February 23, 2023

The soil beneath our feet is the world’s largest terrestrial carbon store. Pioneering farmers and agronomists are working on methods to harness its potential. Their insight: Climate protection and a rewarding harvest can go hand in hand.

 

Professor ­Rattan Lal hat 60 Jahre damit verbracht, die Geheimnisse von Böden zu entschlüsseln und Anbaumethoden zur Verbesserung der Bodengesundheit zu entwickeln.

ie Böden der Erde enthalten mehr Kohlenstoff wie die Wälder und die Atmosphäre zusammen“, sagt Professor Rattan Lal. Seit ihren Anfängen vor 10.000 Jahren hat die Landwirtschaft diesen riesigen Kohlenstoffspeicher erschöpft, indem sie Wälder durch Felder ersetzt hat. „Wir sollten daher die Rekarbonisierung des Bodens als wesentlichen Teil der Lösung für den Klimawandel betrachten.“

 

Lal ist Ehrenprofessor für Bodenkunde an der Ohio State University/USA. Er betont, dass die Landwirtschaft naturpositiv werden muss. „Das bedeutet, mit weniger Mitteln mehr zu produzieren. Also einen effizienten Input im Blick zu haben, nicht nur die eingesetzte Menge.“ Zu viele Betriebe seien auf hohe Mengen an Düngemitteln und andere chemische Stoffe angewiesen, um rentable Erträge zu erzielen. Regenerative Verfahren seien verblüffend einfach: die Bodenbearbeitung minimieren, wassersparende Tröpfchen- anstelle von Oberflächenbewässerung sowie bodendeckende Pflanzen und landwirtschaftliche Reststoffe zur Nährstoffanreicherung einsetzen.

 

„Und wir sollten einen geringeren Anteil des Bodens selbst nutzen“, fügt er hinzu. Eine geringere Nachfrage nach landwirtschaftlichen Erzeugnissen durch eine effizientere Nutzung und veränderte Ernährungsgewohnheiten würde es ermöglichen, der Natur mehr Land zurückzugeben und so Milliarden Tonnen Kohlenstoff zu binden. In einigen Teilen der Welt sind bereits groß angelegte Projekte zum Schutz des Bodens im Gange. Im Rahmen des Naturschutzprogramms „Grüne Mauer“ in China entsteht der größte von Menschen geschaffene Wald der Erde. Nach Abschluss in den 2050er-Jahren soll er sich über 4.500 Kilometer erstrecken und das Vordringen der Wüste Gobi nach Süden verlangsamen. Die meisten Regionen verfügen jedoch nicht über die erforderlichen politischen, gesellschaftlichen oder wirtschaftlichen Strukturen, um solch weitreichende Änderungen der Landnutzung voranzutreiben. Die Gesundheit ihrer Böden hängt von Entscheidungen Millionen einzelner Landwirte ab. Das könnte der beste Ansatz für die nächste grüne Revolution sein.

The soils of the world contain more carbon than its forests, woodlands and atmosphere combined,” says Professor Rattan Lal. Agriculture, by replacing forests with fields, has been depleting that vast carbon store since its birth 10,000 years ago, so “we should see recarbonization of the soil as an essential part of the solution to climate change.”

 

Lal, Distinguished Professor of Soil Science at Ohio State University, United States, stresses that agriculture must become nature-positive. “That means producing more from less: focusing on the efficiency of inputs, rather than the rate.” Too many agricultural systems, he explains, rely on very high volumes of fertilizers and other chemical inputs to achieve their current yields. The ­alternative regenerative agriculture techniques he espouses are deceptively simple: ­minimizing tillage, replacing flood irrigation with more water-efficient drip approaches, and using cover crops and agricultural residues to boost nutrients. 

Professor Rattan Lal taking soil measurements in a field.

Professor Rattan Lal has spent 60 years unlocking the secrets of soils and devising farming methods that can improve them.

“And we should use less of the land itself,” he adds. Reducing demand for agricultural products through more efficient utilization and dietary changes would allow more land to be returned to nature, capturing billions of tons of carbon.

 

In some parts of the world, large-scale efforts to protect the soil are already under way. China’s Three-North Shelter Forest ­Program, known as the Great Green Wall, is the world’s largest human-made forest. Upon completion in the 2050s, it will span 4,500 kilometers, slowing the southward advance of the Gobi Desert. However, most places don’t have the political, social or economic structures that permit such sweeping changes to land use. The health of their soils depends upon the choices made by millions of individual farmers. That might just be the best place for the next green revolution to begin.

 

Old trees, new life

Tony Rinaudo, an Australian agronomist, has spent his career helping farmers in the Global South to adopt more ­sustainable practices. His work began in Niger, West Africa, in the early 1980s. “It was a ­landscape on the verge of ecological collapse,” he says. Deforestation had stripped protection from the soil, water shortages were rife, and the Sahara Desert was advancing from the north. Rinaudo’s tree-planting efforts were failing, however: “80 or 90 percent of the saplings we planted died or were destroyed.”

 

He was about to abandon the project. “Then one day I noticed one of the low bushes next to the road, and took a closer look,” he recalls. That bush, like millions of others, turned out to be a tree, ­regrowing from a leftover stump. “In that instant, everything changed. We didn’t need millions of dollars to make a dent in this. We didn’t need a miracle species of tree that could withstand droughts and people pulling them up. Everything you needed was literally at your feet.”

Tony Rinaudo speaking to a camera with four agricultural farmers in the background.

Known as “the forest maker,” Tony Rinaudo helps farmers in Africa and beyond to protect their soils by regrowing trees from left over stumps when land is cleared.

Quote by Tony Rinaudo, an Agronomist: "After 20 years, we had 200 million trees, without planting a single one.”

With well-established root systems to access water and nutrients from deep in the soil, trees that regrow from stumps are much more likely to survive than new seedlings. That revelation shifted Rinaudo’s approach. He started a new project, incentivizing farmers to allow a few trees – 40 per hectare – to regrow on their land. “They thought the idea was strange, but a minority could see it was doing some good,” says Rinaudo. “A ­little more organic matter was going into the soil, wind speeds were slower, the temperature was lower, and some of the traditional wild foods were coming back.”

In the following years, Rinaudo’s “farmer-managed natural regeneration” approach steadily took root in Niger. “After 20 years, we had 200 million trees across 5 million hectares, without planting a single one. All from an investment of about two U.S. dollars per hectare,” he says. Mature trees each absorb about 25 kilograms of carbon from the atmosphere every year, and more is captured by the improved soils on regenerated farms.

 

Rinaudo and his current employer, the charity World Vision, went on to launch projects in other African countries, ­including Ethiopia, Ghana and Senegal. Today, farmer-managed natural ­regeneration is used in about 25 ­countries. Most common in Africa, it has also been adopted in countries such as Indonesia, Myanmar and East Timor.

A single tree in a desert landscape.

Trailer “The Forest Maker”

Tony Rinaudo