How climate change will affect plants
We humans need plants to survive. Everything we eat consists of plants or animals that depend on plants somewhere in the food chain. Plants are also the backbone of natural ecosystems, absorbing about 30 percent of the carbon dioxide humans emit each year. But as the effects of climate change worsen, how are higher levels of carbon dioxide in the atmosphere and higher temperatures affecting the plant world?
Carbon dioxide boosts plant productivity
Plants use sunlight, atmospheric carbon dioxide, and water for photosynthesis to produce oxygen and carbohydrates that plants use for energy and growth.
Rising carbon dioxide levels in the atmosphere drive increased photosynthesis in plants — an effect known as Carbon Fertilizer Effect. new research The study found that from 1982 to 2020, global plant photosynthesis increased by 12%, and atmospheric carbon dioxide levels rose by 17%. Much of this increase in photosynthesis is due to carbon dioxide fertilization.
Increased photosynthesis leads to more growth in some plants. scientists found Above-ground plant growth increased by an average of 21 percent in response to rising carbon dioxide levels, while below-ground plant growth increased by 28 percent. As a result, some crops such as wheat, rice and soybeans are expected to benefit from the increase in carbon dioxide, with yields increasing by 12% to 14%. However, the growth of some tropical and subtropical grasses and several important crops such as maize, sugarcane, sorghum and millet is not affected by the increase in carbon dioxide.
Fir needle-like pores that allow carbon dioxide to enter and water vapor to escape. Photo: OSU
With elevated carbon dioxide levels, plants use less water during photosynthesis. Plants have openings called stomata that absorb carbon dioxide and release water into the atmosphere. When carbon dioxide levels rise, plants can maintain a higher rate of photosynthesis and partially close their stomata, which can reduce the plant’s water loss by 5 to 20 percent. Scientists speculate that this could cause plants to release less water into the atmosphere, leaving more water on land, soil and streams.
But other factors are also important
Rising carbon dioxide levels from climate change may allow 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 affecting other factors that are critical to plant growth, such as nutrients, temperature and water.
Nitrogen limitation
researchers think studied Between 1980 and 2017, hundreds of plants found that most unfertilized terrestrial ecosystems were becoming starved of nutrients, especially nitrogen. They attribute this nutrient loss to global changes, including rising temperatures and carbon dioxide levels.
Nitrogen is the most abundant element on Earth, making up about 80% of the atmosphere. It is an essential element in DNA and RNA, and plants need it to make carbohydrates and proteins for growth. However, plants cannot use the nitrogen gas found in the atmosphere because it has two nitrogen atoms triplet bound together so tightly that it is difficult to break down into a form that plants can use. Lightning has enough energy to break triple bonds, a process called nitrogen fixation. Nitrogen is also fixed in industrial processes that produce fertilizers.
Nitrogen-fixing nodules. Photo: Sly Tiger
But most nitrogen fixation occurs in the soil, where certain kinds of bacteria attach to the roots of plants, such as legumes. Bacteria take carbon from plants and fix nitrogen in a symbiotic exchange, combining it with oxygen or hydrogen into compounds that plants can use.
Kevin GriffinThe ratio between carbon and nitrogen in most living things is relatively fixed, explained a professor in Columbia University’s Department of Ecology, Evolution and Environmental Biology and the Lamont-Doherty Earth Observatory. This means that if plants take in more carbon dioxide to make carbohydrates, since there is more carbon dioxide in the atmosphere, nitrogen levels in the leaves may be diluted, and plant productivity depends on having enough nitrogen. “If you add carbon dioxide around a leaf, around a plant, or around a forest, usually productivity increases,” he said. “However, whether productivity gains are sustained and lasting may depend on whether you have [enough] nitrogen. Therefore, if nitrogen is limited, it may be that the plants cannot use the extra carbon dioxide and their productivity gains may be short-lived. “
Trees currently absorb about a third of anthropogenic carbon dioxide emissions, but their ability to continue doing so depends on how much nitrogen they can use. If nitrogen is limited, the benefits of increasing carbon dioxide will also be limited.
Earlier studies of nitrogen fixation, based on measurements of free-living bacteria, had predicted that the nitrogen fixation process would proceed most rapidly at 25°C, and that the rate of nitrogen fixation would decrease as the temperature rose above 25°C. In a warming world, this would mean a runaway situation where nitrogen fixation decreases as temperatures rise, leading to lower plant productivity. Plants would then remove less carbon dioxide from the atmosphere, which would lead to further warming and less nitrogen fixation, and so on. Griffin and his colleagues developed an instrument that allowed them to measure the temperature response of nitrogen to bacteria that form associations with plant roots, rather than free-living bacteria.
