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.
Nitrogen limitations
Researchers that studied hundreds of plant species between 1980 and 2017 found that most unfertilized terrestrial ecosystems are becoming deficient in nutrients, particularly nitrogen. They attributed this decrease in nutrients to global changes, including rising temperatures and CO2 levels.
Nitrogen is the most abundant element on Earth, making up about 80 percent of the atmosphere. It is an essential element in DNA and RNA and is needed by plants to make carbohydrates and proteins for growth. However, plants cannot use the nitrogen gas found in the atmosphere because it has two atoms of nitrogen triply bonded together so tightly that they are difficult to break apart into a form plants can use. Lightning has enough energy to break the triple bond, a process called nitrogen fixation. Nitrogen is also fixed in the industrial process that produces fertilizer.
But most nitrogen fixation occurs in the soil, where certain kinds of bacteria attach to the roots of plants, such as legumes. The bacteria get carbon from the plant and in a symbiotic exchange, fix the nitrogen, combining it with oxygen or hydrogen into compounds plants can use.
Kevin Griffin, a professor in Columbia University’s Department of Ecology, Evolution and Environmental Biology and the Lamont-Doherty Earth Observatory, explained that most living things have a relatively fixed ratio between carbon and nitrogen. This means that if plants take up more CO2 to create carbohydrates because there’s more CO2 in the atmosphere, the amount of nitrogen in the leaves may be diluted, and a plant’s productivity depends on having enough nitrogen. “If you increase the CO2 around a leaf or around the plant or around the plot of forest, usually the productivity goes up,” he said. “But whether or not that increase in productivity lasts and is permanent, can be a function of whether you have [enough] nitrogen. So if nitrogen is limited, it could be that a plant just cannot use that extra CO2 and its boost in productivity can be short lived.”
Trees currently absorb about a third of human-caused CO2 emissions, but their ability to continue to do this depends on how much nitrogen is available to them. If nitrogen is limited, the benefit of increased CO2 will be limited too.
Earlier research on nitrogen fixation, based on measurements of free-living bacteria, had predicted that the fixation process works fastest at 25°C, and that as temperatures rose above 25°C, the rate of fixation would go down. In a warming world, this would have meant a runaway scenario where nitrogen fixing would decrease as temperatures rose, resulting in less plant productivity. Plants would then remove less CO2 from the atmosphere which would cause further warming and less nitrogen fixing, and so on. In a new paper, Griffin describes how he and his colleagues developed an instrument that enabled them to measure the temperature response of nitrogen on the bacteria that formed an association with the roots of plants, as opposed to on free-living bacteria.
“What we found with our new instrument looking at whole-plant symbioses in temperate and tropical trees, was that the optimal temperature for nitrogen fixation was actually about 5°C higher than any of these previous estimates, and in some cases as much as 11°C higher. This needs to be tested over a huge number of plants, but if it holds, it means that the likelihood of nitrogen fixation decreasing is much lower than we thought, which means that plants could stay more productive and prevent the runaway scenario.”
Rising temperatures
Griffin’s work also found that the temperature response of nitrogen fixation is independent from the temperature response of photosynthesis, which involves enzymes made with nitrogen. Higher temperatures can make these enzymes less efficient. Rubisco is the key enzyme that helps turn carbon dioxide into carbohydrates in photosynthesis, but as temperatures go up, it “relaxes” and the shape of its pocket that holds the CO2 gets less precise. Consequently, one fifth of the time, the enzyme winds up fixing oxygen instead of carbon dioxide, lowering the efficiency of photosynthesis and wasting the plant’s resources. With an even greater temperature increase, Rubisco can completely deactivate. Since plants respond to nitrogen fertilizer by increasing the amount of Rubisco they have and growing more, the finding that nitrogen fixation can be sustained at higher temperatures than previously thought offers the possibility that it could compensate for the decreasing efficiency of Rubisco at higher temperatures.
