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More water in greener landscapes?

There is an additional story behind the Wyss Academy’s recent success in re-greening part of the landscape in Laikipia County, Kenya: Since September of 2023, members of the East African hub team have been supporting their Research & Innovation colleagues in Bern with a hypothesis. If carbon were added to the soil, would this not only make the land greener, but help it hold more water? Could it even lead to more rain?  

In semi-arid areas around the world, land that was traditionally used as pasture has degraded to a point at which the plants that grow there sustain fewer and fewer animals, and water is becoming ever more scarce. Methods are needed that could be reproduced around the world – that would help turn around this vicious cycle and restore both vegetation and water to the landscape.  

At the same time as our team in Laikipia witnessed massive local support for their bunds project, their colleagues in Bern had already been conducting a study using a digital global land surface model, to simulate the effect of nature-based approaches on the availability of water in the soil. A land surface model is a digital tool that is designed to represent physical, chemical and biological processes of the Earth's surface, and to capture interactions between the land and the atmosphere. Land surface models can predict how climate change and land use affect plant growth, which itself impacts energy, water and carbon exchanges with the atmosphere. They can therefore be used to inform policy about land use and water use management. 

 “The idea of this modelling study originated from the 4 per 1000 Initiative, which was launched at COP21 in Paris and aims to increase soil organic carbon by 0.4 % per year,” explains Dr. Marie-Estelle Demory of the Climate Scenarios and Sustainable Development team. She coordinates the Wyss Academy's interdisciplinary project on water scarcity and in this capacity, has been overseeing the integration of the modelling study into the local context in Kenya. Prof. Dr. Édouard Davin suggested the hypothesis that increased soil carbon storage could have co-benefits for the water cycle, by retaining more soil moisture. Dr. Inne Vanderkelen, a former team member, offered to test this hypothesis with a land surface model. The model was then presented by Édouard Davin at the Wyss Academy’s planning week retreat in September. 

It was there that the Wyss Academy’s close integration of its researchers with the work done in the Hubs bore fruit. “Édouard and I discussed it with Sheila Funnell, the Hub East Africa’s Head of Innovation and Impact, and brainstormed on how to test carbon sequestration using the already ongoing semi-circular bunds,” says Marie-Estelle Demory. “The idea of depositing a thin layer of biochar beneath the surface of the soil came up, and Sheila and Antony Wandera (the Hub’s Project Manager) took it over and did it.”    

Biochar is a type of charcoal made from organic materials, such as agricultural waste or wood. The Hub team dug two additional bunds and planted soil sensors in each of them. According to Marie-Estelle Demory, “with continuous monitoring, they were able to verify on site the hypothesis that increasing soil carbon content increases soil moisture.” Some things turned out to be more complicated than the hypothesis assumed. The positive effect on soil moisture, for example, depends on soil and climate conditions. According to Professor Davin, "the modelling study will enable us to derive more general conclusions that will help us if we want to upscale this strategy." 

Plant growth, combined with an increase in soil moisture would increase the flow of moisture to the atmosphere, which in turn would have a positive effect on local rainfall. It has the potential to effectively restore the water cycle in semi-arid regions.  

For the time being, however, open questions remain. Such as: How accessible is the moisture in semi-circular bunds to the plants that grow within them? In what has grown into an interdisciplinary effort, the semi-circular bunds in Laikipia County will continue to be monitored by Hub East Africa, together with their colleagues from the Innovative Technology, Integrative Biodiversity Conservation Science, and Climate Scenarios and Sustainable Development teams.  More on how the Wyss Academy is studying the effects of semi-circular bunds on local biodiversity can be found here.


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