I googled some and it looks like Amazon rainforest alone removes about a quarter of fossil fuel CO2 from the atmosphere. That's more than I thought it'd be. And it looks like it could sequester much more if there was more phosphorus in the soil.
Quote: "The Amazon Basin is critical to help mitigate climate change due to its trees absorbing around a quarter of the CO2 released each year from the burning of fossil fuels."
The specific quote is talking about trees in the rainforest, not the rainforest itself. The rainforest is an ecological system that also produces CO2 (mainly through microbes breaking down wood) and you can't ignore the rest of the system.
Which is not to say that the Amazon doesn't play a significant in the global environment and weather systems.