Agriculture is the foundation of civilization. The word “civilization” comes from the Latin word “civilis,” meaning behavior befitting of a citizen of a city, which is to be courteous and polite, not savage or rude. Our modern, technologically advanced civilization depends on agriculture and the food security it provides so that people can be civil to each other and live peaceful and productive lives. If food security ends, famine can occur, and civility breaks down. Nations risk internal strife, possibly rebellion or revolution, under this scenario.
In the U.S., it’s been easy to take agriculture and food security for granted. (Note: Food security is another way to say, “hunger prevention.”) Since the Great Depression of the early 20th century, food has been plentiful and relatively inexpensive for most Americans. Recently, however, prices, such as eggs, have been rising due to a number of factors including HPAI H5N1 (bird flu) killing chickens.
Throughout much of history, however, food security has been more the exception than the rule. Many countries, particularly in Africa, Asia, and South America, contend with considerable food insecurity. In the 21st century, agriculture is in danger from a number of threats, most notably, soil depletion and climate change. In this blog, I will discuss each and conclude with a One Health perspective.
Soil Depletion
Plants need air, water, light, appropriate temperatures, and rich soils filled with nutrients and organic materials to thrive and be healthy. (Note: There are technologies called “aeroponics” or “hydroponics” that grow plants without soil. It’s unlikely that the costs of growing plants this way would be low enough to feed billions of people.)
From the 1940s to 1960s, the Rockefeller Foundation funded research in Mexico to develop disease-resistant, high-yield varieties of wheat. Dr. Norman E. Borlaug, an American plant pathologist and geneticist led this research and developed new agricultural technologies and practices to stave off famine in developing countries, particularly India. Crop yields skyrocketed while land use remained essentially unchanged, as illustrated in the graph below. The results were so successful that it was call the Green Revolution. For his efforts, Borlaug won the Nobel Peace Prize.
But the benefits of the Green Revolution came with costs. Soil depletion refers to the loss of the nutrient cycle, namely nitrogen, phosphorous, and potassium, that plants need to grow. Historically, plants and animals lived together on farms. Grazing animals would churn and aerate the soil with their hooves and defecate their manure, helping to maintain the nutrient cycle.
Modern agriculture has separated crops from animals.
Instead of grazing animals and mixing crops, it relies on high nitrogen synthetic fertilizers, monocrops, lack of crop rotation, intensive water use, inadequate irrigation systems, tillage, and pesticides to maximize crop yields. Each of these practices present sustainability challenges. Over reliance on high nitrogen synthetic fertilizers, for example, has contributed to soil depletion, erosion, and nitrous oxide emissions. The UN Food and Agriculture Organization (FAO) provides extensive information on the state of the world’s soils.
Animals are now kept in Concentrated Animal Feeding Operations (CAFOs), highly efficient in raising large numbers of food animals, but pose serious ethical concerns and generate massive amounts of wastes. Manure is typically stored in giant lagoons contributing to environmental pollution.
North America, Europe, and to a lesser extent, Asia have relied on high nitrogen synthetic fertilizers for crop agriculture for many decades. (See the graphs below. Manure use is in blue, and high nitrogen synthetic fertilizer use is in red).
(Data from FAOSTAT from the UN Food and Agriculture Organization (FAO)).
North America (1961-2024)
Europe (1961-2024)
Asia (1961-2024)
In South America and Africa, high nitrogen synthetic fertilizer use has not exceeded manure use.
South America (1961-2024)
Africa (1961-2024)
While animal manure can harbor dangerous pathogens, it provides soils with much needed organic matter that synthetic fertilizer lacks. To reduce pathogen contamination risks, such as Salmonella enterica, manure should be processed before being applied to agricultural fields. One processing strategy might be the application of bacteriophage mixtures in manure composts to remove pathogens.
Climate Change
Understanding climate change requires thinking like a geologist. Examining the geologic timeline of the temperature of Earth since 500 million years ago, reveals that Earth was once a very hot planet. During the Phanerozoic era, the land was barren, carbon dioxide levels were high, and much of the planet was covered by warm, shallow seas.
Photosynthetic algae removed atmospheric carbon dioxide and produced oxygen, creating the conditions for life on land.
Over millions of years, the planet cooled. The Ice Age occurred during the Pleistocene era. Inexplicably, around 10,000 years ago, at the beginning of the Holocene era, the planet warmed. It’s no coincidence that agriculture began around 10,000 years ago. Agriculture developed because Earth’s temperature allowed it, unlike the preceding Ice Age.
Indeed, for the entire Holocene era, the climate has been remarkably stable and predictable, allowing farmers to plant seeds in the spring and harvest crops in the fall. (To visualize the Holocene baseline, please see the graph above.)
There was one notable exception.
During the Little Ice Age, beginning around the 14th century, temperatures dropped approximately 2 degrees Celsius (or 3.6 degrees Fahrenheit) below the Holocene baseline. The effects on agriculture were global and catastrophic, particularly in Europe. Grain harvests plummeted leading to food riots, rebellions, and witch trials, because some people had to be blamed for the failed harvests.
Now, human-derived greenhouse gas emissions are causing Earth’s temperature to deviate off the Holocene baseline, but this time, about 1.2 degrees Celsius (or 2 degrees Fahrenheit) above the baseline, making the planet hotter. The UN’s goal is to limit the deviation above the Holocene baseline to no more than 1.5 degrees Celsius. Obviously, the closer Earth’s temperature stays to the Holocene baseline, the better it is for agriculture, food security, and civilization. But if current policies continue, the temperature deviation could be a disastrous 2.5 to 2.9 degrees Celsius above the baseline. (Please see graph below.)
Ironically, while agriculture is threatened by climate change, it also contributes to climate change. Its most potent greenhouse gas emissions, notably methane (CH4) and nitrous oxide (N2O) contribute almost a quarter of total greenhouse gas emissions.
Cattle and other ruminants have four chambered stomachs, one of which is the rumen which ferments feedstuffs, releasing methane. The ruminants burp and release it into the atmosphere, contributing 25 percent of methane emissions.
While methane and nitrous oxide don’t last as long in the atmosphere as carbon dioxide, they are much more potent at trapping heat into the atmosphere than carbon dioxide.
The planet Venus is an example of what happens when greenhouse gasses run amok. While Venus might have been habitable at one time, after all, its similar to Earth in mass and size, but its surface temperature is greater than 460 degrees Celsius, hot enough to melt lead. Most of its atmosphere is carbon dioxide, a greenhouse gas.
The use of high nitrogen synthetic fertilizers on agricultural fields is a major source of nitrous oxide.
Manure also contributes nitrous oxide and methane, especially if it’s improperly managed. There are strategies to reduce its emissions including anaerobic digesters, improving storage and handling, and altering livestock diets.
One Health
From a One Health perspective, using treated manure to remove pathogens would provide soils with much needed organic matter.
Strategies to reduce nitrous oxide emissions from agriculture have been developed. Low nitrogen synthetic fertilizers mixed with animal manure would help with both soil replenishment and reduce nitrous oxide emissions. Developing feedstuff supplements, such as seaweed, to reduce methane emissions in cattles’ rumens helps.
Soils should be rotated to allow recovery from intensive farming practices. This isn’t new thinking. In the Old Testament, biblical agricultural laws mandated resting the land from use every seven years. The ancients recognized the need for soil to replenish its nutrients and organic matter.
Recognition of agriculture’s role in climate change is growing. At COP29, a declaration to reduce methane emissions from organic waste in landfills was made. But much more must be done. Agricultural scientists, farmers, climate change activists, and One Health advocates must work together to highlight the critical role that agriculture and food security have on global health and civilization.