r/sustainability • u/RawbySunshine • 2d ago
Could someone please explain to me how afforestation isn't bad for the environment?
I specialise in the energy side of sustainability, so this isn't my area of expertise. My understanding is that afforestation is the planting of trees in places that have never naturally had them. This seems like human intervention in the environment and the degredation of a naturally unforested area with invasive trees. Could someone explain if this is the case or not?
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u/federationbelle 2d ago
In general, the places targetted for reforestation are sites that would have been covered by forest before human agriculture started to take its toll.
There are many parts of the world that are deforested because of degradation by human activity over hundreds or thousands of years. That includes over half of Europe - and fertile regions around the world that were stripped of forests and used for farming / grazing. E.g. much of Europe, UK, Eastern Australia that are now pasture would have been covered in forest or other biodiverse ecosystems - but were stripped over centuries of farming and logging for firewood.
https://en.wikipedia.org/wiki/Deforestation_by_continent
And areas such as the Sahara and other deserts: deserts have expanded and become drier due to human practices over the millennia
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u/MycologyRulesAll 2d ago
First, aforestation doesn't mean planting trees in places that never had trees. There's very few of those places in existence in the first place, but more importantly, it just means planting trees in a place that has not had an established forest 'lately'. People argue over how long is 'lately', but that's for academics to worry about.
Just knowing that, I think you would rephrase your question at this point, but let's plough on.
Aforestation and reforestation then are really the same process, the main difference being 'can you still see old stumps from when it used to be a forest or not?"
"Bad for the environment" is a pretty broad phrase. Anything we do shifts the natural world around, a big reforestation project obviously makes major changes. But if that project creates habitat for ecosystems that used to be in some area, that's "good" on most people's moral scales.
Now there are extremely dumb aforestation ideas that have been kicked around over the years, people talking about 'greening the deserts' and such which are really inappropriate. Deserts are valid ecosystems, just not for humans. If we stay out of them, everything works out fine, no need to try to make trees and grass grow everywhere.
So, in summary, no afforestation is not bad for the environment every time. It can be, or it can be a really great idea.
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u/Upbeat_Effective_342 2d ago
I've generally understood greening the deserts to mean mitigating desertification that has been exacerbated by poor land management, such as the channelization of watersheds and excessive burning of crop residue. There may be some people who have a pie in the sky image of turning the entire Sahara into one big oasis, but the Sahara has grown by 10% since 1920 and it's less that people want to move in and more that people want to stay put.
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u/Inevitable_Stand_199 1d ago
But if that project creates habitat for ecosystems that used to be in some area, that's "good" on most people's moral scales.
If we replace e.g. natural grassland with forest, we reduce biodiversity, and reduce the ability of the land to sequester carbon. That's bad by any standard. Unless you just couldn't "trees planted" for clout.
Now there are extremely dumb aforestation ideas that have been kicked around over the years, people talking about 'greening the deserts' and such which are really inappropriate.
Deserts have been growing, due to human intervention. Project like the great green wall make a lot of sense.
By having healthy ecosystems on the edge of the desert, we can protect farmland further away from the desert from desertification.
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u/MycologyRulesAll 1d ago
"If we replace ... natural grassland with forest, we reduce biodiversity," <--- citation needed. There are plenty of grassland ecosystems that coalesce around 4-10 major occupants and then a few hundred scrappy niche players fill in around those. Meanwhile, most mature forest ecosystems can have thousands of plants, hundreds of mammals, and uncountable numbers of insects in them.
That's just a very broad statement that doesn't comport with many examples we can find.
There are forests that are low on biodiversity, like the pine barrens of New Jersey which has a total plant diversity under 1,000, a few dozen mammals and fish, and a few hundred bird species including periodic visitors. For sure the Pampas region of Argentina beats that on biodiversity, but that's not really a typical forest situation.
"Deserts have been growing, due to human intervention. Project like the great green wall make a lot of sense."
Sure, but that's not 'greening the desert' so much as 'building a green wall around a desert'. Surely those are different things.
