In brief
The creeping loss of fertile land in dry regions: soil loses its humus, water and life until it can barely carry anything at all.
Learning path: Holding water on the slope
Station 1 of 6
What is desertification?
The word misleads, and that is its most dangerous trait. Desertification does not mean the Sahara wandering and dunes rolling over villages. It means land in dry regions quietly losing its vitality: first the plant cover, then the humus, then the capacity to hold water. The UN convention has defined it since 1994 as land degradation in arid, semi-arid and dry sub-humid areas, caused by climatic variations and human activity. It is a process, not a place, and it runs where hardly anyone is watching: on abandoned fields, overgrazed slopes, depleted soils.
Its engine is a feedback loop. Where vegetation is missing, the sun strikes bare soil and heats it. Hot soil loses water and soil life faster. Rain that can no longer infiltrate shoots off the surface and takes the fertile layer with it. With every turn the site gets harder, and harder sites carry less vegetation. As a rough professional marker: once humus content falls below one percent, the process is under way. The spiral turns downwards long before anything looks like a desert.
For Sardinia this is no distant warning. According to surveys by the research council CNR, 30 to 50 percent of the island's area counts as at risk, and the environmental agency ARPAS officially maps the sensitive zones, using the same European methodology once developed for the Mediterranean in the MEDALUS programme.
How Terra Humana understands it
Terra Humana does not work on desertification, it works inside it. Sa Medada lies in exactly the landscape in question: a slope in the Ogliastra on the eastern side of Sardinia, with five dry months a year, on an island where a large share of the land appears on the risk maps. That changes the project's role. It is not outside help for a faraway problem, but an answer from within, on the spot, at its own risk.
And it grounds the approach: if desertification is a self-reinforcing spiral, then reversal is not a single measure but the art of setting the same spiral turning upwards. Every method Terra Humana deploys is a tooth in that gear: plant cover against the heat, humus against the water loss, pioneers and nurses against the bare beginning.
Sa Medada
What this looks like at Sa Medada
Sa Medada lies in the Ogliastra on the eastern side of Sardinia, with a dry season from May to September. The wetness map from LiDAR data shows a comparatively dry main area and moister channels along the edges. That is why Project Eden begins with pioneer plants, ground cover and holding water, the levers that can turn the downward spiral around.
More about Project EdenFrequently asked
What is desertification?
Desertification is the degradation of land in dry and semi-dry regions through climatic variations and human activity, as the UN Convention to Combat Desertification (UNCCD) has defined it since 1994. The misunderstanding is built into the word: it does not mean the spread of sand deserts, but a process that can run anywhere water is scarce. Soil loses its plant cover, then its humus, then its ability to hold rain, and with each step the land becomes hotter, drier and poorer. What stands at the end is not a sea of dunes but exhausted land that can barely carry anything.
Is Sardinia affected by desertification?
Yes, and it is officially mapped. According to surveys by Italy's national research council CNR, 30 to 50 percent of Sardinia's land area is considered at risk of desertification; for Italy as a whole the figure is around 20 percent, with Sicily most exposed. The Sardinian environmental agency ARPAS maintains its own sensitivity map based on the European MEDALUS methodology, marking the most vulnerable zones, among them Nurra, Anglona and Logudoro in the north, and Campidano, Marmilla, Sulcis-Iglesiente and Sarrabus in the south. The island belongs to the European regions where the question is anything but theoretical.
How do you recognise early desertification?
By signs that look harmless one at a time. The soil's humus content sinks; as a rough professional marker, a content below one percent counts as an alarm value where healthy soil carries several percent. Rain no longer infiltrates but shoots off, tearing soil away with it. The plant cover becomes patchy, bare patches heat up, springs and wells respond later to the winter rains. Each of these signs strengthens the others, and that feedback is what makes the process so treacherous: it accelerates itself long before it looks dramatic.
Can desertification be reversed?
Yes, though not by one grand stroke but plot by plot, with the same levers run backwards. Where plant cover returns, the soil cools and holds the rain. Where humus grows, the land stores water instead of losing it. Where pioneers and nurses make the start, more demanding species follow. The spiral that runs downwards also runs upwards, only more slowly, and only if someone begins. Regreening projects around the world prove it; the honest caveat is that it takes years to decades, and it does not succeed on every site.
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Sources
- UNCCD, United Nations Convention to Combat Desertification (1994)
- CNR, surveys of land at risk of desertification in Italy (presented via ANBI)
- ARPAS, Carta delle aree sensibili alla desertificazione in Sardegna (ESA/MEDALUS, 1:100,000)
- MEDALUS, Mediterranean Desertification and Land Use, EU research programme
Last updated: 2026-10-01