Biodiversity loss is an ongoing challenge, but some of the language we use to describe it may be on shakier ground than we realize. Are we really living through a “sixth mass extinction”? What does that phrase technically imply, and how well is it supported by the data? And what about climate change: how much species-level extinction can credibly be attributed to warming so far, and how do you attribute causes when multiple threats interact?

To explore these questions, I spoke with John Wiens, an ecologist at the University of Arizona whose work focuses on extinction rates and climate-driven range losses. We discuss what the evidence suggests about acceleration (or the lack thereof) in extinction in recent decades, why documented extinctions have been concentrated on islands and in freshwater systems, and how climate change is expected to reshape extinction risk through mechanisms like heat extremes, shifting range limits, and disease dynamics. The thread running through it all is credibility and ambition: how to communicate urgency without overclaiming, and why a stronger conservation goal is not “avoiding a mass extinction,” but preventing extinctions wherever we still can.

Links to resources

• Future threats to biodiversity and pathways to their prevention - The 2017 Tilman et al. article that John referred to in our discussion
• Unpacking the extinction crisis: rates, patterns and causes of recent extinctions in plants and animals - A 2025 article by John and colleagues

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This episode does not argue against renewable energy—renewables are essential to decarbonization—but it does ask what the transition looks like when you account for materials, extraction, and infrastructure.

The clean energy transition is often framed as a straightforward swap: renewables replace fossil fuels, emissions fall, problem solved. But beneath that story sits a harder set of questions. How material-intensive is a renewables-led grid, really? What happens when you account for the steel, concrete, and critical minerals that make wind, solar, and battery storage possible? And if mining expands dramatically to enable decarbonization, what are the environmental and social trade-offs?

To explore these questions, I spoke with Saleem Ali, a systems scientist and industrial ecologist at the University of Delaware who studies the “materials–energy nexus”—the idea that energy systems are constrained not only by fuels and emissions, but by infrastructure, extraction, and supply chains. We talk about why wind and solar can be surprisingly material-heavy up front, how storage options like pumped hydro compare with large battery farms, why nuclear and biofuels remain part of the conversation, and what a more pragmatic approach looks like when every option carries trade-offs.

Links to Resources

• The fight over minerals for green energy — and a better way forward - Saleem's 2024 TED Talk

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The intersection of science, politics, and environmental discourse is full of puzzles: why has nuance gone missing from the conversation? Why are heterodox or balanced views often sidelined? And how do echo chambers, alarmist rhetoric, and the erosion of trust hinder lasting progress in conservation?

To explore these questions, I spoke with Roger Pielke Jr., a political scientist well-known for his work on contested science in contentious policy areas, from climate and extreme weather to COVID origins and sports governance.

Links to resources

• The Honest Broker - Roger's website and blog, with lots of free content and even more in the paid version.
• What Happened on Deliberation Day? 2007 paper mentioned by Roger in which the researchers found that like-minded deliberation led to stronger, more extreme post-discussion views, while mixed groups became more open and less certain.
• The Rightful Place of Science: Disasters and Climate Change - Book by Roger, emphasizing evidence-based nuance over alarmism.
• Messaging Should Reflect the Nuanced Relationship between Land Change and Zoonotic Disease Risk - BioScience paper that we discussed, on the links between land change and zoonotic spillover risk.

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