Rising temperatures are also causing growing seasons to become longer and warmer. Because plants will grow more and for a longer time, they will actually use more water, offsetting the benefits of partially closing their stomata. Contrary to what scientists believed in the past, the result will be drier soils and less runoff that is needed for streams and rivers. This could also lead to more local warming since evapotranspiration—when plants release moisture into the air—keeps the air cooler. In addition, when soils are dry, plants become stressed and do not absorb as much CO2, which could limit photosynthesis. Scientists found that even if plants absorbed excess carbon for photosynthesis during a wet year, the amount could not compensate for the reduced amount of CO2 absorbed during a previous dry year.
Warmer winters and a longer growing season also help the pests, pathogens, and invasive species that harm vegetation. During longer growing seasons, more generations of pests can reproduce as warmer temperatures speed up insect life cycles, and more pests and pathogens survive over warm winters. Rising temperatures are also driving some insects to invade new territories, sometimes with devastating effects for the local plants.
Higher temperatures and an increase in moisture also make crops more vulnerable. Weeds, many of which thrive in heat and elevated CO2, already cause about 34 percent of crop losses; insects cause 18 percent of losses, and disease 16 percent. Climate change will likely magnify these losses.
Many crops start to experience stress at temperatures above 32° to 35°C, although this depends on crop type and water availability. Models show that each degree of added warmth can cause a 3 to 7 percent loss in the yields of some important crops, such as corn and soybeans.
In addition, an increase in temperature speeds up the plant lifecycle so that as the plant matures more quickly, it has less time for photosynthesis, and consequently produces fewer grains and smaller yields.
Plants are also on the move in response to warming temperatures. Species that are adapted to certain climatic conditions are gradually moving north or to higher elevations where it is cooler. In the last several decades, many North American plants have moved approximately 36 feet to higher elevations or 10.5 miles to higher latitudes every 10 years. The Arctic tree line is also moving 131 to 164 feet northward towards the pole each year. New environments may be less hospitable for the species moving into them as there might be less space or more competition for resources. Some species may have nowhere left to move and ultimately, certain species will be disadvantaged by the changes while others will benefit.
Extreme weather
Climate change will bring more frequent and severe extreme weather events, including extreme precipitation, wind disturbance, heat waves, and drought. Extreme precipitation events can disturb plant growth, particularly in recently burned forests, and make plants more vulnerable to flooding and soils to erosion. More frequent high winds can stress tree stands.
Climate change is also expected to bring more combined heat waves and droughts, which would likely offset any benefits from the carbon fertilization effect. While crop yields often decrease during hot growing seasons, the combination of heat and dryness could cause maize yields to fall by 20 percent in some parts of the US, and 40 percent in Eastern Europe and southeast Africa. In addition, the combination of heat and water scarcity may reduce crop yields in places like the northern US, Canada, and Ukraine, where crop yields are projected to increase because of warmer temperatures.
Other effects of increased CO2
While some crop yields may increase, rising CO2 levels affect the level of important nutrients in crops. With elevated CO2, protein concentrations in grains of wheat, rice and barley, and in potato tubers decreased by 10 to 15 percent in one study. Crops also lose important minerals including calcium, magnesium, phosphorus, iron, and zinc. A 2018 study of rice varieties found that while elevated CO2 concentrations increased vitamin E, they resulted in decreases in vitamins B1, B2, B5 and B9.
And, counterintuitively, the CO2-fueled increase in plant growth may result in less carbon storage in soil. Recent research found that plants have to draw more nutrients from the soil to keep up with the added growth triggered by carbon fertilization. This stimulates microbial activity, which ends up releasing CO2 into the atmosphere that might otherwise have stayed in the soil. The findings challenge the long-held belief that as plants grow more due to increased CO2, the additional biomass would turn into organic matter and soils could increase their carbon storage.
Plants face an uncertain future
Many of the studies into the response of plant life to climate change seem to suggest that most plants will be more stressed and less productive in the future. But there are still many unknowns about how the complex interactions between plant physiology and behavior, resource availability and use, shifting plant communities, and other factors will affect overall plant life in the face of climate change.
Useful and accessible article; I’m using it to stimulate discussion in my undergraduate botany course
unlike sflint i found this confusing and wrong. I think global is good and we should make it happen more often then it does. Lets all tke action a=and make a better world
We all have our opinions. If you find it wrong, then you find it wrong. But this is a credible source. It is 99.99% right.
P.S. I only say 99.99% because nobody is 100% right.
