We even define ourselves by our relationship to soil: the words “human” and “humanity” are linguistically rooted in “humus” – which is the fertile upper portion of the soil.
In spite of the connections, many of us fail to consider the importance of preserving the health of the earth’s soils for now and generations to come.
In Sub-Saharan Africa, where the population will more than double by 2050, an estimated 65 per cent of soils are degraded.  This translates to poor harvests, malnutrition and chronic hunger for millions.
When we think about the role of soil in the food security equation, it’s no wonder that the UN General Assembly chose to designate 2015 the International Year of Soils.
“Many of us fail to consider the importance of preserving the health of the earth’s soils for now and generations to come.”
David Guerena and Margaret Vernon, One Acre Fund
With more than half the world moving to urban areas by 2050 [ 3], it’s important that we take time to appreciate our relationship to soil, and discuss what we can do to keep it healthy, and how soil health can even help us achieve the UN’s Sustainable Development Goals (SDGs).
Crucial and last frontier
Seventy per cent of poor people in rural areas depend on agriculture for their livelihoods.  These rural areas comprise large numbers of smallholder farmers, who cultivate less than two acres of land.
Lacking access to quality inputs, tools training, and financing, smallholder farmers are often at the mercy of unproductive soil. Promoting soil health, through strategies such as agroforestry, intercropping and composting is one important way to increase the productivity of these small plots of land.
These strategies could help smallholder farming communities increase their resilience to environmental shocks and grow their way out of hunger and poverty.
Soil is the greatest reservoir and the last frontier of biodiversity. Most known antibiotics come from organisms that were isolated from the soil. The soil biosphere controls the cycling of most major plant nutrients, such as nitrogen, phosphorus, and sulfur. What other secrets are held in the soil biosphere? In one gram (one pinch) of soil, there are over one billion individual organisms and over one million unique species!  We know less than one per cent of who they are and less than one per cent of one per cent of what they do.
Non-renewable and climate change
Soil is a highly valuable — and non-renewable — resource.
According to The Land Institute, an organisation based in the United States that facilitates alternative strategies to current agricultural practices, soil is every bit as non-renewable as oil, and it is essential for human survival. It takes thousands of years to develop just a few inches of soil. A rich, deep soil that may have taken more than 100,000 years to form can be lost overnight through soil erosion.
We can think of soils as a very thin skin that surrounds earth, connecting the atmosphere, biosphere, hydrosphere and geosphere.
Franklin D. Roosevelt once said: “A nation that destroys its soils destroys itself.”
We can’t combat climate change without focusing on soil. Climate change is driven by atmospheric carbon. Surprisingly, soil can absorb nearly twice as much carbon as can be contained within plants and the atmosphere combined!
Soil’s enormous capacity to absorb more carbon has additional benefits: adding carbon to the soil through plant materials such as compost, green manure, animal manure and biochar will actually reduce carbon, and thereby the amount of carbon dioxide in the atmosphere. Increasing the amount of carbon in soil will also allow the soil to capture and hold more rainwater, which reduces the amount of soil erosion and increases the soil’s ability to filter ground water, which increases water quality.
Innovation and perseverance
Ensuring soil health involves innovation and perseverance. Agriculture for Impact, a UK-based advocacy initiative, recently released a Montpellier Panel report in which the authors call for a ‘big data’ revolution to amass helpful data on soil type and quality. 
The Alliance for a Green Revolution in Africa has trained almost two million smallholder farmers in 13 countries — including Burkina Faso, Ethiopia, Ghana, Kenya, Malawi, Nigeria and Zambia — in integrated soil fertility management practices, helping them acquire the inputs they need to revive their lands and boost their yields, according to its website.
One Acre Fund, an organisation that serves smallholders in Burundi, Kenya, Rwanda and Tanzania, trains farmers in these countries on intercropping and composting techniques, and offers loan products, including solar lights, which have positive environmental impacts.
For example, Grevillea trees, which the organisation is helping smallholders to cultivate to boost their incomes, require less water and land than many other species such as Eucalyptus. These efforts to improve soil health may take time to produce results, but will ultimately ensure that existing farmland is more productive for generations to come.
“If we truly want to achieve the Sustainable Development Goals we’ve set for ourselves, we can’t afford to not focus on soil health, this year and every year.”
David Guerena and Margaret Vernon, One Acre Fund
Soil is part of the solution to some of the greatest dilemmas of our time. It plays a critical role in mitigating the effects of climate change, increasing farm productivity and food security, and may hold the answers to eradicating antibiotic resistance.
If we truly want to achieve the Sustainable Development Goals we’ve set for ourselves, we can’t afford to not focus on soil health, this year and every year.
David Guerena holds a PhD. In soil science and is the agricultural innovations manager for One Acre Fund. He lives in Kisumu, Kenya. He can be reached on [email protected]
Margaret Vernon is the country director for One Acre Fund in Burundi. Margaret has worked with One Acre Fund since 2008 and lives in Muramvya. She can be reached on [email protected]
This article has been produced by SciDev.Net’s Sub-Saharan Africa desk.