The levels of CO2 in the atmosphere is increasing and have done so for many years. Shouldn’t this have a positive impact on plants etc.?
Maybe not nature including humans, but plants should thrive, right?
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At its simplest, the increased CO2 increases the greenhouse effect, raising overall temperatures and thus changing the climate.
This is bad for some plants, as the temperature and rainfall changes from what they need to something different.
It’s also bad for the animal life that most plants rely on. Many plants require certain insects/animals for pollination, seed dispersal etc. If the environmental changes affect the animals, they in turn effect the plants.
Yes, high CO2 levels can promote plant growth so all things being equal it would likely be good. However, all things AREN’T equal. Plants are adapted to their local climate so as climate changes some may not be able to keep up. Of course others that are more adapted will likely replace them and thrive.
The speed that the CO2 levels are rising at the moment is faster than in history, except for extinction events like mass volcanic eruptions 100s of millions years go. Natural selection can not keep up with the change in environment so they die out. If it was increased over millions of years, it would be great for plants and phytoplankton. But we are doing in 200 years.
Ecosystems are very complex, so it’s very difficult to predict the effect a change will have. The research that’s been done on this topic tells us that yes, higher levels of CO2 increase plant efficiency and water retention, but there are many other factors to take into account. For example, warming temperatures mean drier conditions, more forest fires. Another example: higher temperatures can effect the timing of pollinators like bees, increase disease, and reduce their habitat by killing them outright.
Here’s a good [summary](https://news.climate.columbia.edu/2022/01/27/how-climate-change-will-affect-plants/) of the current understanding.
It is, like sunlight or nitrogen in the ground are good too, but if rain patterns go crazy, the ecosystems of the planet would change in size and distribution and many would disappear irreversibly.
1. The rate of increase is extremely fast because its being induced by a non-natural process
2. Increased CO2 will lead to increased warming, which will **greatly** increase drought frequency and severity
3. Heatwaves will also be more extreme and more frequent
If, hypothetically, CO2 increased at a slow rate while also keeping the temperature the same due to some type of hidden variable such that heatwave + drought severity and frequency would not increase, then I think it would have a higher chance at benefitting nature.
When people say the planet is doomed because of greenhouse gasses and such, they’re not saying that Earth will become a barren wasteland devoid of life.
Life will survive. It’s just that the *current* ecosystem will be destroyed, to be replaced with something new.
When greenhouse gasses warm up the atmosphere, they end up warming the oceans too. Air and water currents dictate a lot of the factors that goes into a region’s climate. When the air and water are warmed, that will change those currents and will end up changing the local climate all over the planet. The plants and animals that live in those areas will need to adapt to new conditions, or they’ll simply die off.
Other plants and animals will show up and adapt into that ecological niche, but that doesn’t change the fact that hot areas will become hotter, wet areas will become dryer, dry areas may become wetter… it’d be catastrophic for the life that currently lives here.
The thing to wrap your head around is that “nature” isn’t just one thing. Even if some plants can take advantage of some of the aspects of climate change, the ecosystems of the world are not made of just those plants, and even they may rely on other organisms that could go extinct through climate change. And then you can get something called a “trophic cascade” which is really bad.
The best example is the classic one of Yellowstone wolves and deer. When the wolves of Yellowstone got hunted to near extinction, it was “positive” for the deer. There were fewer predators, and so more deer could exist. Except, the “good” thing for the deer meant that there were more deer, and the same amount of plants for the deer to eat. So the grasses in the park got destroyed, and the deer moved to other places, places originally inhabited by other animals, and they ate all the grass there too. Eventually there’s no grass left for anything else, the river causes excess erosion and flooding on this now barren land, and even the deer start dying due to sickness and starvation because they were overpopulated.
Higher CO2 levels will result in faster plant growth if everything else is the same and there is enough of everything else a plane needs. CO2 is sometimes added to greenhouses for exactly this reason.
The problem is in nature nitrogen is often the limiting factor, not CO2. This means any effect is often very limited, In the case of agriculture we add nitrogen in the fertilized so it is not the limit.
But even in the case of agriculture increase in the atmosphere’s CO2 level will likly have a negative effect, it increases the temperature and is not the best for planes. There will also be more locations with drought and at the same time more large storms that cause flooding.
So because more CO2 in the atmosphere has other effects and it is often not the liming factor the result in in most locations is a net negative.
I think most people have touched on the greenhouse gas effects, but CO2 also plays an important role in ocean acidification. The higher the CO2 content in air, the more acidic water exposed to that air will be. What this means for life, is any ocean organisms with shells (thing corals, some plankton, etc.) will die off, because their shells will dissolve (greatly oversimplifying the process, but that’s the end result). This then has a runaway effect where ocean organisms start to die off that produce most of the oxygen on earth, which then leads to mass extinction of land plants and animals as well.
This same effect of acidification is relevant not just to the ocean but to most life, as life has currently adapted to a specific CO2 content (and therefore a specific blood/internal fluids pH (acidity), so shifting that equilibrium faster than life can evolve leads to mass die offs.
In reality there’s no one single reason why increasing CO2 is bad, it’s a web of interconnected factors that can all be summed up as: life evolved to fit in with a CO2 concentration that is relatively steady (over thousands of years), and can’t adapt fast enough when humans start rapidly affecting the atmospheric CO2 concentration.
Edit: I saw in one of your other comments asking about what if oxygen increased instead. This would also be problematic for different reasons, as some organisms could take advantage of it more than others (think algae blooms). Also, life has evolved mechanisms to prevent damage due to oxidation, so increasing oxygen results in more oxidative stress/damage. The overall conclusion is that changing anything from the way it is now will be bad for currently living things, but if it’s done gradually enough (over millions of years), new organisms which have adapted to the changes conditions will flourish.
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