Human land use is incredibly inefficient. As a simple example, in the US the vast majority of corn production is ethanol or animal feed (which is incredibly inneficient on a calorie basis). Then when you take into account low density residential and their endless lawns (turf grass has by far the most acres of any crop in the US) and a million other poor uses of land and there's a lot we can do, even at 8 billion people, without destroying every forest.

The issue isn't that the problem isn't solvable, there are tons of things that have huge environmental benefits. The problem is that these generally require some sacrifice (e.g. denser housing with much smaller lawns, eating more resource efficient foods like lentils, moving away from fossil fuels) but there's not sufficient collective will for actually doing these things.

I think such problem are unsolvable. In America, people can't live without meat and they will always justify it by bringing pasture raised cattle farm :/