Amazing stuff! Good news!
"... In a new study, they present a surprising new tool: gamma rays. Beneath the surface of the parched forests lies thick, granite-rich bedrock, which gradually breaks down and leaves potassium-40-rich minerals in the surrounding soils. Potassium-40 produces gamma rays as it decays—and over millions of years of weathering, the researchers reasoned that the gamma-ray signal should be stronger where soils were shallow and full of potassium-40. Shallow soils in turn mean that tree roots have less room to stretch out for water during drought.
Gamma-ray measurements of three forested areas spanning 400 to 900 square kilometers overlapped neatly with the [conventional] electrical measurements.
In fact, gamma rays were a better predictor of tree mortality than the go-to explanations of the slope of the land or the proximity of trees to streams. The technique could be applied throughout the globe, since one-third of Earth’s ice-free land boasts similar kinds of bedrock and weathered soils. ..."
"... The method revealed that all die-off spots had soils 12 meters deep or less, which made it harder for tree roots to stretch out and access water. But it was incredibly labor intensive, requiring the team to lay electrodes across the forest floor. ...
Still, some applications have already begun: Mining companies operating in the same Western Australian forests have been flying gamma ray sensors to understand the surface geology, but are now considering how much soil should be restored after their operations cease ..."
"... Using airborne sensors, the research team measured gamma rays produced by the natural decay of potassium-40, a naturally occurring radioactive isotope found in rocks and soils. In the highly weathered landscapes of south-west Western Australia, potassium has largely been leached from the soil over millions of years, meaning stronger potassium signals often indicate that bedrock is closer to the surface. ..."
From the abstract:
"Extreme drought and heat are driving forest die-off globally, yet regional-scale mapping of subsurface water storage capacity, governing forest vulnerability, remains a major challenge.
Here, we demonstrate that airborne gamma-ray spectrometry (GRS) of potassium (40K) decay provides a powerful proxy for subsurface constraints on water availability.
In southwestern Australia, we found that spatial patterns of forest die-off during an extreme 2023–2024 drought-heat event were strongly predicted by surficial 40K concentrations.
While GRS measures the upper ∼30 cm of soil,
plot-scale electrical resistivity tomography suggests that elevated 40K signals shallow granite or gneiss bedrock, to depths reaching several tens of meters due to leaching of mobile elements, remnant bedrock minerals, erosional thinning of regolith and biological nutrient recycling from K-rich saprolite.
Airborne GRS can map forest vulnerability across highly leached landscapes, which cover one-third of Earth's ice-free land surface. This enables targeted adaptive management of forests for future drought-heat intensification."
Scientists use natural radiation to predict which forests are most vulnerable to drought (original news release) "What do bananas and drought-stressed forests have in common? According to new research led by the Department of Biodiversity, Conservation and Attractions (DBCA) in collaboration with Murdoch University, both contain potassium and a tiny amount of naturally occurring radiation that can reveal important clues about the world around us."
Fig. 1 The forests of southwestern Australia occur on highly leached soils and experienced die-off during a record-breaking drought and heat event in 2023–2024.(a), (b)Study region in southwestern Australia; ...
(c) historical (from 1923) and recent 18-month cumulative rainfall ;
(d) 30-day running mean temperatures; and a
(e) global map of strongly leached soils, similar to those in this study, with the potential for gamma rays to signal drought vulnerability.
