With river pollution more in the news than ever before, and sewage now a hot topic, Helen Czerski and Tom Heap investigate how we can restore the health of our rivers. They talk to the Rivers Trust, which this week released its latest ‘State of our Rivers’ report, and ask whether water quality has got better or worse since the last survey three years ago.

They delve into the history of our water system – from the creation of the Victorian sewer network after the “Great Stink” of 1858, to the 21st century Thames Tideway Tunnel, London’s super-sewer currently under construction. But have we got our whole water system wrong? Tom and Helen ask whether regarding water as a one-way disposal system has partly created the mess our rivers are in today. They also hear about some waterfleas with remarkable powers to suck pollutants out of water.

Produced by Emma Campbell for BBC Audio Bristol in conjunction with the Open University

The world's oceans have absorbed huge quantities of carbon dioxide, protecting us from the worst effects of climate change, but how much longer can they defend us? Join Helen Czerski in New Orleans at the world's biggest conference of marine science to meet the experts working to keep the ocean working for us.

Tom and Helen's guests from the American Geophysical Union conference include Jeremy Werdell of NASA and Jaime Palter of Rhode Island University.

With special thanks to the team at the AGU and David Mann of Loggerhead Instruments.

Produced by Alasdair Cross for BBC Audio Bristol in conjunction with the Open University

Why do politicians have such trouble sticking to their environmental promises? Why are they happy to hug a husky one minute, desperate to ditch the 'green crap' the next?

As Labour ditch their £28bn commitment to green the economy, Tom Heap and Helen Czerski are joined by a panel of insiders to analyse the electoral gains and costs of environmental policies and consider the best strategies to maintain the focus of those in power on the greatest challenge to the planet.

Sophie Howe was the Future Generations Commissioner of Wales, charged with ensuring that government policies did no harm to the unborn citizens of Wales. Her pressure helped put a stop to a new motorway in South Wales and supported the government's virtual moratorium on road-building and 20mph zones in built-up areas. Tara Singh is a public affairs advisor with the PR company, Hill and Knowlton. She was a government advisor at the time that Prime Minister David Cameron cancelled commitments on home insulation and put a stop to new onshore wind farms in England. Professor Colin Davis holds the chair in Cognitive Psychology at Bristol University. He has taken part in Extinction Rebellion protests and has a particular interest in the psychological factors that prevent politicians and the public acting against climate change.

Produced by Alasdair Cross for BBC Audio Bristol in conjunction with the Open University.

Should we celebrate the arrival of new species to the UK or drive them out? Tom Heap and Helen Czerski investigate the role of alien invasive species in the British countryside and beyond.

Produced by Sarah Swadling for BBC Audio Bristol in conjunction with the Open University

From the emotional balm of a walk in the woods to the first wooden skyscrapers, Tom Heap and Helen Czerski ask if we can replace a world of concrete and steel with a wooden utopia. Will the Wood Age be healthier for us and for the planet?

Michael Ramage of Cambridge University explains how the development of Cross-Laminated Timber makes it possible to build pretty much any building with wood while Tim Searchinger of Princeton University argues that turning forests into construction material has a high carbon cost for the planet.

Produced by Alasdair Cross for BBC Audio Wales and West in conjunction with the Open University

Rare Earth is a new weekly podcast and radio show from BBC Radio Four which digs deeper into the biggest issues for our planet. Each week, environmental journalist Tom Heap and physicist Helen Czerski will tackle a major story about our environment and wildlife, work out how we got here and meet the brave and clever people with fresh ideas to help us- and nature- thrive.

Helen and Tom won’t shy away from the big stuff- temperatures rising while wildlife declines- but this won’t be a weekly dose of doom laden predictions and tortured hand-wringing. Rare Earth is here to celebrate the wonder of nature and meet the people determined to keep it wonderful.

In the second episode Tom and Helen ask why we're rubbish at tackling waste. Estimates suggest we could cut up to 15% of greenhouse gas emissions if we just used all the stuff that we make and grow. Fashion houses burn their unworn stock and supermarkets make late changes to their orders from farmers, leaving edible crops to go to waste. It's the one climate change solution that doesn't ask anybody to give up anything, so why can't we put a stop to waste? Tom and Helen are joined by the waste-hunting journalist, Oliver Franklin-Wallis and expert on the bio-geography of landfill, Professor Kate Spencer of Queen Mary's, University of London.

Produced by Emma Campbell for BBC Audio Wales and West in conjunction with the Open University

Rare Earth is a new weekly podcast and radio show from BBC Radio Four which digs deeper into the biggest issues for our planet. Each week, environmental journalist Tom Heap and physicist Helen Czerski will tackle a major story about our environment and wildlife, work out how we got here and meet the brave and clever people with fresh ideas to help us- and nature- thrive.

Helen and Tom won’t shy away from the big stuff- temperatures rising while wildlife declines- but this won’t be a weekly dose of doom laden predictions and tortured hand-wringing. Rare Earth is here to celebrate the wonder of nature and meet the people determined to keep it wonderful.

In the first edition Tom and Helen ask how we can bring nature back from the brink. Should we simply abandon great swathes of countryside and let nature reclaim it on its own terms or must we balance the competing demands on our land and micro-manage species and habitats for the best outcomes? Tom meets the herd of bison helping to re-wild a woodland in Kent and visits the Holkham Estate in Norfolk where the government's Landscape Recovery pilot project is funding the transition of intensive farmland into wetlands and passageways for nature.

They're also joined by Cal Flyn, author of Islands of Abandonment and by Rebecca Wrigley, Chief Executive of Rewilding Britain.

Produced by Alasdair Cross for BBC Audio Bristol in conjunction with the Open University

Journalist Tom Heap and physicist Helen Czerski unpack a burning environmental issue each week, discovering fresh ideas and new ways to approach our relationship with nature.