Soil Health Under Drought, Bird Flu Spillover in Australia, and Artificial Solar Eclipses

Overview

Inside Science explores how extreme heat and drought affect soil below the surface, the emergence of highly pathogenic bird flu in Australia and New Zealand, and the European Space Agency's artificial solar eclipses using Probe 3 formation flying to study the corona. The episode also reports a major archaeological LiDAR discovery in the Amazon that uncovers hundreds of previously unknown earthworks, suggesting a large precolonial population.

Key insights

• Soil health under drought shows how tiny air spaces in soil support microbes and worms, while cracking can cause subsidence and flood risks.
• Bird flu spread through migratory and resident birds raises concerns about cross-species spillover and the role of reassortment in host adaptation.
• Artificial solar eclipses created by Proba 3 enable frequent corona observations far beyond natural eclipses.
• Amazon LiDAR reveals about 400 new earthworks, implying a sizable ancient population and rich regional history.
• Practical safety tips for observing solar events are discussed.

Soil health under drought

The podcast begins by situating listeners in the current drought across Europe and the UK. It emphasizes that soil is a living, breathing system populated by billions of microorganisms, fungi, and worms. In a single teaspoon of soil there can be extensive fungal networks and vast microbial diversity. The host explains that soil is not just solid matter but also contains air-filled pore spaces that are crucial for microbial respiration, water access, and root growth. Under prolonged heat and drought, water in these pores evaporates, especially in clay soils, causing the soil to crack deeply. These cracks can extend up to a meter and lead to subsidence that affects railways, roads, and homes. The discussion moves to how drought harms soil biology: fungi may enter dormancy and spores can wait for better conditions, while nutrient-processing microbes slow or stop, altering nutrient and carbon cycling and impacting plant health downstream. Worms respond by burrowing deeper, secreting protective mucus when dry, but prolonged drought reduces their activity and soil turnover, which is essential for maintaining soil structure and aeration.

The episode then considers legacy effects: when soils are wetted again, microbial communities are different, potentially altering drought resilience and nutrient availability for plants. Researchers are actively studying how to enhance soil resilience, but many processes remain poorly understood, likening some soil biology to a black box. The conversation underlines the importance of soil health for ecosystem function and agricultural productivity, and highlights ongoing research into soil management strategies.

Bird flu spillover in Australia and New Zealand

The program then shifts to wildlife disease with Lizzie Kuyken’s overview of highly pathogenic H5N1 bird flu reaching Australia and then New Zealand. The virus had previously circulated in southern oceans and was detected in migratory brown skuas and giant petrels. The spread to greater crested terns and a swamp in New Zealand indicates spillover from migratory species to resident birds, a key step in establishing the virus in new regions. The hosts differ in their susceptibility and in their viruses’ genetic compatibility; reassortment events can enable the virus to switch hosts and become highly pathogenic in new lineages. The discussion highlights how reassortment, not just mutation, drives the adaptation process that can lead to widespread mortality among birds and potentially affect mammals and humans.

Measures to control the spread include wildlife surveillance and vaccination in some cases, alongside ongoing monitoring of new introductions and host range. The episode notes that while avian influenza has caused human fatalities, sustained human-to-human transmission remains rare, though the risk increases as the virus expands its geographic range and opportunities for reassortment multiply. The host stresses the need for preparedness and continued research into vaccines and surveillance strategies.

Artificial solar eclipses and corona science

The podcast then moves to space science with Ester Bastida Bertageth from the European Space Agency, discussing the Probe 3 artificial eclipse mission. The mission uses two spacecraft in close formation flying to occult the Sun with an occulting disk, allowing the coronagraph instrument to study the solar corona. The occulting disk blocks the bright solar disk, revealing the faint corona where coronal mass ejections and solar wind originate. The two spacecraft are separated by roughly 150 meters in space, a remarkable feat of formation flying with submillimeter precision. Since December 2024, the mission has generated dozens of artificial eclipses, offering extended observational time that would be impractical with natural eclipses. The corona’s dynamic nature means continuous, high-cadence observations are essential to understanding its structure and behavior.

Esteban Bastida emphasizes that observing the corona is vital because it hosts processes that influence space weather, including effects on satellites, GPS accuracy, and power grids on Earth. The interview explains how the coronagraph and occulting disk work together and describes the extraordinary precision required to keep the two spacecraft aligned. The episode notes that the longest artificial eclipse next week could last around two minutes, and the mission has already accumulated hundreds of hours of corona observations since launch.

Amazon geoglyphs revealed by LiDAR

Another major story in the episode concerns a Nature paper describing 400 previously unknown earthworks in the Amazon, identified using LiDAR from a plane. These geoglyphs, ranging from squares to circles and symbols, date from 600 BCE to 850 CE and are hundreds of meters across. The researchers estimate that maintaining and building such structures would have supported a population in the range of 1.5 to 3 million people during a time when the world population was far smaller. The discovery suggests a complex, dense society with sophisticated organizational capabilities that are not well understood, highlighting how LiDAR can uncover hidden aspects of precolonial history beneath dense forest canopies.

Observations, safety, and wrap-up

Throughout the discussion, the podcast avoids sensationalism and emphasizes the importance of careful observation, measurement, and interpretation across disparate scientific fields. The episode closes by highlighting the value of integrating soil science, wildlife health, space physics, and archaeology to understand Earth and beyond. The program ends with a reminder of safety considerations when observing solar phenomena and a nod to the broader scientific community’s ongoing work in these areas.