While planting (trillions of) trees could help us absorb more CO2, are there real risks to this human intervention in nature’s biodiversity? Won’t our “trees of choice” be wildly different from what would grow naturally? Can we even measure/foresee the longterm impact of planting trillions of trees ourselves?
In: Biology
In the most general sense of the word “risk”, then yes there is always a degree of risk in pretty much any activity (human or otherwise). The term “real risk” has insufficient precision to give any sort of answer but a lot of it would depend on how things were done.
Generally speaking, if it is plainly reforestation, then the most likely candidate would be some kind of local species. Of course, if the idea is to replant an area like a desert (where there might not be anything local) then the people behind it would very likely choose something that is “local enough” but still be able to grow.
There will be some consequence to this (clearly for CO2, if successful) and some might not be totally foreseeable. But then again, nothing done on a large enough scale will be without some degree of uncertainty. Still, trees don’t grow overnight and there will be a fair amount of time (decades at a minimum) to collect relevant data and adjust to the situation.
It is almost inconceivable that any effort would be so concentrated that there would be major effects. We are, as a species after all, burning down or deforesting at a huge rate today. Any sort of replanting would be spread out in many locations (that were likely forested a few centuries ago) so there would be little chance of it a huge negative consequence.
When to many trees or plant life are over reaching, it creates hyperoxia in humans and animals.
“Prolonged exposure to higher oxygen levels at atmospheric pressure can lead to pulmonary and ocular toxicity. Symptoms of oxygen toxicity may include disorientation, respiratory problems, or myopia. Prolonged exposure to higher than normal partial pressures of oxygen can result in oxidative damage to cell membranes.”
source:https://en.wikipedia.org/wiki/Hyperoxia
This is a real danger to humans, life on earth in general and the earth depopulation crowd use “green house gases, global warming”, to scare humans into to thinking that the environment needs more trees, plants.
There are certain species you are only allowed to plant in certain places to not change the ecosystems. We can totally measure the longterm impact and there is no biological or ecological risk. The only reason why we didn’t use this earlier is the money, time, and space involved.
Honestly, only in extremely large forestation projects, and it mostly has to do with water sourcing. For example, there have been theoretical plans proposed to irrigate and forest the Sahara or the Australian Outback as a way to capture carbon. In theory at least, it’s doable but where do you get the water? The Sahara sits atop an absolutely massive fresh water aquifer, and the Outback may as well (I can’t recall atm), but that wouldn’t feed the project forever. So, you probably have to do mass desalination of ocean water to “feed” the project. However, what do you do with all the salt? Do you actually reduce carbon emissions once you account for the energy used in desalination? While there’s very little native life in the Sahara (more in the Outback), it’s not zero and what happens to those species?
On the other hand, when you’re just talking about reforestation of a previously cleared area, the natural infrastructure is mostly all in place still. The theoretical problems you’re looking at mostly have to do with displaced lifeforms. Let’s say you decide to reforest an area with the same type and mix of trees that used to grow there. One of those trees needs insect species X to thrive; they have a symbiotic relationship. Insect species X was kept in check mostly by bat species Y that lived in the forest’s canopy. The insects might return nearly as soon as the trees do, but the bats probably won’t until the trees reach a height to have that canopy back, or they might have gone extinct, or need some other thing that won’t come back at all, etc.
There is a chance of it having a bad effect on global warming. Everything, including the planet as a whole, has something known as albedo which just means how much light bounces off of it. Trees have a lower albedo than sand or snow so some proposals like covering the Sahara desert with trees could actually have the effect of warming the planet further because the desert, as it is now, reflects a lot of light into space. Trees could reduce this reflection and overall warm the planet.
This is just a possibility though and climate modeling and prediction is too complex for me to give a definite answer on what would be better or worse.
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