2030s at the earliest. And the more modest mission concepts now before Nasa and Esa for consideration are looking at launch slots no sooner than the back end of this decade. Which brings us back to the Rocket Lab type of approach if we want quicker results.

Prof Jane Greaves from Cardiff University led the team that detected phosphine in the atmosphere at Venus. She hopes scientists can find inventive ways of getting new probes to the planet.

“I think in the fairly near-term, we’d like to send even just a really small probe that maybe some other mission could drop off on the way – you know, something going to the Sun. Perhaps it could drop a tiny ‘lab on a chip’ package through the atmosphere so we can get some new data back.”

Peter Beck’s message is “give me a call. If anybody wants to join the team, come join us. But, you know, the bus is leaving; we’re going!”

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

Madeleine Pape weaved her way patiently through a crowded room in Botswana’s Gaborone Conference Centre.

She was determined to catch up with Caster Semenya, the celebrated – and controversial – South African athlete who had once been Pape’s rival.

The Australian wanted to make amends with the women’s 800m triple world champion and double Olympic gold winner, who was the star of an international conference in the African country in May 2018.

“I finally was able to approach her,” Pape tells the BBC.

“I told Semenya how much I respected her and enjoyed seeing her compete.”

This was not how Pape felt the only other time the two women met, in 2009. Back then, she had thought that Semenya did not even belong on the same track as her.

The Berlin controversy

In August 2009, the Australian was one of the runners who lined up alongside Caster Semenya in an 800m heat at the the World Athletics Championships in Berlin.

It was one of the first times Semenya had ever raced outside Africa, but she was already under intense scrutiny.

At 18, the South African had won a junior tournament earlier that year with a time that was only marginally slower than that of more established 800m competitors, such as the 2004 Olympic Champion Kelly Holmes.

Semenya had also managed to shave seconds off her 800m personal best in the space of only nine months.

But those criticising the runner were not accusing her of using banned substances.

Instead, she was “guilty” of being too fast for a woman. Her gender was being questioned.

In the words of Michael Seme, Semenya’s coach at the time, she “looked like a man”.

Many in the world of athletics had reservations about her participation in the World Championships. Madeleine Pape was among them.

“At that time I did think it was unfair for her to compete against the rest of us,” she recalls.

Even the governing body for athletics (IAAF, now rebranded as World Athletics) had expressed doubts about Semenya’s biological sex during the World Championships – news that it had requested a gender verification test leaked to the world’s media just a few hours before the 800m final.

“It was by far the easier option for me to join the chorus of voices condemning her performance,” Pape adds.

“It was just convenient to go along with what most of my colleagues and coaches were saying.”

Once against the idea of Semenya even stepping on a running track, the Australian is nowadays a vocal supporter of the South African’s fight to compete.

What made her change her mind?

Different tracks

Madeleine Pape didn’t have a good run at all at the World Championships.

She finished next to last among seven runners and failed to qualify for the next round.

Semenya, on the other hand, won the heat and never looked back, winning the gold medal in Berlin by crossing the finish line more than two seconds clear of the other runners in the final race.

It was such an impressive margin of victory that one of the competitors in the final, Italy’s Elisa Cusma, accused Semenya of “being a man”.

Pape’s career would end with an injury in 2010. She then pursued an academic career, with a PhD in Sociology and studies on gender issues in sport.

It is as an academic, rather than as a former athlete, that the 36-year-old Australian mostly comes up in internet searches.

In the classroom, Pape saw what she had never recognised on the track.

Difference of sex development

Semenya, now 29, has hyperandrogenism – a genetic condition that makes her body produce higher levels of testosterone.

Testosterone is a hormone that most women have in much smaller amounts than men, and is associated with stronger performance in sports.

In its artificial form, testosterone is part of the World Anti-Doping Agency’s list of banned substances.

Semenya’s condition results from what is known as difference of sex development (DSD).

People with a DSD do not develop along typical gender lines.

Their hormones, genes, and reproductive organs may share a mix of male and female characteristics.

Many in athletics argue that hyperandrogenism offers Semenya an unfair advantage on the track.

Pape used to be among them.

“My views changed when I went to university and had access not only to different perspectives but also to the science behind the arguments that were used against Semenya,” says the Australian.

