[kokanee]

Some would argue that where conditions for trees aren't suitable, the solution is to build a forest there. Forests themselves are the best terraforming tool, if you can get them started by supplying the necessary nutrients, energy, and water.

I don't know how feasible it is, but using trees to transform parched landscapes is the mission of a company I interviewed at a while back called Terraformation, founded by the former CEO of Reddit.

[sitkack]

To add reference to the claim that, "forests themselves are the best terraforming tool", one can take the example of Ascension Island. With the introduction of outside trees that formed an ecological foothold, they started cooling humid air and reinforcing the soil so that other plants and trees can flourish.

https://en.wikipedia.org/wiki/Ascension_Island#Botany

https://www.bbc.com/news/science-environment-11137903

Once, This Island Had Just One Tree https://www.youtube.com/watch?v=TZPrk9IZ3Jw

[robocat]

Looking at the satellite photos, a lot of the Island is still quite barren.

Strangely enough, the Google maps satellite imagery is almost useless. Use Apple maps instead. If not on an Apple device, you can access Apple maps via https://duckduckgo.com/?q=ascension+island (note: satellite imagery is not available this way on my iDevice).

Here is another BBC article, which I think is far more balanced and talks about the negative issues of the biological cost of the planting: https://www.bbc.com/news/magazine-36076411

The last volcanic eruption was 1508 or so. I did a quick Google to find some information on how long takes it generally takes for vegetative regeneration after volcanic eruptions. Looks like it depends on type of eruption and rainfall: “Mount Kelud in East Java has erupted on a 15–37-years cycle for the past centuries [snip] Within 3 years of the eruption, stem diameters were 3–10 cm. [snip] being able to establish itself rapidly in the extreme conditions that prevail after a recent ash deposition event (given the short return period of eruptions), but by enriching the ash deposits with nitrogen, paves the way for grasses to take over, which in turn delay succession to other woody vegetation” (not sure if the landscape was purely volcanically virgin). Obviously it can also takes centuries in the example of Ascension. A study in Hawaii looked at the order that types of vegetation took hold: https://www.nps.gov/parkhistory/online_books/science/5/chap8...

[jandrese]

The caveat with this is the forests can do ok for awhile, but then a dry spell will hit and it tends to burn down.