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Dr Andrew Gunn might be the first person to look at almost every large area of sand on Earth.
Through December 2025 and January 2026, while the rest of us were enjoying holidays, Andrew was in front of his computer, scrolling through 106,540 grid cell images of Earth taken from satellites.
He created the first digital atlas of Earth’s sand dunes.
Digital dunes
Andrew is a Senior Research Fellow in the School of Earth, Atmosphere and Environment at Monash University.
Developing the atlas and classifying sand dunes was a slow process – roughly 5 quiet weeks in an office where the academic grind had halted for Christmas.
“I wanted a complete and exhaustive dataset, and that didn’t exist in the form that was required,” says Andrew.
“I used software applications that created boxes for me to decide if there was dunes or not and I just scrolled around and manually did it.”
He finished with 7.8% of the Earth’s land classified as dunes.
With access to global satellite data and specialised scientific software, the physical task of classification was simple but required expert judgement.
What a dune remembers
Classifying dunes will enable researchers to understand how the Earth might react to climate change.
Each dune is a record of wind, climate and geology. The rings of a tree tell a story of that tree’s life, while the shape, material and direction of a dune holds the story of how the land carved it.
A dune is a story told by two authors: wind and earth.
Dunes can inhabit climates as varied as a Lancelin beachhead, the Sahara Desert and the Russian permafrost. But there are some places with these ingredients that don’t develop dunes.
Sandwiched between two huge dune fields in the Sahara Desert is a stretch of flat, almost featureless sandy terrain. It seems to have every ingredient it needs, but it’s missing a particular quirk of wind that’s critical for dunes.
Credit: Andrew Gunn/Nature
“Imagine you’re between two surf lifesavers flags and all the sand is coming in across the beach, parallel with the coastline,” says Andrew.
“If the wind is faster on the left-hand side and slower on the right, then there’s more material being taken in than brought out.”
Dunes form where sand arrives faster than it leaves, meaning the flat section in the Sahara may act like a sand highway.
This kind of understanding makes dunes a useful marker for how land will react to climate change, though this kind of prediction requires us to learn much more about the interplay between sand and wind.
“We can understand how deserts expand and contract and where we might expect [present day] farmland to become a dune field 100 or 1,000 years in the future,” says Andrew.
A letter from another planet
Maybe the strangest part of this story is that it took so long to build a complete dune map of Earth when we’ve had a dune map of Mars for nearly two decades.
Having dune maps for both planets makes our knowledge of Mars more useful. If dunes arise from wind and sand, knowing about one of these features helps scientists predict the other.
Dunes can help to predict weather patterns across Mars, in places we haven’t collected other data.
“With remotely sensed data, we may be able to identify what the local climate looks like,” says Andrew.
“If we have dunes that are shaped like crescents, we can say we have a climate that has one predominant wind direction.
“If they are long, linear crests, that could mean the wind direction changes between day and night or over seasons.
“With a good dataset, we can test these ideas.”
If a dune is a story written by the wind and sand, Andrew has handed us all the Earth’s correspondence. The remaining work lies in figuring out how this authorship changes across different dunes.