Eco-evolutionary spatiotemporal scales, and their gradients, are going to be key. That is to say, in the real context of intense human development pressure that broadly threatens habitat and biodiversity, the destabilization and fragmentation of habitat has the potential to threaten plant communities, in combination with the background environmental changes related to climate change. It seems to me that in general, increased CO2 is going to help plants cope with elevated temperatures and water stresses; thus, my feelings are that large scale ecological conservation and recovery and the reversal of fragmentation and destructive human development patterns are increasingly important to provide ecological communities the stability – such as microclimate, needed to adapt to broader changes, and that most attention or resources should be spent reversing destructive human development which is the more direct threat. That’s also to say larger scale healthy ecoystems are more self-sustaining and will be resilient, and we should spend time and effort assisting their recovery in anticipation of potential stresses related to climate change.
Fascinating and a perfect example of benefits vs. harms. I am using this in a module on photosynthesis designed for adult learners. Thank you!
Nice piece of blog.
There is a clear connection of man with nature. Man seems to be abusing this connection for his selfish needs.
You mean by growing from 1 to 8 billion people and rising. Are you repronouncing that whopping change to selfish abuse? You are here. Who exactly are you including in this sweeping comment. Everybody else but you?
I agree. When people say “man” does this or that, it means “the other guy” does it.
So you acknowledge you’re abusing this connection for YOUR selfish needs Noah. I agree, you are, we all are. It’s called survival and improvement Noah. If you don’t like it you know what to do to reduce the population.
More CO2 does the same thing in nutrient quality as more H2O does. It makes yields more abundant. And nutrient quality more dilute. What to do? As crop and soil sciences have known for decades, bring up soil fertility to balanced levels. That is important for agriculture, the part of the environment that moves nutrients into food and out of food producing areas. For the environment, those nutrients aren’t going anywhere.
Either way the earth is about 5 percent greener than it was 20 years ago.
As a student in earth and environmental science, I find this article helpful for the current curriculum. I learned a lot about climate change, and how plants can react to it.
The unanswered question in this article is ‘ What was his baseline for comparison?’
Its all very well saying yes many if not most plants will grow better and potentially faster, and balancing this positive against negatives like greater fertility and/or water requirements but this has been the case with all developments and improvements in crop varieties. More production always requires more input. Further big strawberries never taste as good or sweet as small ones, ie flavour and sugar gets diluted with increasing fruit size.
But back to the baseline, what ever it is, what were crop yields like at only 280 ppm CO2. History records cold years without “summers” , failed crops and widespread famine. If it were possible to somehow return to 280 ppm CO2 would our modern crops actually produce anywhere near as much as they do. I seem to recall that some commercial greenhouses add CO2 to achieve atmospheric rates of up to 1000 ppm CO2
I find this article helpful. I see what global warming will do to our planet. It’s time to take a stand! We need to drop our CO2 levels. #GOGREEN!
A typical Phanerozoic CO2 level was about 1500 PPM and was as high as 7000 PPM. 500 million years ago.
At 150 PPM of CO2 plants will die.
As for global warming, it has been going on for hundreds of years. Greenland was once green and may be once again following the “little ice age.”
Maybe Russia will become more hospitable.
What’s the problem?
If any, it would be the slow depletion of oxygen in the atmosphere.
Just accept the sky is falling. I haven’t time to explain…
I am not a scientist but one thing is abundantly clear to me , there’s more that we don’t know than there is what we do. That doesn’t mean the pursuit of knowledge is wrong , i would argue the contrary , we should pursue the truth and acknowledge it heartily when it presents itself.
I found this an Interesting article , there did however seem to me that it is influenced by the politicization of this topic, we have had many doomsayers over the past years from a coming Ice age to world food shortages and my concern is that the politicization of this is being used primarily for political ends IE: there’s lots of action and posturing but little real progress , its more about optics than substance , if we were really serious we would first do what is achievable like nuclear energy and LNG , but the all or nothing mentality i currently see with the environmental groups and their dystopian views is more dangerous in my opinion than anything else.
I agree.
Pursuit of knowledge is natural. Pursuit of agendas is destructive.
