How Climate Change will affect Plants

By Renee Cho

We human beings need plants for our survival. Everything we eat consists of plants or animals that depend on plants somewhere along the food chain. Plants also form the backbone of natural ecosystems, and they absorb about 30 percent of all the carbon dioxide emitted by humans each year. But as the impacts of climate change worsen, how are higher levels of CO₂ in the atmosphere and warmer temperatures affecting the plant world?

CO₂ boosts plant productivity

Plants use sunlight, carbon dioxide from the atmosphere, and water for photosynthesis to produce oxygen and carbohydrates that plants use for energy and growth.

Rising levels of CO₂ in the atmosphere drive an increase in plant photosynthesis—an effect known as the carbon fertilization effect. New research has found that between 1982 and 2020, global plant photosynthesis grew 12 percent, tracking CO₂ levels in the atmosphere as they rose 17 percent. The vast majority of this increase in photosynthesis was due to carbon dioxide fertilization.

Increased photosynthesis results in more growth in some plants. Scientists have found that in response to elevated CO₂ levels, above-ground plant growth increased an average of 21 percent, while below-ground growth increased 28 percent. As a result, some crops such as wheat, rice and soybeans are expected to benefit from increased CO₂ with an increase in yields from 12 to 14 percent. The growth of some tropical and sub-tropical grasses and several important crops, including corn, sugar cane, sorghum, and millet, however, are not as affected by increased CO₂.

Under elevated CO₂ concentrations, plants use less water during photosynthesis. Plants have openings called stomata that allow CO₂ to be absorbed and moisture to be released into the atmosphere. When CO₂ levels rise, plants can maintain a high rate of photosynthesis and partially close their stomata, which can decrease a plant's water loss between 5 and 20 percent. Scientists have speculated that this could result in plants releasing less water to the atmosphere, thus keeping more on land, in the soil and streams.

But other factors count

Elevated levels of CO₂ from climate change may enable plants to benefit from the carbon fertilization effect and use less water to grow, but it's not all good news for plants. It's more complicated than that, because climate change is also impacting other factors critical to plants' growth, such as nutrients, temperature, and water.