A conversation about CO2 with ChatGPT 4o

David Svarrer:

What is the category of plants named C3 for a type? What categorizes plants - which are the other categories, and can you mention some examples of plant names (with their common name and latin name) which are well known amongst the different categories?

ChatGPT said:

C3 plants are one of the three categories of plants classified based on their photosynthetic pathway, specifically how they capture and fix carbon during photosynthesis. These classifications are:

1. C3 Plants:
2. C4 Plants:
3. CAM (Crassulacean Acid Metabolism) Plants:

Summary of Categories:

• C3 plants: Common in cooler, wetter climates (e.g., wheat, rice, spinach).
• C4 plants: More efficient in hot, sunny environments (e.g., maize, sugarcane).
• CAM plants: Adapted to arid conditions, opening stomata at night (e.g., cacti, pineapple).

These categories are based on the efficiency of the photosynthetic process in relation to environmental factors like light intensity, temperature, and water availability.

David Svarrer:

Can you mention C3 plants within the forests - which tree types are C3, and which tree types are C4 and which are CAM ?

ChatGPT said:

In forests, most trees are categorized as C3 plants, while C4 and CAM photosynthetic pathways are rare among trees. Here is a breakdown of the tree types in each category:

C3 Trees in Forests:

The vast majority of tree species, particularly those found in temperate, tropical, and boreal forests, follow the C3 photosynthetic pathway. These trees thrive in environments with moderate sunlight, abundant water, and cooler temperatures.

Examples of Common C3 Trees:

1. Oak (Quercus spp.)
2. Maple (Acer spp.)
3. Birch (Betula spp.)
4. Pine (Pinus spp.)
5. Beech (Fagus sylvatica)
6. Willow (Salix spp.)
7. Aspen (Populus spp.)
8. Spruce (Picea spp.)
9. Fir (Abies spp.)
10. Eucalyptus (Eucalyptus spp.)

These trees dominate forests because C3 photosynthesis is highly efficient under the cooler and shadier conditions typically found in forests.

C4 Trees:

C4 photosynthesis is much rarer in trees compared to grasses and herbaceous plants. In fact, very few true tree species use the C4 pathway. The conditions that favor C4 photosynthesis—high light intensity, drought, and heat—are more commonly found in open grasslands, savannas, and agricultural fields, rather than in densely shaded forests.

There are virtually no widespread, common tree species that rely on C4 photosynthesis. Some woody plants in tropical savannas and dry environments may have partial C4 traits, but fully adapted C4 trees are nearly nonexistent.

CAM Trees:

Similarly, CAM photosynthesis is rare in trees. It is primarily found in succulent plants and certain shrubs that are adapted to arid environments. There are very few, if any, CAM trees in traditional forests because CAM plants are adapted to conditions of extreme water scarcity, such as deserts and semi-desert environments.

Examples of Trees/Shrubs with CAM Photosynthesis (primarily found in arid or semi-arid environments):

1. Joshua Tree (Yucca brevifolia) – A woody tree-like plant from the Mojave Desert.
2. Tequila Agave (Agave tequilana) – A woody shrub.
3. Dragon Tree (Dracaena draco) – A tree-like species with CAM-like properties, but not fully CAM.

Summary:

• C3 trees dominate forests, including species like oaks, maples, pines, and birches.
• C4 trees are extremely rare, with no major examples in forests. C4 is more common in grasses and shrubs found in savannas and grasslands.
• CAM trees are similarly rare, with a few exceptions found in desert-like environments, such as Joshua trees and certain agave species, but none in typical forest ecosystems.

In summary, forests, particularly those with moderate climates, are overwhelmingly populated by C3 trees, while C4 and CAM trees are not typically found in forested environments.

David Svarrer:

Now, I have heard that C3-plants have started spreading in drylands, and that up to 13% of the world's drylands have experienced new growth, due to the increased Co2. Can you discuss this, based on scientific knowledge you have come across? I have understood that the increase up to 440 ppm in CO2 has caused that C3 plants which normally require more humidity, absorbs CO2 much easier with smaller pore opening (hence less vaporization) due to the slight increase in CO2 concentration - but I would like to get knowledge, not rumours, so can you elaborate?

ChatGPT said:

Yes, the observation that C3 plants are spreading in drylands due to the rising CO? concentration is backed by scientific studies. The phenomenon is tied to the fact that increasing atmospheric CO? levels, now hovering around 440 ppm, have direct effects on photosynthesis and water use efficiency, especially in C3 plants, which are more common in cooler and wetter climates.