Run on the track, fight off it

The results of Semenya’s gender verification tests have never been made public and she continued to compete in international events such as the Olympics.

However, World Athletics last year issued a new ruling that forces Semenya and other athletes with hyperandrogenism to take testosterone-reducing drugs in order to be eligible to compete in women’s events between 400m and a mile (1,609m).

The South African challenged the ruling but has lost an appeal in the Court for Arbitration of Sport.

A further legal challenge in the Swiss Federal Supreme Court was dismissed on 8 September this year.

Semenya refuses to take the drugs, arguing that it could endanger her health and that the ruling denies her and other DSD athletes the right to rely on their natural abilities.

As things stand, the South African will not be allowed to defend her 800m title in the Tokyo Olympics next year unless she accepts the drugs, whose effects will almost certainly slow her down.

The fairness argument

For Pape, the stance of World Athletics is harmful to the sport.

“Their agenda so far has been to look for ways to exclude some women,” she says.

“They are missing the ability to listen to these women and to relate to what they are going through.”

Semenya is not the only high-profile case of DSD in athletics.

In the 2016 Rio Olympics, the 800m silver and bronze medal winners were Burundi’s Francine Niyonsaba and Kenya’s Margaret Wambui, who also have hyperandrogenism.

In a statement issued on 8 September, World Athletics stood by the argument that it was pursuing fairness.

“For the last five years, World Athletics has fought for and defended equal rights and opportunities for all women and girls in our sport today and in the future,” the statement read.

“We therefore welcome today’s decision by the Swiss Federal Tribunal to uphold our DSD regulations as a legitimate and proportionate means of protecting the right of all female athletes to participate in our sport on fair and meaningful terms.”

“She’s an exceptional athlete”

Pape, however, sees it differently.

“The system has stacked the odds against Semenya from the beginning,” Pape says.

If in 2009 the Australian thought her rival had an unfair advantage, her views could not be more different now.

“Semenya is an exceptional athlete. Anyone who has won all those medals has got to have something that sets her apart,” she says.

“I don’t think that it is testosterone.”

Is testosterone really so significant?

The link between testosterone and higher performance is controversial among sport scientists.

Julian Savulescu, a professor in Biomedical Ethics at Oxford University, told the BBC that the science behind World Athletics’ arguments is “inadequate”.

He refers specifically to the 2017 study commissioned by the governing body, which claimed that high testosterone was responsible for as much as 3% improvement in runners’ performances.

“It is a single study, conducted by World Athletics, and the full data have not been released for independent replication,” Savulescu explains.

“Semenya has been singled out above any other athlete. I don’t know why that is.”

Supporters of Semenya have often expressed the view she is the victim of prejudice.

The South African athlete is openly gay, and married to another runner, Violet Raseboya.

In July this year, the couple announced the arrival of a baby girl.

Madeleine Pape thinks Semenya’s fans have a strong point.

She argues that other women athletes who dominate the sport in a more emphatic way than Semenya do not get the same scrutiny. She uses the American swimmer Katie Ledecky, owner of a large collection of medals and world records, as an example.

“Semenya is no more exceptional than Ledecky, but Ledecky’s gender has not been openly questioned,” Pape observes.

“But Semenya is a black South African woman who isn’t straight and acts a bit like a tomboy. She doesn’t conform and expresses her identity in her own ways.”

“So, the problem here clearly doesn’t seem to be based on her performances,” she adds.

Indeed, Semenya has not always crossed the finish line in first place.

The South African failed to win the 800m both in the 2011 World Championships and the 2012 London Olympics – she was only awarded the gold medals retrospectively in 2017, after the original winner, Russia’s Mariya Savinova, was disqualified for doping.

Making peace with the past

In that conference in Botswana, Madeleine Pape was not sure if Semenya would remember the only time they had met.

So, the Australian sociologist carried a picture of them together.

It was a snapshot of that 800m heat in 2009.

In the picture, Pape is running alongside other competitors. Semenya is partially “hidden” behind Ukraine’s Tetiana Petlyuk and Kenya’s Janeth Jepkosgei.

It’s an image that Pape still treasures, but with a much-valued addition: Caster Semenya’s autograph.