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
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.
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