And to what extent climate change would make the environment no longer suited for trees?
In the US forest fires burn about 7 million acres on average each year.
https://sgp.fas.org/crs/misc/IF10244.pdf
https://en.wikipedia.org/wiki/List_of_California_wildfires
The Dixie fire alone was about 1 million acres.
San Francisco is 30,000 acres for perspective.