this graph was created in OurDataWorld:
Agriculture is arguably the industry most sensitive to changes in the climate. Crops need CO2, water — not too little or too much — and the right temperatures to grow. That’s why it’s the impact of climate change that I’m most worried about.
In this 3-part series on climate change and food, I’m going to look at three important questions: how has climate change already affected food production; what could these impacts look like in the future; and how can we feed a growing population in a warmer world?
In this first article, I’ll focus on the first question, looking at how different factors affect plant growth and how large these effects have already been.
You might have heard people argue over whether climate change would help or hurt crop yields.
Some argue that having more CO2 in the atmosphere is good because it increases plant growth, while others argue that higher temperatures reduce growth. Both are true at the same time. The combined impacts on yields vary a lot depending on the type of crop and location.
When considering the net impacts of climate on food production, we need to consider three key factors: higher concentrations of CO2, warmer temperatures, and changes in rainfall (which can cause too much, or not enough, water).1
Let’s look at each of these effects in isolation.
Carbon dioxide helps plants grow in two ways.2
First, it increases the rate of photosynthesis. Plants use sunlight to create sugars out of CO2 and water. When there’s more CO2 in the atmosphere, this process can go faster.
Second, it means plants can use water more efficiently. When there’s more CO2 in the atmosphere, the pores on the surface of the leaves that release water can close slightly, allowing them to take in the same amount of CO2 while losing less water.
Both have a positive impact, CO2 does help plant growth.
But, some crops benefit much more than others. Wheat and rice benefit quite a lot. Maize, millet, and sorghum benefit much less, and only when under water stress conditions. The chart below shows the results of a large review of studies assessing how higher concentrations of CO2 impact crop yields.3 Here, CO2 concentrations were increased from 350 to 570 parts per million (ppm). For context, we’re currently at around 420 ppm, and reaching 570 ppm would mean global temperatures are 2°C to 2.5°C higher than pre-industrial times.
Wheat and rice yields increased by around 15% to 20%. Yields of maize and sorghum responded very little to CO2 under “normal” conditions but increased by 30% under water stress.
While non-cereal crops weren’t included in this review, other studies suggest that crops such as soybeans, potatoes, tomatoes, and other vegetables get large yield benefits from higher CO2 levels.4 Doubling levels of CO2 increased soybean yields by 22% to 45%; potato by 51%; lettuce by 35% to 44%; and tomato by around one-quarter.