Growing change: Can agriculture be good for the climate?
Aug 2, 2019 at 12:45pm
Last year California set a goal to become carbon-neutral by 2045. Some called it unrealistic, while we call it mission-critical. But how do we get there? As we search for ways to reduce greenhouse gas emissions to prevent global atmospheric temperatures from rising above 1.5 degrees and result in irreversible climate change, one of the best answers is as old as the dirt under our feet, literally.
Let’s go back to basic science. Soil naturally has large amounts of carbon. Healthy soil — soil rich in nutrients and able to retain water — holds the carbon that plants absorb from the air and bring into their root system and sequester in the soil as root and plant matter decompose. Also, healthy soil is teeming with microbes which also bring carbon deep in the soil.
Agricultural scientists across the globe, including at Stanford University and the University of California, Davis, have in recent years been making new discoveries showing that healthy soil holds more carbon than previously thought and that good soil management can serve as an important carbon sink. Soil, writes Rob Jackson of Stanford’s Woods Institute for the Environment, "is a no-risk climate solution with big co-benefits. Fostering soil health protects food security and builds resilience to droughts, floods and urbanization."
Unfortunately, over the last half-century of primarily monocrop agriculture, repeated plowing and regular use of pesticides and chemical fertilizers, the average amount of carbon content in agricultural soil gradually has depleted, according to studies, which has led to the need for more fertilizer to maintain production levels. Between synthetic fertilizer and cattle growing via confined animal feeding operations to satisfy a world population hungry for meat, agriculture is a net carbon emitter — a substantial one. Agriculture accounts for about 13 percent of global greenhouse gas (GHG) emissions and 9 percent of U.S. emissions, according to the U.S. Environmental Protection Agency. When including the emissions resulting from clearing forested land to plant crops, those numbers are even bigger.
But lately, a healthy soil movement has taken hold, focused on practices referred to as regenerative farming, offering intriguing possibilities of agriculture as a carbon sink. Often born of necessity as farmers grapple with less water, increased erosion and the rising costs of chemical fertilizer, some farmers are adopting a set of practices to make soil resilient, rich and in need of fewer inputs — and it so happens such soil is better at storing carbon underground. These regenerative practices include reduced tilling to keep decomposing organic matter in the soil; planting off-season cover crops which bring new nutrients to the soil and protect it from erosion; using compost and manure as fertilizer; and rotating crops and animal grazing among fields to give soil a chance to replenish. Collectively, these practices reduce the need for irrigation, fertilizer and herbicides.