The oldest task in human history. To live on a piece of land without spoiling it. –Aldo Leopold
Those words ring quite true to me as springtime is upon us, which means planting season for gardeners and farmers alike.
I found my way into the field of agronomy (or, agricultural science for those less familiar with the term) with a background in climate science and a passion for the environment, realizing that future change posed new challenges to agriculture and the natural resource base that it depends on. I soon came to realize that the soil was a large part of the answer I was seeking—to help food systems adapt and be more resilient to change—and that through caring for that living crust, we can alleviate other environmental burdens.
Soil science 101: the living crust of the Earth (and only a small amount for food)
I heart soil because it is an under-appreciated natural resource. Soil is definitely gaining popularity in the media (the United Nations dedicating the year of 2015 to raising awareness) but we don’t hear about soil nearly as frequently as the water we drink or air we breathe.
What is soil? It is quite literally the living crust of the earth, the interface of geology, biology, and climate. Let me explain. Soil is formed on a geologic timescale, as rocks break down over time thanks to the elements that include climate—rainfall and extreme temperatures the key actors—as well as local biological factors such as plants and animals.
An ideal soil is in large part empty. That is because soils need the proper amount of air, or “porosity” as agronomists would say, in order for water, gases, earthworms, and other critters to cycle through it. The other portion of the soil consists of solid materials, a combination of mineral (mostly derived from the rocks that formed the soil) and organic material (think stuff that was once alive, such as decomposed plant materials that came into the soil).
Soil is not infinite, either. This is a fantastic animation illustrating that roughly 3% of the earth’s surface is actually usable for our own provisions, making its protection one of the critical concerns for 21st century food security.
How humans manage the soil makes a difference
A research plot near Iowa State University with a thick green carpet of a winter rye cover crop. I took this photo in April 2013, after the severe drought in 2012 drought and directly before heavy rains later that spring. I love this visual representing how a plant might help buffer climate impacts to agriculture, for example by protecting the soil from erosion or by improving water infiltration.
All parts of the soil—the solid and the “empty”—are critical to how this foundational resource ensures agriculture’s resilience to future change. A major climate impact that scientists already measure and anticipate more of with a warmer atmosphere is rainfall variability. If we think about the soil as a sponge, it might be easy to understand why we want more sponge “porosity” to absorb excess water in times of heavy rain and to hold on to it for periods of less. In addition to the porosity, the organic portion of the soil is known to be an important component in how much water is stored in the soil.
Ensuring adequate porosity and organic material in the soil to ensure that it behaves like a proper sponge has to do with how we, as humans, manage it: the types of plants grown, the amount of plowing or the use of irrigation all impact the soil. The same way that you might carefully prepare your garden for planting, plan what to plant based on prior years, or apply mulch to retain water are all at play with farming, just on a larger scale.
In my graduate research at Iowa State University I worked with a large team of scientists trying to understand climate change impacts to Midwest agriculture. I specifically focused on the long-term effects growing a cover crop—basically just a plant you would grow not to harvest but to protect the soil—and what effect that had on crop production and the environment in the context of a changing climate. In general we found that a cover crop is an effective tool to significantly reduce erosion and to improve water storage in wet and dry years, but that it did not necessarily reverse soil carbon losses or prevent yield declines under increased temperatures.
In short, cover crops provide some climate buffering benefits, but aren’t a panacea, and won’t prevent all future impacts.
Why agroecology matters for soil and climate adaptation
My prior work was a perfect primer for my research with the Union of Concerned Scientists. We want to know how we might be better buffered against future droughts with more diverse management. What would happen if utilized more ecological practices on the broader landscape? How much additional water might we have in periods of drought? Will this also improve flood impacts?
I want to approach these questions specifically from the soil standpoint. Is improved soil function the reason that prior research has found more diverse crop rotations to improve crop yields in more severe weather years and that conservation practices increase crop yields in drier regions?
Back to my Aldo Leopold quote: to find ways to live on the land without spoiling it is a critical issue requiring sound science at the forefront of discussions. As someone who strives to be an active member of my democracy, I am grateful to get to share more about this important science with a wider audience here.