Restoring land, unlocking opportunity – DeepHorizon’s view

17 June 2025 — Today, under the United Nations banner “Restore the land. Unlock the opportunities,” the world pauses to highlight how bringing degraded soils back to life can deliver jobs, food security and climate resilience.

1. A worsening global picture

Over three‑quarters of the Earth’s land surface – 77.6 percent – has become permanently drier since 1990, while arid zones have swallowed another 4.3 million km², the latest UNCCD assessment warns. Reversing the trend will demand around one billion US dollars in restoration investment every single day until 2030 – a sobering figure that shows just how pressing the issue has become.

Desertification ruins harvests, accelerates biodiversity loss and forces families to move. Waiting is no longer an option.

2. Europe dries out – and strikes back

Europe is not immune: 95.9 percent of its land area now shows a drying tendency, hitting Mediterranean farming and forest ecosystems hardest. In response, the European Commission launches two concrete measures today.

• A Water Resilience Indicators Report, prepared with UNEP, will strengthen drought readiness.
• A Women Negotiators Programme will nurture female leadership in land‑governance debates ahead of UNCCD COP 17.

Both measures sit neatly alongside the Water Resilience Strategy and the Nature Restoration Regulation, the twin pillars of the European Green Deal.

3. Soil physics in plain language

In the short video “Introduction to Chapter 2 – Hydrodynamics of Porous Media,” Prof Mathieu Javaux (UCLouvain) distils a complex subject into three clear messages:

• The soil‑water retention curve links water availability to soil texture and structure.
• The unsaturated zone and its preferential flow paths dictate how heavy downpours infiltrate – or run off.
• The soil–plant–atmosphere continuum behaves as a single, coupled system, so we must model it as one when we forecast yields under drought.

Put simply, if we want restoration plans to work, we need to keep the science of water in soil centre stage.

4. DeepHorizon – shining a light on the hidden half‑metre

DeepHorizon (Deploying Ecosystemic solutions to improve soil Health and uncOveRing subsoil functIons in the critical ZONe) is a Horizon Europe project running from 2024 to 2028. Twenty partners are working together to uncover what lies beneath the plough layer and why it matters.

• Mapping and characterising forty core sites will reveal the biological, physical and chemical make‑up of European subsoils.
• Modelling key functions – from water holding and carbon storage to nutrient supply – will show where and how the subsoil can help.
• Living labs and one hundred demonstration sites will translate the science into tried‑and‑tested farm practices.
• Decision‑support tools and new health metrics will feed straight into the EU Soil Mission.

By looking below the top 30 centimetres, DeepHorizon pushes the fight against desertification into deeper ground.

5. What society stands to gain

Early DeepHorizon figures suggest that restoring deeper horizons could:

• lift water‑holding capacity in sandy loams by up to 30 percent,
• raise broad‑acre crop yields in semi‑arid regions by roughly 10–15 percent thanks to wetter deep roots,
• add around 0.4 tonnes of carbon per hectare each year to the soil, and
• create thousands of skilled green jobs in restoration, monitoring and advisory work.

6. A practical call to action

1. Bring the subsoil explicitly into national restoration plans and the forthcoming EU Soil Health Law.
2. Reward regenerative techniques – such as deep agroforestry and biological subsoiling with tap‑rooted species – that improve structure below 50 centimetres.
3. Invest in research and digital tools (sensors, digital twins) to predict how soils will respond to longer, harsher droughts.
4. Get involved in the DeepHorizon living labs – researchers, farmers and citizens all have a part to play.

“Restoring the subsoil is the hidden opportunity to tackle desertification and secure Europe’s water future.” — DeepHorizon consortium

The Early Days of Soil Science

Through all of human history, soil has operated quietly as an essential foundation because it provides land for agricultural purposes that drives societal development.

During the nineteenth century, Soil Science established itself as an independent field of study. German chemist Justus von Liebig led the way when he introduced his mineral nutrition theory that taught farmers how plants obtain vital nutrients from the ground. The foundational research by this scientist started a new academic discipline which led experts to investigate soil structures and operational modes.

Laying the Foundations in the 20th Century

As scientific knowledge expanded, so did our understanding of soil. By the 1930s, researchers had refined the concept of Soil Profiles, realizing that soil wasn’t just a uniform mass but a layered system with distinct characteristics.

One of the leading voices in this movement was Curtis Marbut, who defended a classification system based on soil morphology rather than just its origin. This shift allowed scientists to standardize soil studies and apply their findings to agriculture, land management, and beyond (Marbut, 1935).

Discovering the Hidden Depths of Subsoil

For much of the early 20th century, soil studies were largely focused on the topsoil (soil surface)—the layer rich in organic matter and teeming with life.

It wasn’t until mid-century that interest in subsoil, the deeper and less explored layers, began to grow. Scientists started to recognize that subsoil played a crucial role in water retention, nutrient cycling, and plant root stability. As technology advanced, improved drilling and sampling methods allowed for more in-depth exploration. This was a game-changer, revealing that subsoil wasn’t as so dormant as once thought. Even Charles Darwin’s earlier work on earthworm activity hinted at how biological processes could influence deeper soil layers (Darwin, 1881).

Why Subsoil Matters More Than Ever

In recent decades, subsoils have gone from being a scientific afterthought to a key player in climate science and sustainability. One of their most critical functions is carbon storage (today carbon markets are very fashionable). Research has shown that subsoils contain vast amounts of organic carbon, sometimes exceeding that found in topsoil. This makes them a crucial component in efforts to combat climate change by sequestering carbon and reducing atmospheric CO₂ levels (Jenny, 1941).

Beyond carbon storage, subsoils also serve as essential water reservoirs. During dry seasons, plants tap into moisture stored in these deeper layers, making them vital for crop resilience and food security (Kautz, Amelung, & Ewert, 2013). Additionally, subsoils act as natural filters, purifying water as it moves through the ground, ultimately improving groundwater quality.

The Challenges of the 21st Century

As climate change accelerates, the role of subsoil in environmental sustainability is more important than ever. Scientists are now working to integrate subsoil knowledge into climate models, helping predict how soils will respond to changing weather patterns.

Additionally, there is an urgent need to raise awareness among farmers and policymakers about the benefits of subsoil conservation. Sustainable land management practices, such as deep-rooted cover crops and reduced tillage, can enhance subsoil health while improving agricultural productivity (Rumpel & Kögel-Knabner, 2011).

DeepHorizon: Advancing Subsoil Science

This is where the DeepHorizon project comes in. By focusing on the often-overlooked subsoil layers, this initiative is shedding light on their ecological significance and potential for carbon sequestration. DeepHorizon aims to bridge the knowledge gap, ensuring that subsoils are no longer ignored in environmental and agricultural policies. The project’s findings could lead to breakthroughs in sustainable farming, climate mitigation strategies, and soil restoration efforts.

Referencies

Darwin, C. (1881). The Formation of Vegetable Mould through the Action of Worms. London: John Murray.

Jenny, H. (1941). Factors of Soil Formation: A System of Quantitative Pedology. New York: McGraw-Hill.

Kautz, T., Amelung, W., & Ewert, F. (2013). Plant–soil interactions in temperate multi-cropping production systems. Crop and Pasture Science, 64(3), 268-285. ·  Marbut, C. (1935). Soil Survey. USDA Handbook 18, Soil Conservation Service. U.S. Department of Agriculture.

Rumpel, C., & Kögel-Knabner, I. (2011). Deep soil organic matter—a key but poorly understood component of terrestrial C cycle. Plant and Soil, 338(1-2), 143-158.