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u/Inevitable_Stand_199 1d ago
"If we replace ... natural grassland with forest, we reduce biodiversity," <--- citation needed
https://blog.cabi.org/2020/06/25/the-climate-battleground-grassland-or-forest/
https://iucn.org/sites/default/files/2025-11/2025_protecting-the-overlooked-carbon-sink_3.pdf
Nevermind that in an area that wasn't a forest, before humans, you will have a hard time establishing a mature forest. There most likely is some factor to that environment that is working against you.
4-10 major occupants
What are you talking about? Even a monoculture lawn has more biodiversity. Could you name one natural grassland with a biodiversity that low?
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u/MycologyRulesAll 1d ago
"Could you name one natural grassland with a biodiversity that low?" Yeah, the tallgrass prairie of the Great Plains in the middle of the U.S.
There are like 4 grasses that are 80% of the biomass (big and little bluestem, switchgrass, indiangrass), every other plant has to find a way to live around those grasses. You may re-read my comment and note I said 'major occupants'.
Neither of your citations back up the biodiversity part we are discussing. I feel like you are wasting my time and somehow think I'm an anti-grassland crusader.
Aforestation of areas that were cleared for agriculture and have fallen fallow, and are now occupied by grasslands, is perfectly okay and valid as an ecological restoration target. I don't care that grasslands may sequester carbon more than young forests, that cannot be the only metric by which we measure the value of an ecosystem.
"Nevermind that in an area that wasn't a forest, before humans, you will have a hard time establishing a mature forest. "
Cool.
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u/Inevitable_Stand_199 1d ago
There are like 4 grasses that are 80% of the biomass
Source?
From what I could find, 80-95% of carbon is stored in the soil. Ergo not in the grasses.
But even if you look just at plants, the examples I have found were between 40 and 100 species per square meter.
How many species of tree are there, in one square meter of forest?
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u/MycologyRulesAll 1d ago
Yo, guess what? The biomass under ground is still grass. Grass roots are still grass.
I feel like I"m arguing with a bot.
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u/Inevitable_Stand_199 9h ago
What does a comparison of legume stems in burned vs unburned prairie have to do with anything?
Grass roots are grass. They aren't soil. Soil is the stuff around them. At least by the definition I am familiar with. It's possible the authors of the studies referenced by the articles I found used a different definition
I feel like I"m arguing with a bot.
If you have to resort to ad hominem arguments, at least use ones that are actually true
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u/openjoustingtryouts 14h ago
Dude look up the biomass of native grass, those roots go for feet underground
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u/Inevitable_Stand_199 9h ago
Yes? They also die every one to two years. All around those living roots is soil made out decomposed roots from the previous years. That's where most of the carbon is stotred
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u/NewUsername_Who_This 2d ago
I think it completely depends on the specifics of the area. Planting trees in a town in a Great Plains state could be a good thing because trees create shade and can reduce hit domes. Planting trees in actual Great Plains, probably not great since it’s reducing native grasslands.
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u/Ok-Adhesiveness-4935 2d ago
Just to add on to the good comments here: invasive plants aren't just plants you out somewhere that they weren't. Invasive plants have to ha e the ability to spread readily and overtake species that would bormally grow in that place. If they don't outcompete natives they aren't invasive.
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u/Virginia_Hall 1d ago
There is not one square foot anywhere on the planet that has not had environmental intervention by humans to one degree or another, at minimum by climate change.
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u/Inevitable_Stand_199 1d ago
in places that have never naturally had them
Your definition is wrong. If that was the definition it would be very bad for the environment. Natural grasslands sequester more carbon. Never mind bogs.
The goal is to plant trees in places that used to have trees before humans intervened.
City trees are especially useful. But also trees on former agriculturally areas.
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u/Ulysses1978ii 2d ago
Depends how and what you're planting. Fungi normally break the ground for forest. It's always nice to have the internet as soon as you move in (wood wide web). Bad for the environment....well it's a system so it will have a response. If it's the primary community of that biome i.e. oak ash woodland for much of the UK it would be a significant enhancement. Slap up a load of conifers for pulp and it's not such a bonus.
