This week, researchers at the US National Ignition Facility in California achieved a major breakthrough in nuclear fusion. For the first time, humans have harnessed the process that powers the stars to generate more energy from a fusion reaction than was used to start it — otherwise known as ‘ignition’. But how close are we to moving this from laboratories to power plants, and will it become the clean, safe, and abundant source of energy the world so desperately needs? Ian Sample speaks to Alain Bécoulet about what’s being called ‘one of the most impressive scientific feats of the 21st century’. Help support our independent journalism at theguardian.com/sciencepod

Invasive non-native species are on the rise around the world and, despite efforts to tackle the issue, their numbers are higher than ever. They have become one of the key driving forces behind biodiversity loss, posing an even greater threat to biodiversity than the climate crisis. Monitoring, tracking and managing invasive species is one of the issues up for discussion at the UN’s biodiversity Cop15, which is now in full swing in Montreal, Canada. Ian Sample gets an update on how Cop15 is progressing from biodiversity and environment reporter Patrick Greenfield, and hears from Prof Helen Roy from the UK Centre for Ecology & Hydrology about why invasive species pose such a serious risk to native wildlife. Help support our independent journalism at theguardian.com/sciencepod

Negotiators from around the world have landed in Montreal, Canada for the UN’s biodiversity conference, Cop15. The summit has been called an “unprecedented” opportunity for turning the tide on nature loss and comes at a critical time: a million species are at risk of extinction and wildlife populations have plunged by an average of 69% between 1970 and 2018. Madeleine Finlay speaks to the director of science at the Royal Botanic Gardens, Kew, Prof Alexandre Antonelli, about the current state of the planet’s biodiversity, what needs to be achieved at Cop15 and how he’s feeling about the possibility of change.. Help support our independent journalism at theguardian.com/sciencepod

The UK Health Security Agency issued a rare alert on Friday, telling parents to look out for signs of strep A infection in their children. Since September, eight children in England and Wales have died after becoming unwell with Group A streptococci bacteria. Typically causing illnesses like skin infections, tonsillitis or scarlet fever, very occasionally strep A can become a life-threatening, invasive disease. But why are we seeing such a steep rise in cases in the UK this year? Madeleine Finlay speaks to Chrissie Jones, associate professor of paediatric infection at the University of Southampton, about the significance of this outbreak and the symptoms to be aware of, and asks Shiranee Sriskandan, professor of infectious diseases at Imperial College London, about how the bacteria can evade our immune systems and whether we may one day have a vaccine.. Help support our independent journalism at theguardian.com/sciencepod

The UK is in the middle of its worst outbreak of bird flu. The current strain of H5N1 avian influenza has devastated wild bird populations, killing thousands and affecting threatened species such as puffins and hen harriers. Bird flu has also been wreaking havoc on poultry, and since 7 November, all captive birds in England have been kept indoors to prevent them catching the virus. How are both wild and captive bird populations coping with the current strain of avian flu? And is the UK prepared to deal with another major animal disease outbreak? Ian Sample speaks with Phoebe Weston, a biodiversity writer for the Guardian, and Paul Wigley, a professor in animal microbial ecosystems at the University of Bristol.. Help support our independent journalism at theguardian.com/sciencepod

At a recent conference in France, scientists and government representatives voted to scrap the leap second by 2035. Leap seconds are added periodically to synchronise atomic time and astronomical time, which get out of sync because of variations in the Earth’s rotation. Madeleine Finlay speaks to JT Janssen, the chief scientist at NPL, the National Physical Laboratory, about the differences between these two times, and what can go wrong when leap seconds are added to our clocks. Help support our independent journalism at theguardian.com/sciencepod

On 15 November the world’s population reached 8 billion, according to the UN. Much of that growth is because we’re living longer. As a species we will continue to age, but eventually stop growing. The UN predicts that in the next century humanity will begin to go into decline. So what happens when societies get older and smaller – a problem some countries are already encountering? Ian Sample speaks to Prof Vegard Skirbekk about how humanity got here, and how we prepare for future demographic change. Help support our independent journalism at theguardian.com/sciencepod

It’s supposed to be the first ever carbon neutral World Cup. Organisers Fifa and host Qatar say they have implemented sustainability initiatives, taken measures to limit carbon output and will offset greenhouse gas emissions by purchasing credits. Fifa has admitted, however, that the tournament’s carbon footprint will bigger than any of its predecessors, and experts believe emissions have been underestimated, calling into question the claim of carbon neutrality. Madeleine Finlay speaks to sports reporter Paul MacInnes about the environmental burden of building stadiums, flying in players and fans from around the world and keeping the pitches green, and asks whether football is really ready to face up to its carbon footprint. Help support our independent journalism at theguardian.com/sciencepod

A year ago at Cop26, global environment editor Jonathan Watts caught up with two climate scientists to hear what they thought about the progress made. A lot has happened in the intervening 12 months, and the world hasn’t stayed on track with its previous promises and pledges. Global carbon dioxide emissions from fossil fuels are expected to increase by 1% in 2022, hitting 37.5 billion tonnes – a record high. Ian Sample called them both up to find out how they’re feeling now. Speaking to Prof Peter Stott, Ian asks whether the 1.5C goal is still alive, and questions Katharine Hayhoe on how she stays hopeful. Help support our independent journalism at theguardian.com/sciencepod

Cop27 got off to a difficult start last week. Attendees struggled with a lack of food and drink, civil society group events were curtailed, and more than 600 fossil fuel lobbyists hit the conference halls – more than the delegations of many of the most vulnerable countries combined. As we head into the second week, Madeleine Finlay hears from biodiversity reporter Patrick Greenfield about what it’s been like in Sharm el-Sheikh, and from environment editor Fiona Harvey about what’s happened so far and whether much progress is likely to be made in the final days of negotiations. Help support our independent journalism at theguardian.com/sciencepod