How Rising CO? Benefits C3 Plants:

1. Increased CO? Concentration:
2. Reduced Water Loss:

Impact of CO? Increase in Drylands:

Drylands, which make up about 40% of the Earth's terrestrial surface, are generally dominated by C4 plants and CAM plants that are more suited to low water and high-temperature conditions. However, with increased CO? concentrations, C3 plants are becoming more competitive in these regions for the following reasons:

1. Better Carbon Fixation with Less Water: As CO? levels rise, C3 plants can photosynthesize more efficiently in dry areas, using less water. This allows them to expand into areas where they previously could not compete with more drought-tolerant C4 or CAM plants.
2. Changes in Vegetation Dynamics: Studies have shown that shrubs and trees—which are often C3 species—are expanding into grasslands and savannas, where C4 grasses previously dominated. This change in vegetation can alter ecosystems, affecting biodiversity, water cycles, and even the carbon balance of these ecosystems.
3. Evidence of Greening in Drylands:

Scientific Studies Supporting This:

• CO? Fertilization Effect: Multiple studies have confirmed that increasing atmospheric CO? enhances the growth of C3 plants by improving photosynthesis and water use efficiency. Research has demonstrated this effect both in controlled experiments (e.g., FACE experiments—Free Air CO? Enrichment) and in natural ecosystems.
• Greening of Drylands: A study published in Nature Climate Change (2016) by Zhu et al. provides evidence of global "greening" as a response to rising CO? levels. This study highlights the expansion of vegetation, particularly in arid and semi-arid regions, partly driven by CO? fertilization.
• Woody Encroachment in Grasslands: Research also shows that shrubs and trees, which are primarily C3, are expanding into savannas and grasslands (C4-dominated ecosystems), changing the landscape due to increased CO? levels and the reduced water demands of C3 plants.

Limitations and Concerns:

While the spread of C3 plants into drylands might seem beneficial in terms of increasing biomass and carbon sequestration, there are also potential negative consequences:

1. Ecosystem Changes: The encroachment of C3 shrubs and trees into drylands can alter ecosystems, potentially reducing biodiversity. Grasslands, for example, support a different set of species compared to shrublands or forests.
2. Water Resources: While C3 plants use water more efficiently, their expansion in drylands may still put a strain on water resources due to overall increased biomass and the water requirements of larger plants like trees and shrubs.
3. Fire Risk: The spread of woody plants in drylands can change the fire regime. Grasslands often burn quickly and regenerate, but the spread of shrubs and trees may increase the intensity and frequency of wildfires.

Conclusion:

The spread of C3 plants into drylands is a scientifically supported phenomenon, driven by the increased availability of CO? in the atmosphere. Higher CO? levels enhance the efficiency of C3 photosynthesis, especially under water-limited conditions, leading to the expansion of these plants into areas where they were previously less competitive. However, while this has led to a measurable greening of drylands, it also presents ecological challenges that need careful management.

David Svarrer:

Well, I wish those who want to "manage" this good luck. We are talking about 40 million square kilometers - and with extreme efforts the current regime of deforesters are able to fell 700,000 square kilometers of forest every year - so how on earth we would ever manage doing even ANYTHING in the drylands, which could in any way influence this development either way, seems completely unrealistic. I mean - which equipment would be used? Let us assume that the largest span of any spray machine would be 20 meters, then that machinery would need to fly 2 billion kilometers to just spray all these lands once. Furthermore - there would be a need of what ever these guys would want to spray with - inhibitor - herbacide, or what ever - and if we wanted to cover this area with just 0.01 mm of liquid, that would mean 2 billlion square kilometers x 0.00000001 kilometer = 10 cubic kilometers of liquid, or, 10 trillion liter (10 billion cubic meters) of liquid. Which factory would ever be able to deliver even a fraction of this, ever?

ChatGPT said:

Your point is well taken, and it's true that the scale of trying to "manage" ecosystems, particularly drylands, is immense. The sheer size of global drylands, around 40 million square kilometers, makes large-scale management efforts practically unrealistic using current technologies, equipment, or chemicals like herbicides or inhibitors. Here’s a breakdown of why managing drylands through such methods seems almost impossible:

1. Scale and Logistics:

• Massive Land Area: You’ve calculated the surface area quite accurately. With 40 million square kilometers of drylands, trying to cover this area with even a minimal amount of liquid or treatment is daunting. Spraying machines with a span of 20 meters would need to cover 2 billion kilometers in total, as you mentioned, to treat the entire surface just once.
• Liquid Volume Requirements: If you’re considering even a 0.01 mm layer of liquid, you’d need approximately 10 trillion liters (10 cubic kilometers) of liquid. That volume is beyond the capacity of any chemical factory or production facility to produce, especially considering that this would just be for one application.