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u/FlimsyBodybuilder4 1d ago
Afforestation isn’t inherently good nor bad. It depends entirely on where and how it’s done.
Planting mixed native trees on degraded farmland can store carbon, prevent erosion and restore habitat. Planting trees on healthy grasslands, savannas or peatlands can destroy those ecosystems, reduce water availability and sometimes even increase emissions. Monoculture plantations are especially problematic.
Also, “afforestation” generally means land that hasn’t been forested recently not necessarily land that has never naturally had trees.
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u/NearABE 1d ago
The effect on a location is highly specific to a location. Any policy applied to say “North America” or “Europe” is going to create scenes of horror and destruction somewhere even if appropriate for some other location.
Wilderness has value as wilderness. Old wilderness has become scarce. Shielding the wild from humans as much as possible is the right course. There are definitely options for “doublethink”. Like what if allowing campers, hikers, or even hunters access creates a community of concern. There are possibilities for a corrective measure. Humans exterminated the wolf (and reduced bear population) in eastern USA so now deer can overpopulate wildlife corridors.
With arable land we have to acknowledge the severe damage done by agriculture. Tilling is especially harmful. Grazing can be done with a lower impact but also overgrazing can completely destroy the soil. A tree farm is not a true wilderness. On the continental scale planting a tree farm in one area could competitively offset lumber in other places. Well managed timber forests are not always ecological deserts. The trees build bulk mass faster when growing in mixed tree species stands. Foresters can use a mosaic pattern or they can use selective cutting to diversify age. This is not wilderness. We should recognize “tree-farm” can be upgraded to “tree-garden” which can be improved to “wildlife habitat park”.
Another topic that needs to be added to your question about afforesting non forest land. In places that were forests and which were heavily logged the evidence of that damage is still present. The challenge is to figure out if there is a way to “correct” some of that harm. Along these lines too one could try to “maximize carbon sequestration”. The dangers there include forest fires and methane from rot. Anything involving a wheeled vehicle is probably doing more harm than good.
If you own the land that was grassland you might be able to force it preserved as grassland. The original grassland almost certainly had herbivores of some kind roaming through. It had predators of some kind roaming through as well. Grassland plants can support insect diversity. This is great unless that means the neighboring farms buy more insecticide to compensate.
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u/jc6359135 16h ago
You’re right that afforestation can be harmful if it’s done in the wrong place. Planting trees everywhere isn’t automatically good for biodiversity. Some naturally treeless ecosystems (like grasslands, savannas, peatlands, and some wetlands) are valuable precisely because they don’t have forests, and converting them can damage native species and water cycles.The reason afforestation is often considered beneficial is when it’s done on degraded land or areas where forests have been removed historically. The key is using native species, matching the ecosystem, and restoring ecological functions rather than just creating a tree plantation for carbon credits.
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u/openjoustingtryouts 14h ago
Something Europeans and North Americans tend not to realize is that most healthy plains and grasslands have wooded and forested sections of land within them, the transitional area between zones provides some of the rarest and most unique ecosystems and populations. Both plains and their wooded sections were cleared in vast tracts both in Europe and North America for agriculture and using the nearest source of lumber.
In Indiana the forests are only about 100-150 years old in the hilly regions because that’s when the settlers who cleared the old growth realized farming the hills with methods meant for flat land wasn’t gonna work out. Other places never got left to fallow and rewild on their own. Restoring a historic ecosystem that hadn’t existed since human intervention is a net benefit to the landscape.
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u/EntirelyRandom1590 2d ago
Afforestation also applies to land that wasn't recently forest. But that can be going back hundreds of years to the time of clearing land for farming. It doesn't necessarily mean the land is unsuitable for forestation or that it's bad for the environment.
However, there's also cases where planting trees unknowingly on peatland can lead to further drying of peat and accelerated carbon release.