If you expand forests it's a one-time sequestration. That's my point.
> One doesn’t count rainforests or boreal forests as “zero carbon” capture. They have an ongoing capturing capacity.
Each ecosystem has a turnover time. For rainforests it's like 20 years. For tundra it's as long as 65+ years. But in a stable state these carbon "sinks" are net zero carbon capture. For every ton of carbon they capture, a ton of carbon is released through decomposition.
A recent study published in 2019 said that if total emissions, agricultural land use, and other factors remained steady, planting trees might buy us 20 years: https://climate.nasa.gov/news/2927/examining-the-viability-o...
The problem is that we're pumping out alot of carbon: about 10GtC/year. The entire Amazon rainforest sequesters only about 100-200GtC. Actually, the biggest problem as I said is that we're pumping out carbon from a resource (Carboniferous period deposits[1]) that can never again be recreated, at least not without significant geoengineering.
[1] Carboniferous deposits occurred at a golden period, immediately after woody trees first emerged, but before microorganisms evolved that could decompose them; trees could be buried long enough to fossilize before microorganisms could release all the carbon back into the atmosphere. That can't happen today naturally, at least not at any scale that could help us.