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The health of the Earth's soil is crucial to storing carbon.
So what does it mean when scientists conclude the Earth’s soil is being lost 10 to 100 times faster than it is forming?
“It's undermining our ability for long term sustainability, in a nutshell,” scientist Louis Verchot says.
He’s one of the scientists on the United Nations Intergovernmental Panel on Climate Change (IPCC) who revealed the alarming rate at which soil is being lost.
Soil condition mediates many of the processes that affect the climate — from plant growth to carbon dioxide intake. He says soil stores about twice as much carbon as the atmosphere.
Mismanagement of land and the effects of climate change — including mega droughts or massive floods — “significantly limits the ability to rebuild” the soil’s ecosystem, he says.
When the soil can’t replenish and ultimately degrades, it leads to a release of carbon into the atmosphere. Verchot estimates roughly half of the U.S.’s argicultral lands and a third of the forests have degraded soils.
“We're losing soil quality and soil function fairly rapidly due to unsustainable management practices,” he says. “This has an impact on the ability of the biosphere to support the production of food [and] support all the processes and services that we get from healthy agricultural and natural ecosystems.”
On why soil is so important to the atmosphere and an important factor when talking about climate change
“It's the basis for plant growth. And so if we have degraded soils, we get poor plant growth. We get reduced carbon dioxide uptake from the atmosphere. Drier soils and warmer soils tend to promote heatwaves. For example, there's a lot of the impacts between the biosphere and the atmosphere, we say are mediated by what we would call the carbon cycle, so plant growth, decomposition, decay and that water cycle so rainfall, and there's a lot of heat that's transferred from the soil to the atmosphere as water vapor or as what we would call sensible heat, so heat that you can feel, and so soils mediate these flows within the environment and have important direct effects on the climate system, but also important feedback effects on the climate system — depending upon how the climate is changing and how the soil conditions are changing.”
On what can be done to increase healthy soil
“There's a lot that can be done to maintain soil health and there's a lot of efforts within the scientific community to do that. There's a lot of efforts within the farming community. We have a lot of investment in what we call conservation agriculture which includes reducing tillage, maintaining soil cover, protecting the soil from erosion [and] rotating crops so that we are maintaining the soil biological function — the microbes and insects and other organisms in soils that are essential for soil health.
“So there's a lot that can be done. You mentioned the increase of agriculture to the north. These are soils that have typically not been under agriculture and so opening them up to a new agriculture raises questions about the sustainability of this. So if we're going to subject these soils to the same types of degradation that we've seen elsewhere, we're going to also limit our ability to produce the food in the fiber. But at the same time, these areas also are typically not areas that are under agriculture, so we're going to be losing other functions [and] other roles that these soils and the ecosystems on these soils have been playing with respect to forest cover to biodiversity to water resources to carbon stores and the like. And the real danger is the loss in the temperate end that the tropical zones of soil functions.”
On why scientists are concerned about the soil in tropical zones
“Because this is where the population is. So we have the largest population growth right now in the tropics. We're expecting another two and a half to 3 billion people on the planet by 2050, largely in the tropical regions. Producing in the boreal zone isn't a solution to maintaining the sustainability of these populations and the health of these populations in the tropical zone. So as we see increased accelerated tropical soil degradation, we see more and more pressure on the landscape maintaining healthy soils in these regions is really what's essential.”
On the nutrients in degraded soil, and what that does to our fruits, vegetables, etc.
“That's a real danger. Some nutrients are replaceable, things like nitrogen we can replace through biological processes like nitrogen fixation. What's really the risk are some of the micro nutrients so boron, zinc, nutrients that we need that are essential for us in small quantities for maintaining our own health, maintaining the health of the animals that are living on these landscapes [and] the livestock that we're raising. As we see increased erosion, as we see increased depletion of nutrients of organic matter in soils, we're going to see increased nutrient deficiency. This is one of the things we're seeing very much in the tropics and in some parts of the temperate zone now. People that are depending upon these landscapes are often deficient in micronutrients, Vitamin A, iron, zinc, in particular, boron. These issues are are important now and they're gaining importance.”
On climate change’s impact on soil
“As we increase erosion in these massive flooding events than we do in low intensity events, over the course of a year or a decade this soil, as we noted in the IPCC report, we're losing it at about 10 times the rate that it's forming. So if we lose it, it's gone for decades to centuries and significantly limits the ability to rebuild after these floods or after these drought events. Additionally the loss of many of these ecosystems exacerbate these events. So as we lose wetlands in the landscape, we lose water storage. As we lose forests, we lose the absorptive capacity. We increase the velocity of runoff across these landscapes — the water that hits the land and just runs off rather than soaking in — because these ecosystems and the soils underneath these ecosystems can no longer absorb the water.”
On what needs to be done to keep soil healthy
“I think we know pretty well what is required to be done and the economic incentives aren't always aligned to do that. So what we need to do is rotate crops. We need to reduce tillage. We need to maintain soil cover. We need to replace fertility that's lost. As we take crops off, we take nutrients off. We need those need to be replaced through organic or chemical means. We need to use agro chemicals wisely and we're not doing that in many places today. We need to find balances in these landscapes so landscapes function well when there are multiple ecosystems in the landscapes. So we need a diversity of ecosystems in landscapes. We need to manage landscapes more as integral units rather than each individual doing what they think is best for themselves on one particular landscape or one particular farm. We need to understand how different parts of the landscape relate to each other and develop planning and management around these ideas. I think how to manage landscapes and how to keep them healthy is well within the scientific knowledge. It's not that much of a mystery, but getting incentives right to do that right now is the major constraint.”
On what you personally can do to maintain healthy soil
“I think if you're managing land, you need to look for the health of your land. So if you're a farmer, protect your soil. Put in erosion control structures. Put in the nutrients that you need, but not too many nutrients. A lot of the problem we have right now is over fertilization [and] overuse of chemicals. Use organic nutrient sources because these helped build up organic matter and retain nutrients in soils. Reduce tillage and if you're a homeowner, be careful of the fertilizer that you're using. Don't over fertilize your lands. Realize that there are streams and rivers running through your landscape. Protect riparian landscapes and communities. These forests or shrub lands that are along the edges of rivers are really important. They play an important filter function in landscapes to maintain healthy rivers and streams. So I think understanding that what we do has an impact off of the land that we're managing and understanding what we can do to minimize those negative effects on what we're doing is really the approach people need to take as they manage their lands and make decisions about their land.”
This segment aired on September 20, 2019.