On June 2, Climate Classes partnered with Common Good City Farm and World Central Kitchen to host a cooking class, which included a discussion on modern agriculture’s effect on the environment and how small, local farms are part of the solution to food insecurity and reconnecting with food sources. In the changing climate, private and public actors are attempting to understand the impacts that climate change will have on economies and even national security. However, the impacts of climate change on agriculture are equally as important. 

Here, we will discuss one aspect of climate change in agriculture: water. For this discussion, we must first consider atmospheric thermodynamics. In meteorology, there is a relationship known as the Clausius–Clapeyron relation, which states that the atmosphere can hold exponentially more moisture with a linear increase in temperature. This relationship has implications for how the atmosphere responds during extreme weather events (think: droughts, hurricanes, wildfires, etc.), which are more likely in a warming climate. While it may sound counter-intuitive, a warmer atmosphere that holds more moisture is bad for both wet and dry extremes. In such a scenario, a warmer atmosphere means that intense storm systems hold more moisture while a hot and dry atmosphere evaporates more water. As the meteorologists’ favorite saying goes, “The wet gets wetter, and the dry gets drier.”

This increased propensity for wet and dry extremes in a warming climate can have a variety of impacts on agriculture. In a world more prone to extreme rainfall, disturbances to agriculture caused by extreme precipitation can result in lost yields. For example, in 2019, the Mississippi basin flooded and due to an inability to plant in flooded fields, more than $20 Billion in total losses including some corn and soybean crops were attributed to this event. 

Dry extremes can be equally detrimental to agriculture. In the southwest United States, California, Arizona, Nevada, Utah, New Mexico, Colorado, and Nevada all share water from the Colorado River basin. This water is used for agriculture, industry, and by cities. The Colorado River is already over-allocated (the Colorado River compact that governs water-rights assumes annual flows that are greater than actually observed), and recent droughts that have been made worse by climate change mean that water stored in reservoirs is used but not replaced. If this drought persists, Western states will have to choose between irrigated crops and maintaining the water needs for growing urban populations. 

In some regions, both wet and dry extremes may create challenges when managing water in a warming climate. For example, the central valley in California gets much of its streamflow for irrigated agriculture from mountain snowpack. In wet years, water may be held in reservoirs to prevent flooding, and can be released in dry years when less water is available. In a warming world, the jet stream (the fast current of moving air that separates warm and cold air) can become more amplified and lead to both cold and wet extremes and warm and dry extremes. These amplified patterns could mean that more water must be released from reservoirs to prevent damage to the structure of a dam during times of high streamflow. Meanwhile, this leaves less water available to farmers during more extreme droughts. In other words, a world where most rainfall occurs from a few extreme events is not favorable for agriculture, nor for water management more broadly.

A changing climate that is more prone to droughts and other disturbances from extreme events will be more prone to crop failures and famines. 

In the changing climate, smaller farming operations are more able to tolerate extreme water events, although they are still subject to changing weather events.