[htamas]

The Amazon forest is unique in many ways but most importantly because unlike other forests, it CANNOT grow back. The reason for this is that it is a leftover from when the planet was covered in rainforests because it was a lot warmer and wetter in the Eocene epoch. The forest is sustained by the rain it creates from itself. Once the trees are gone, the water will be gone. [1] We also have reasons to think this self-sustaining climate is going to collapse soon [2]

So far the best way to protect it I have found is through the Rainforest Trust [3] which is a foundation that's trying to purchase and protect parts of the rainforests that companies would otherwise cut or burn down for agricultural use.

[1]https://youtu.be/hb3b-A6QAc8

[2]https://www.nasa.gov/earth-and-climate/human-activities-are-...

[3]https://www.rainforesttrust.org

[woah]

> The reason for this is that it is a leftover from when the planet was covered in rainforests because it was a lot warmer and wetter in the Eocene epoch.

Won't it get much warmer and wetter once global warming hits, allowing the rainforest to grow back?

[TSiege]

Not necessarily, (or even according to climate models I’ve seen). The feedback the OP mentioned is because trees near the coasts catch rain that they then respirate back up and create an atmospheric river that moves inland and falls as rain thus continuing the cycle inward. This cycle is disrupted by deforestation and can stop during a state change where it turns into Savannah. Savannah's are much drier and don’t cycle through water like the rain forest would. We’ll also see abrupt changes in global climate which will lead to completely different global rainfall patterns than we know today. For example the Sahara desert will likely turn into grassland/forest (which has happened in the past). The rainforest being a holdover from the Eocene is news to me, but my understanding was that the climate of the Holocene that we are leaving had weather patterns that facilitated a positive feedback with the Amazon rainforest expansion. From my understanding a thriving Amazon also necessarily depended on a desert Sahara as they drive weather/nutrient patterns that helps the Amazon

[ghm2199]

Without the trees, more rain may erode the soil, the Amazon river might flood more easily causing more erosion.

[blueflow]

Eocene temperatures: 6-15 kelvin above current. Would take another century or two of coal-burning to reach.

[TSiege]

We are already at Eocene levels of CO2 it’s just that our climate hasn’t caught up yet

[blueflow]

I think that's wrong, Eocene ended when levels had fallen to roughly 600-700 ppm? And we are at 480 ppm now.

[TSiege]

You are correct. I meant the Miocene where towards the end CO2 was ~500 ppm which we are over with CO2e.

[XorNot]

Global warming will not reforest the planet with a substantially different biosphere to set the conditions for the Amazon to regrow and then persist.

I mean I suppose it could but contingent on that would be things like "thousands of years" and "likely substantial extinction of human population centers".

[HappyPanacea]

How hard is it to plant it back?

[TSiege]

My understanding is very challenging for a few reasons. 1. A forest is not just a bunch of trees. It’s most healthy and robust with mature trees and right animal life that supports and propagates them 2. The short term economic incentives towards rehabilitating the forest aren’t there and are actively counter productive for soy and beef farming 3. It might already be past a tipping point as some parts of the forest are dying out and setting on fire through natural causes. The Amazon rainforest is NOT an ecosystem that is used to burning and it cannot recover from it since it destroys the ground cover and soils rainforest plants depend on to grow. Plants that like wet conditions need wet conditions to prosper, dusty charred clay ain’t that

[lokrian]

A lot harder than just not burning it down in the first place.

[saghm]

And even if it's somehow possible, it takes a lot longer too. Unless you're just moving the trees from somewhere else (which kinda defeats the whole point), you need to grow new ones, and trees take a pretty long time to get as large as the ones we're talking about.

[boccaff]

hard, and expensive, but doable as long as carbon credits are a thing: https://re.green/en/?force_locale=1

there are a few others in Brazil, like Biomas and Mombak