The only problem is that we don't have nearly enough space for that.

An acre of trees stores ~393 tonnes of carbon dioxide permanently (in Vermont anyway, other areas probably vary a lot) [1]

Humans generate ~40 Gtonnes of CO2 a year. That means we need to be adding ~100 million acres of trees every year to capture that. There's currently 4 billion hectares of forest cover - that's around 10 billion acres.

If we replanted every area which has seen deforestation since 1990 we'd get another 400 million acres, or 4 years of emissions. After that, we're fighting an uphill battle. Forests currently cover 31% of the earth. 29% of that surface is desert, 3% is urban areas and 10% is covered in ice. To keep on top of emissions we'd need to add 0.3% of the total each year globally, or 1.2% of the land which could actually grow trees.

That might be doable in 5 years, but 10 years? 15 years? 30 years?

Re-forestation may be part of the solution, but it can't be the only part.

[1] (PDF}: http://fpr.vermont.gov/sites/fpr/files/Forest_and_Forestry/T...

[2]: http://www.earth-policy.org/?/indicators/C56/

There is a lot more area in the ocean and seaweed grows very quickly. Perhaps we could even accelerate the sequestration by building large seaweed farms over the deep ocean, then sinking the seaweed once it grows large enough, & repeat.

Related: https://oceana.org/blog/seaweed-could-be-scrubbing-way-more-...

I think this is going to have to happen for bio capture to work at all. We need land for food, and we'll need increasingly more of it in the next decade thanks to overfishing, and population growth

Or use it to build homes, which still keeps it out of the atmosphere