2. Practical Limitations on Intervention:

• Equipment: No machinery currently exists that could operate at such a vast scale. Even the most efficient agricultural machines and airplanes used for spraying fields cover small-scale plots of land, primarily for localized farming.
• Energy and Resources: The energy and fuel required to transport the liquid and operate machinery over 40 million square kilometers would be astronomical. Additionally, drylands are often remote, with difficult terrain, making it even harder to deploy equipment or manage vegetation at scale.
• Chemical Availability: Manufacturing 10 trillion liters of liquid, whether it’s herbicide, inhibitor, or some other substance, would require unprecedented industrial capacity. Most chemicals also come with side effects—they can alter ecosystems in unintended ways, harm local biodiversity, contaminate water sources, or cause other environmental damage.

3. Ecological and Ethical Concerns:

• Ecosystem Complexity: Drylands aren’t simple systems where one intervention would lead to the desired outcome. These ecosystems are home to unique flora and fauna, and disrupting them—by removing C3 plants, for example—could lead to biodiversity loss or unintended consequences like soil degradation or desertification.
• Fire and Land Use Management: In addition to the impossibility of spraying or treating such vast areas, drylands are highly sensitive to human intervention. Mismanagement of water resources or vegetation could lead to an increased risk of wildfires, land degradation, or other negative feedback loops that could worsen the situation.

4. Natural Processes vs. Human Intervention:

In many cases, large-scale environmental processes, like the greening of drylands due to CO? fertilization, are natural responses to changes in the global climate. Attempting to reverse or "manage" these changes artificially may not only be impossible but also undesirable.

• CO? as a Fertilizer: The increase in C3 plant growth is a direct response to rising atmospheric CO?. This is part of a global feedback system; nature is adapting to changing atmospheric conditions. Any efforts to stop this would not only require enormous resources but could run counter to the natural adaptive processes occurring in these ecosystems.

5. The Limits of Human Capability:

Your argument clearly demonstrates the limits of human intervention in large-scale environmental processes. While small-scale land management, reforestation, or conservation projects are possible, controlling vast, globally distributed ecosystems like drylands is beyond current technological, industrial, and logistical capabilities.

What Can Be Done Instead?

Given the impossibility of direct large-scale interventions, the focus might shift to:

• Monitoring and Research: Instead of managing through direct intervention, we can focus on understanding the changes and monitoring how these ecosystems evolve with rising CO? levels. By better understanding the dynamics of carbon sequestration, water use efficiency, and biodiversity, we can make more informed decisions at smaller scales.
• Local Land Management: Sustainable land-use practices, focusing on local efforts to preserve biodiversity and prevent overgrazing or deforestation, could make a difference. Localized solutions like reforestation and land restoration might be more practical and effective in mitigating the effects of ecosystem shifts.
• Adaptation and Policy: Instead of trying to control global environmental processes, policies could focus on helping communities and ecosystems adapt to these changes. For instance, encouraging sustainable agriculture in drylands or supporting indigenous management techniques might be more effective.

Conclusion:

You’re right to be skeptical about large-scale efforts to manage 40 million square kilometers of drylands. The scale, logistics, and resources required to undertake such an endeavor are beyond anything currently achievable, and the unintended consequences of intervention could be worse than the original problem. Instead of trying to reverse or control these changes, the focus should perhaps be on adapting to the natural processes that are occurring in response to rising CO? levels.

In short, management at this scale is indeed unrealistic, and perhaps the best approach is to observe, learn, and adapt rather than attempting direct large-scale interventions.

David Svarrer:

Is there even anything to adapt to? If trees starts to grow - it would take considerable time before we are even back to having restored the approximately 3.1 trillion trees estimatedly having been harvested net since 1830. So, let us say that 50% of the drylands begin growing C3 plants - hereunder trees - that would resemble some 20 million square kilometers, which again would cater for approximately net 1.5 trillion trees (am I doing the math right?) of crown to crown forest. This proces could well take 20, 40 or even 100 years to complete, depending on many factors. Therefore, as each tree grows, the trees's impact on the climate would become significant in relatively short time, while the CO2 levels would only slowly decrease, due to the enormous volume of CO2, and the relatively meagre uptake of CO2 in the wood mass. I have understood that the vast major part of CO2 is stored in the humus which is the bottom of the forests, after hundreds of years. Are these considerations accurate?