“We used our new instrument to look at whole-plant symbiosis in temperate and tropical trees and found that the optimum temperature for nitrogen fixation is actually about 5°C higher than any previous estimate, and in some cases up to 11°C °C Higher. This needs to be tested on a large number of plants, but if it holds, it means that nitrogen fixation is much less likely than we thought, meaning plants can remain more productive and prevent runaway situations. “
temperature rise
Griffin’s work also found that the temperature response of nitrogen fixation is independent of that of photosynthesis, which involves enzymes made from nitrogen. Higher temperatures make these enzymes less efficient. Rubisco, the key enzyme that helps convert carbon dioxide into carbohydrates in photosynthesis, “relaxes” as the temperature rises, and the shape of its pockets that hold the carbon dioxide becomes less precise. So one-fifth of the time, the enzyme ends up fixing oxygen instead of carbon dioxide, reducing the efficiency of photosynthesis and wasting the plant’s resources. With greater temperature increases, Rubisco can be completely inactivated. Since plants respond to nitrogen fertilization by increasing the amount of Rubisco they have and growing more, the discovery that nitrogen fixation can persist at higher temperatures than previously thought provides that it could compensate for Rubisco’s efficiency at higher temperatures possibility of decline.
Rising temperatures are also causing the growing season to become longer and warmer. Because plants will grow larger and longer, they will actually use more water, offsetting the benefits of partially closing the stomata. Contrary to what scientists thought in the past, the result would be drier soils and less runoff needed by streams and rivers. It could also lead to more local warming, as evaporation — when plants release moisture into the air — keeps the air cooler. Also, when soil is dry, plants are stressed and don’t absorb as much carbon dioxide, which can limit photosynthesis. scientists found Even if plants absorb excess carbon for photosynthesis during the rainy season, it cannot make up for the reduction in the amount of carbon dioxide absorbed in the previous dry year.
Fall Armyworm is a chronic pest of the southeastern United States. Photo: Canadian Biodiversity Information Agency
Warm winters and longer growing seasons also help with pests, pathogens, and invasive species that harm vegetation. During longer growing seasons, more generations of pests can reproduce because warmer temperatures speed up the insect life cycle and more pests and pathogens survive warmer winters.Rising temperatures are also driving away some insects Invade new territories, sometimes with devastating effects on native flora.
Higher temperatures and increased moisture also make crops more vulnerable. Weeds, many of which thrive in heat and elevated carbon dioxide, already account for about 34 percent of crop losses; insects are responsible for 18 percent and disease 16 percent. Climate change may amplify these losses.
Many crops start to experience stress at temperatures above 32° to 35°C, but this depends on crop type and water availability. Models show that every one degree increase in temperature is associated with a 3% to 7% drop in yields of some important crops such as corn and soybeans.
Soybean crops could be affected by rising temperatures. Photo: Quiet Jeff
In addition, higher temperatures speed up the life cycle of plants, so as plants mature faster, there is less time for photosynthesis, resulting in less grain and less yield.
Plants are also moving in response to warming temperatures. Species adapted to certain climatic conditions are gradually moving northward or to cooler higher altitudes. Over the past few decades, many North American factories have moved about 36 feet to high altitudes or 10.5 miles to high latitudes every 10 years. The Arctic tree line also moves northward by 131 to 164 feet per year. The new environment may be less suitable for species moving into it, as there may be less space or more competition for resources. Some species may have nowhere to go, and ultimately, some species will be disadvantaged by the change while others will benefit.
extreme weather
Climate change will bring more frequent and severe extreme weather events, including extreme precipitation, wind disturbances, heat waves and droughts. Extreme precipitation events can disrupt plant growth, especially in recently burned forests, and make plants more vulnerable to flooding and soil erosion. More frequent high winds can stress trees.
Climate change is also expected to bring more Combined heatwave and drought, which may negate any benefit from the carbon fertilization effect. While crop yields often decline during hot growing seasons, the combination of heat and drought could lead to a 20 percent drop in corn yields in parts of the United States and 40 percent in Eastern Europe and southeastern Africa. Additionally, a combination of heat and water scarcity could reduce crop yields in places like the northern U.S., Canada and Ukraine, which are expected to increase due to warmer temperatures.
Other Effects of Increased Carbon Dioxide
While some crop yields may increase, rising carbon dioxide levels can affect the levels of important nutrients in crops.Protein concentrations in wheat, rice and barley, and potato tubers were a study. Crops also lose important minerals including calcium, magnesium, phosphorus, iron and zinc.One Learning in 2018 of rice varieties found that while elevated CO2 increased vitamin E, it resulted in a decrease in vitamins B1, B2, B5, and B9.
Soils may store less carbon as plants absorb more nutrients from the ground. Photo: CupcakePerson13
And, counterintuitively, increased carbon dioxide-fueled plant growth may lead to reduced carbon storage in soils. Recent studies It was found that plants had to absorb more nutrients from the soil to keep up with the additional growth triggered by carbon fertilization. This stimulates microbial activity, which eventually releases carbon dioxide into the atmosphere that might otherwise remain in the soil. The findings challenge the long-held belief that as carbon dioxide increases, plants grow more, the extra biomass is converted into organic matter, and soils can increase their carbon storage.
Plants face an uncertain future
Many studies of plant life’s response to climate change seem to suggest that most plants will be more stressed and less productive in the future. However, in the face of climate change, many unknowns remain about how the complex interplay between plant physiology and behavior, resource availability and utilization, changes in plant communities, and other factors will affect plant life as a whole.
