As if the world needed another environmental crisis to worry about, a 2014 study suggests that if we continue at our current rate of degradation, all of the world’s topsoil will be gone in 60 years. But what is topsoil? And why should you care? Here are some of the core concepts to get you up to speed on the soil conservation movement.
Soils need a healthy layer of topsoil, but this is becoming less and less common (Image Source: Pike Conservation)
What is topsoil? And where is it going?
While the phrase “soil conservation” might make it sound like our soils are in danger of extinction like the polar bear, soil conservationists are fighting against something more subtle. Soil is being stripped of its nutrients by commercial agricultural practices and eroded away into nearby bodies of water. That leaves remaining soils unusable by plants and animals that need them. The World Wildlife Federation estimates that 50% of the world’s topsoil has been lost in the last 150 years
When people are talking about soil conservation, usually they really mean topsoil. Topsoil is the nutrient-rich soil located just under any twigs, leaves, or other organic matter that might be on the ground. For many plants, this topsoil is where they find most of the nutrients needed to grow.
How are humans burning through a resource as valuable as topsoil so quickly? Similar to fossil fuels like coal, topsoil can form naturally, but at a pace of only 0.25-1.5 mm annually. Soil accumulation simply can’t keep up with large scale commercial agriculture practices and other land degradation.
What does this have to do with people?
A lot! Humans might think we’re above nature, but our fates are tied far more closely to the dirt than we’d like to admit. Research suggests that agricultural fields’ productivity decreases as soil becomes more degraded. This is a huge problem, especially considering that 95% of the world’s crops need topsoil to grow, and the UN reports that a third of the world’s soils are no longer considered productive.
As if a depleted food supply isn’t a big enough threat, soil degradation also has the potential to speed up the effects of climate change. The organic parts of topsoil that still exist store a huge amount of carbon. If they’re lost, this carbon has to go somewhere, and that somewhere is likely the atmosphere. This will worsen the already dire extent of human-caused climate change.
Can’t we just add more worms?
Sadly for all worm lovers, no. While most of us have heard about the importance of worms, such facts tend to oversimplify worms’ complex role in ecosystems.
Earthworms can have tremendous benefits for soil health, including increasing the amount of nutrients in the soil and facilitating water drainage. But not all worms are created equal. Invasive earthworms have set up shop in the U.S., and eat through organic matter much faster than their native counterparts. Native plants and animals aren’t adapted to these changed soils and may depend on the now-eaten organic matter to survive. These worms threaten forests where they change ecosystem composition literally from the ground up.
Not just forests are in trouble though. These worms spread quickly with human disturbance and pose a threat to farmlands too. Many of the worms sold in bulk for agriculture and composting are non-native varieties. Unless the supply of native earthworms changes drastically, just putting more worms onto fields isn’t going to cut it.
Invasive earthworms look innocuous but can destroy entire ecosystems (Image Source: LTER Network)
What can farmers do about it?
A rarity for environmental problems, there’s good news here. Farmers can implement key steps to conserve topsoil.
One simple suggestion: make sure that bare soil isn’t exposed to the harsh sun and eroding rain for long periods of time. There are several ways to make this happen, including leaving some of the inedible parts of crops on the ground after harvest and planting a “cover crop” to act like a blanket for the soil between growing seasons.
Other ways to support soil conservation in agriculture would require a more substantial shift in farming practices, but could lead to a larger shift in soil health. Practices like “strip cropping,” where farmers grow different crops side by side in a field, can prevent erosion with the variety of root lengths that it creates underground.
Growing more than one crop at a time has other benefits too. If plant neighbors are chosen carefully, they can support each other’s growth. This natural supply of nutrients can also help prevent the need for harsh fertilizers, which can mess up both the farmland where they’re used and surrounding areas.
“Strip Cropping” agriculture can help conserve soil long-term (Image Source: Encyclopedia Britannica)
I’m not a farmer—what can I do about it?
Non-farmers can also get involved in the soil conservation movement, albeit on a different scale. Avoid using fertilizers and pesticides on your garden or lawn to support soil health in your own backyard. If your lawn can’t make it without these chemical helpers, consider planting a new species of grass or foregoing the green lawn look altogether.
Urging policymakers to prioritize soil conservation and advocating for sustainably and justly grown produce for all can also help spark conversation about soil conservation locally. Let them know that the idea of soil conservation isn’t new, but it is more relevant than ever.
Regardless of what we do, it needs to happen before the second half of the world’s topsoil is gone for good.