I am no scientist and would like to understand:
How mining of rare earth in order to cover land with solar panels to generate energy (with intense heat as a byproduct) aligns with global warming mitigation?
How does this compare to plants which absorb heat, cool the earth, store energy, provide nutrients to soil and living creatures, and are naturally occurring and self-sustaining with the ability to naturally evolve and adapt to the environment?
Is the vilification of nuclear power and carbon based energy politically (profit) driven or scientifically based?
Is there an unbiased study that shows how solar power with battery storage helps the climate and the ecological balance on earth?
How do obsolete solar panels and spent batteries polluting our earth compare to nuclear waste or elevated C02 in our atmosphere?
Can the plants that sustain our food supply, supply oxygen and cool our planet repair the damage done to the earth in support of solar energy like it can mitigate carbon in the atmosphere and maintain the life sustaining balance experienced on earth for millenniums?
We have seen plants thrive naturally at locations impacted by nuclear catastrophes. Is the same true for exhausted lithium mines, and battery and solar panel landfills? How does it compare to uranium mines? Is there a cost comparison on repairing these sites?
How much pollution is generated by mining, manufacturing, using and disposing of the current energy technologies being pushed to combat climate change compared to nuclear and carbon energy?
Does globalization help the environment or just the institutions that profit from it?
How does local production broadly across all goods and products compare to the costs to build, maintain and power global supply chains?
Is data and science unbiased when funding is agenda driven?
Is there a correlation between hysteria and fact? Harmony and hype?
Many of my same thoughts & questions but you articulated them very well. Additionally all that lithium is mined with child labor. Also, where & how are all those old solar panels & steel wind turbines being repurposed/ recycled??
Will running an electrical current in the soil promote nitrogen fixation?
You would most likely just change the soil composition by reducing and oxidizing various species in a manner that would be very difficult to predict, creating a hell of a grog. It would mess with pH and ionic concentrations and stuff I believe. To break a nitrogen-nitrogen triple bond, you would need an actual spark, lightning, to break it 🙂
Nice documentation. I really needed this kind of content. Thanks to the publisher of this amazing and interesting writing.
I think the fertilizing effect of increased CO2 far more that outweighs any concern with the heat impact that it is causing. Thank you for this article that documents its increased fertilizer value. My understanding is that CO2 has been reduced in the atmosphere over the last 2 million years due to the utilization of CaCO2 for sea shell formation which is then sequested in the crust of the earth. Would appreciate your thoughts in this regard.
As I understand it, the trend of reduction in CO2 levels in the atmosphere has been going on for about 520 million years. Which is roughly the time where sea life developed shells.
Carbon and other Green House Gases can be captured and put directly into the soil …see how this is being done in Africa with the help of the diesel tractor and how these African farmers do not use any fertilizer https://www.carbon-farmer.com/ Please do not simply dismiss the use of the diesel. Stop and think how Carbon Capture Utilization and Storage technology is becoming more and more available and economically feasible and abating the use of Diesel and other fossil fuel and to abate industries. The key word here is “ABATE”. Do not confuse the prohibition of non-ABATED fossil fuel with the use of ABATED fossil fuel. There is a huge difference. Plus think about and criticize how the minerals needed for batteries to electrify everything is causing soil degradation in a lot of places and how sand needed for glass to make solar panels and cellphones is causing sand mining to get out of control. https://youtu.be/5jyMTf3azfk?si=c_-s-TrX8dvmaVUA
Very Good Article Contains very good information
I find this to be a very interesting topic and I don’t claim to be a scientist, but everything on this earth shares in a balancing act. I didn’t read anywhere in the article about solar flares, volcanic activity, and an endless number of environmental events that contribute to the overall health of the planet. I agree with a lot of the those who commented that this is more of a political or economic driven issue than a true scientific based agenda!!
The earth was a lot warmer a thousand/million plus years ago and still coming out of the little ice age just about 500 to 600 years ago. It is just trying to get back to those days and nothing man does will stop it. Climate isn’t static. It constantly changes. You can’t control Mother Nature.
All you have to do is visit a successful greenhouse and observe the elevated level of CO2 the management spends good money to maintain in order to continue making a living. This global warming thing is falling apart despite saturation support from fake news and outright censorship by big tech.