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Soil is washing away at unprecedented rates - and it could get worse
Ahead of the Global Landscape Forum in Peru, it helps to remember exactly why landscapes are important. They give us the bigger picture, to connect the dots between the many people who use an ecosystem and what for.
It’s that bigger picture which helps put climate change into perspective. In Kenya’s Tana River watershed, changing weather can have a major knock-on impact on soil degradation in the watershed.
Climate maps projecting possible climate scenarios to 2050 for crop suitability around Kenya’s largest Tana River show the link with increasing soil erosion.
“Soil is washing down Kenya’s 1000km long Tana River at unprecedented rates,” said Fred Kizito, a Senior Scientist at the International Center for Tropical Agriculture, which led the research together with The Nature Conservancy in Kenya.
“In the last 10 years, research shows sediment yields have jumped more than 30 percent - not due to increased rainfall, but damaging agricultural and industrial practices, like farming or quarrying on steep slopes,” he said.
Under certain scenarios, climate maps show that land currently planted to tea could become more suitable for maize or beans in future in certain areas.
If tea - which provides good cover for soil from rainwater runoff - is replaced by maize or beans without good soil management practices, scenario assessments from hydrological models indicate that run-off will increase.
Tea replacement by agriculture in both the Sagana and Thika watersheds of the Tana River basin could see soil sediment yields increase 23 tonnes per hectare and 28 tonnes per hectare: increments of 8 percent and 31 percent respectively.
Soil run-off could be exacerbated if, as the study suggests, rainfall increases another five percent.
This research shows how upstream dynamics are contributing to soil sedimentation and degraded water quality in downstream urban water supplies.
There is a solution being piloted: The Nairobi Water Fund, set to launch next year, will be a first for Africa. All eyes – and a lot of money – are resting on it.
Managed by The Nature Conservancy’s Fred Kihara, downstream members - big businesses like Coca Cola and utility companies - provide financial and technical support to watershed keepers.
To date, The Water Fund has raised $900,000, supporting 5,000 upstream land owners to conserve soil and water in the Upper Tana River watershed. “That’s exciting: downstream users are willing to invest in conservation, and upstream users are willing to adapt.” It makes business sense, said Kihara.
Nairobi City Water and Sewerage Company - which supplies 95 percent of Nairobi’s drinking water - spends 40 percent more during the rainy season, cleaning soil sediment out of water clarifiers.
Not only does cleaning cost more in labor and imported chemicals; intensive cleaning slows water treatment and reduces flow.
KenGen, which supplies 70 percent of Kenya’s electricity, says reduced water flow for hydropower generation prompts occasional shifts to expensive thermal powered alternatives. It makes business sense to invest in long-term solutions.
Researchers from CIAT and partners proves that targeted investments can yield a sustainable benefits for all. Best investment options have been mapped, and costs determined thorough complex soil and hydrological data, to inform Fund members about where and how much money to invest in conservation activities.
The Water Fund concept has worked before in a number of watersheds. In Ecuador, The Nature Conservancy’s Water Fund started with $21,000 investment in an endowment. It has grown to be worth over $10 million in ten years.
Such holistic options, which take the stories of everyone using ecosystems into account, have some important lessons to share.