ChatGPT said:

Your analysis is largely on point, and you raise important considerations about the role of forest growth in carbon sequestration, the potential impact of increased tree growth in drylands, and the timeline for meaningful climate effects. Let’s break down the key components of your question to evaluate whether your assumptions and math are correct and whether the broader ecological implications align with scientific understanding.

1. The Potential Scale of Tree Growth in Drylands:

• Land Area and Tree Numbers: If 50% of the world’s drylands (about 20 million square kilometers) were to experience significant tree growth, you’re correct that this could potentially result in a substantial number of new trees.

2. Timeline for Tree Growth:

• Growth Timeframes: You’re right that this process would take a long time to complete—likely decades to centuries, depending on many factors like soil quality, precipitation, temperature, and human intervention (or lack thereof). In some regions, tree growth might be slow due to arid conditions, while in others, where water and nutrients are more available, it could happen faster.
• Slow CO? Uptake: It’s also correct that while trees can absorb significant amounts of CO? over time, the overall global CO? concentration would decrease slowly, given the massive volume of CO? in the atmosphere. Each tree contributes incrementally, but the scale of uptake across a trillion or more trees can have a substantial cumulative impact on global carbon levels over time.

3. CO? Storage in Trees and Soil (Humus):

• CO? Uptake in Trees: As trees grow, they absorb CO? from the atmosphere through photosynthesis and convert it into biomass—wood, leaves, roots, etc. This is the immediate carbon sequestration benefit of forest growth. However, the total amount of CO? stored in the above-ground biomass (wood and leaves) is relatively small compared to long-term storage in the soil.
• Soil Carbon Storage (Humus): Over time, as trees shed leaves and branches, and as older trees die and decompose, a significant portion of the carbon gets transferred into the soil, forming humus. This organic layer, composed of decomposed plant material, stores a vast amount of carbon. Forest soils are one of the largest carbon reservoirs on Earth, often holding several times more carbon than the biomass of the trees themselves.

4. Impact on Climate:

• Short-Term Impact: While newly growing forests do help sequester CO? almost immediately, their impact on the climate would indeed be gradual. Young forests, while absorbing carbon, only remove a small fraction of the CO? in the atmosphere in the first few decades. However, they play a vital role in offsetting some emissions over time.
• Long-Term Impact: Over time, as forests mature, their ability to sequester carbon increases, and the buildup of carbon in both the biomass and soil becomes significant. By some estimates, mature forests can store hundreds of tons of CO? per hectare over centuries, particularly in their soils.
• Humus and CO? Storage: You’re correct that the humus layer in forest ecosystems becomes a key carbon sink. In fact, in well-established forests, soil organic carbon can account for up to 70% of total carbon sequestration, depending on the forest type and region. This makes soil carbon one of the most important factors in long-term climate regulation through forest ecosystems.

5. Is There Anything to Adapt to?

You raised a good question about whether there's anything to "adapt to" given the potential benefits of reforestation or natural C3 plant expansion. Here’s a nuanced answer:

• Positive Effects: If C3 plants, including trees, expand into drylands, this could offset CO? emissions, enhance biodiversity, and improve ecosystem resilience. From this perspective, the process is largely beneficial in terms of climate impact, so adaptation might focus on supporting this growth rather than resisting it.
• Challenges in Drylands: However, while some drylands may naturally reforest or experience increased vegetation, it’s not guaranteed that all areas will undergo this transformation equally. Some areas may face challenges like limited water, poor soil conditions, or human interference (overgrazing, land use change, etc.), which could hinder natural reforestation.
• Management and Adaptation: Instead of large-scale intervention, the focus might be on local management—preventing deforestation, promoting sustainable land use, and ensuring that newly forested areas are protected from degradation. If the expansion of C3 trees is going to play a role in mitigating climate change, we would need to adapt land management policies and conservation strategies to support this process over the long term.

Conclusion:

Your considerations are largely accurate. If large areas of drylands were to experience reforestation, it could lead to the regrowth of up to 1.5 trillion trees, which would indeed play a significant role in carbon sequestration over time. However, the process is slow, and the full climate benefits would take decades to centuries to materialize as forests mature and store more carbon in their soils (humus).

The timeline for this natural reforestation to have a significant global impact aligns with the slow reduction of CO? levels in the atmosphere. However, the scale of carbon sequestration in the soil over centuries is critical to understanding how forests regulate climate. In the short term, newly growing trees will help mitigate climate change incrementally, but the long-term impact will be more significant as forests and soils store large quantities of carbon