In episode one of this miniseries from June 2025, Jon explores what’s at stake if we fail to act in time. He hears about the crucial role of the rainforest for South America and the global climate, and asks how cattle ranching came to dominate and destroy huge swathes of the rainforest – pushing it to a dangerous tipping point today

As global leaders and environmental activists descend on Brazil for next week’s Cop30 climate summit, Madeleine Finlay speaks to the Guardian’s global environment editor, Jon Watts, who recently sat down for an exclusive interview with the UN secretary general, António Guterres.

In episode three, all of Tam’s lies come to a head and Stuart uncovers exactly where he was sourcing tea to supply to hotels and shops

In episode two Nicola hears how Tam’s network of Scottish tea growers began to have suspicions about exactly what he was selling and where it came from, and how cutting edge science helped provide some answers

An electronic eye implant half the thickness of a human hair has helped people with incurable sight loss to see again, opening up a potential ‘new era’ in tackling blindness. Madeleine Finlay finds out what this implant means for patients and what the future could hold

Biodiversity reporter Patrick Greenfield tells Madeleine Finlay about a recent trip to the Millennium seed bank. He explains the journey a seed takes from from arrival to cold storage, and how some are already helping to return endangered plant species to the wild

Madeleine Finlay hears from the Guardian’s Patrick Barkham about his daughter Milly’s experience, and from Prof John Aucott, director of the Johns Hopkins Lyme Disease Research Center, and associate professor of medicine at Johns Hopkins University

Madeleine Finlay speaks to Timothy Luke, a senior lecturer in the department of applied psychology at the University of Gothenburg, to find out whether sweating, nervous ticks and reduced eye contact really can alert us to deception, and if not, what can?

Madeleine Finlay talks to our science editor, Ian Sample, and correspondents Nicola Davis and Hannah Devlin about the winners of this year’s prizes in chemistry, physics and physiology or medicine

Ian Sample talks to Kevin Hall, a pioneering researcher on ultra-processed foods, about what he wants us all to understand about diet, exercise and weight loss, and why he left the National Institutes of Health

The Ig Nobel prizes were awarded recently - for science that makes you laugh and then think - and the peace prize was given to a cheeky study testing the link between alcohol and language proficiency. Does a drink really help us to converse more convincingly in another tongue, or does it just give us inflated confidence? To find out, Madeleine Finlay speaks to a member of the winning team, Dr Fritz Renner, a researcher in clinical psychology and psychotherapy at the University of Freiburg in Germany

Madeleine Finlay speaks to science editor Ian Sample to factcheck the statements made and find out what decades of scientific research into autism tells us about its causes and why diagnoses of the condition are on the rise

A trial is under way to find out if a £100 blood test could transform the way that the NHS diagnoses Alzheimer’s disease. Alzheimer’s is the leading cause of dementia and diagnosis is currently costly and time-consuming. To find out how this blood test could benefit patients, Ian Sample talks to Prof Jonathan Schott, who is co-leading the trial. He explains what the test involves and why it could pave the way for exciting new treatments for the devastating disease

The murder of political activist Charlie Kirk has prompted fears about rising levels of political violence in the US after a number of high-profile assassinations and attempted assassinations of political figures in recent years. But how connected are these events and do they signal a rise in public support for this kind of violence? To find out Ian Sample speaks to Sean Westwood, an associate professor in political science at Dartmouth College and director of the Polarization Research Lab. He explains how political violence has evolved and why overestimating the support for such acts can be dangerous

At a recent ceremony for world leaders in Beijing, a hot mic picked up a surprising exchange between Vladimir Putin and Xi Jinping about the possibility of living to 150. Putin suggested the secret might lie in repeated organ transplants. But is this the new frontier of anti-ageing research or a fringe and unproven theory? To find out, science editor Ian Sample speaks to Russian affairs reporter Pjotr Sauer and to John S Tregoning, professor of vaccine immunology at Imperial College London and author of Live Forever: A Curious Scientist’s Guide to Wellness, Ageing and Death

The fertility rate in England and Wales has fallen for the third year in a row – a trend mirrored all over the world, with two-thirds of the global population now living in countries below replacement level. In the second episode of a two-part series, Madeleine Finlay speaks to Dean Spears of the University of Texas at Austin and Dr Jennifer Sciubba of the Population Reference Bureau to ask whether declining birth rates are really something to worry about – and how societies can adapt to a future with fewer children