> trees will just naturally appear on unused land, there's no need to plant them. If this isn't happening on it's own, it's probably because the conditions there aren't right for them.
That is only true if the seeds can travel to get there! Moving many miles or uphill via seed dispersal is a slow process. The climate gradients and habitat pressures are moving much faster. While I agree that land suitable for forests will eventually reforest itself, if we want to do it on human timescales, we may need to kick-start the process with a seed transfer program.
That is only true if the seeds can travel to get there! Moving many miles or uphill via seed dispersal is a slow process. The climate gradients and habitat pressures are moving much faster. While I agree that land suitable for forests will eventually reforest itself, if we want to do it on human timescales, we may need to kick-start the process with a seed transfer program.