Green pastures: can ancient eco-engineering help fix our degraded landscapes?

The search for solutions is urgent, and a growing body of evidence suggests that a modest mound, a simple structure that has been used by farmers for millennia, may play a role.

The most basic ones consist of mounds of earth. From a geoengineering perspective, they are as low-tech as can be, but when strategically built, their impact on the environment can be enormous. Individual programs in climates as diverse as Tanzania and Northern Ireland demonstrate the regenerative power of bunding, and the results can benefit both people and nature.

In Tanzania, the non-profit organization Justdiggit and the LEAD Foundation, in collaboration with local communities, are digging tens of thousands of mounds in drylands to collect rainwater as part of a massive greening effort. supported by the UN.

Angelina Tarimo, LEAD Foundation Coordinator, works with local communities in places like Pembamoto., a village in the Dodoma region, where desertification is a growing threat.

“When you ask the elders what happened in the past, they will tell you that there were rains; it was much greener there than what we see now,” she says. “You know very well that somewhere something went wrong.”

Farming has had a negative impact on the land in Tanzania, Tarimo said, with farmers cutting down trees and native plants to grow crops or overgrazing pastures. This damages the soil structure and makes it more prone to erosion. Because the ground is drier when it rains, water is more likely to run off the surface rather than seep into the ground, washing away fertile soil and continuing the drying cycle.

In 2018, Justdiggit and the LEAD Foundation worked with the village to transform a barren 50-acre test site by excavating a network of semi-circular, elevated perimeter mounds around a shallow trench into which seeds were sown. Mounds measuring approximately five by two meters were laid in an overlapping fish scale pattern, their depression facing up the slope to collect rainwater running off the ground, slowing its movement and allowing it to seep into the ground.

Mounds filled with water after rain.  Water slowly seeps into the ground.

As part of the program, the Pembamoto community agreed to leave the land untouched for two years.

“They were very skeptical of any results as they had not seen grass grow in the area in years,” Tarimo says. But after two years of such success, they decided to extend the fallow period. Not only grass seeds sprouted, but other dormant seeds sprouted, and small mammals returned. Greenery spread far beyond the perimeter of the embankments, covering the previously degraded landscape. “After three years, the grass was taller than me!” Tarimo says.

According to the LEAD coordinator, in August 2021, the community began a sustainable foraging grass collection and sold the surplus to neighboring villages, with the money going towards community development.

Justdiggit has other projects in Central Tanzania, where it says hundreds of villages are working to restore more than 750,000 acres through a variety of methods. To date, over 200,000 embankments have been dug between sites in Tanzania and southern Kenya.

Justdiggit Global Communications Director Wessel van Eeden says getting gardening practices into the hands of farmers is vital.

Along with its partners’ outreach programs that include roadshows, brochures and radio slots, Justdiggit is collaborating with other nonprofits to create the Greener.land digital platform, which details 20 geoengineering interventions to restore degraded areas.

“There are potentially 350 million small farmers in sub-Saharan Africa,” says van Eeden. “The methods … are very simple in technology, require minimal investment, so they can be scaled. All we have to do is tell the right story to the right farmer through the right platform.”

Peatland restoration in Northern Ireland

Cage tying at a former tree plantation in Tullycherry, Northern Ireland.

Cell tying – creating an enclosed space with mounds – has been used around the world for thousands of years to create watertight patches of land ideal for growing crops such as rice. Trials have been carried out in recent years to see if it can restore peatlands in Northern Ireland.

As part of the €4.9 million ($4.9 million) Source To Tap project, Northern Ireland Water and its partners set out to explore whether peatland restoration could be a sustainable and cost-effective way to improve drinking water quality.

Almost 70% Drinking water in Northern Ireland and the Republic of Ireland comes from peatlands that act as a natural filter, explains project leader Diane Foster. If the peatlands are degraded, “it could cause problems,” she adds.
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Trees planted in peatlands intercept rainfall and lower water tables, reducing available moisture for sphagnum moss, the main building material for new peat. As a result, this can cause color fluctuations and turbidity in the water, explains Foster.

On land owned by the Northern Ireland Forest Service in Tullycherry, County Fermanagh, peatlands have been used for a pine plantation. Trees were harvested from a trial plot in 2019, and at the end of 2020, two diggers worked for 11 weeks to create 145 rectangular mounds of cells in an area of ​​just over six hectares (15 acres).

The binding method worked “very, very quickly,” Foster says, recalling how some of the cages overflowed. A team from the University of Ulster collected water samples between February and December 2021. “We don’t have a lot of data,” Foster admits, adding that she would like to secure funding for future research. The results are expected to be published later this year.

“Now this area remains to be restored further,” she adds. “We have installed a mechanism to hopefully keep the water level high… We see it getting greener. We’ve seen the sphagnum moss come back.”

Sphagnum moss, which rots over time, turning into fresh peat.

Although the trial was designed on a per-person basis, the benefits of peatland restoration are manifold. “This will support many different ecosystem services,” says Foster, including “biodiversity, water supply, flood storage, and especially carbon storage.”

Northern Ireland Water is already applying this method elsewhere. In Loch Bradan, which is a source of drinking water, 8 to 10 hectares (20-25 acres) of trees planted on peatlands were cut along the western shore of the reservoir and cell embankments were installed, creating a peat bog to slowly filter the water. flows into the lake.

“(It’s) really exciting to see him out there in that drinking water catchment area,” says Foster. “It will take some time for the sphagnum mosses and everything to settle in, but the process is already underway.”

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