Net land area suitable for arable production may well remain roughly constant, but only over timescales much longer than a human lifespan due to the speed at wh

Net land area suitable for arable production may well remain roughly constant, but only over timescales much longer than a human lifespan due to the speed at which ecological succession operates. For instance, when permafrost melts the land left behind is extremely uneven, covered in marshy hollows and collapsing pingos. Where soil exists, it is thin and biologically inert. Primary succession to the point where it is suitable for intensive arable production will take at least a millennium, even if there are no further changes to the climate. Now, it's likely - human ingenuity being what it is - that we'd be able to use that new land for some form of agriculture well before that, perhaps even within a century or two. But if we do, it'll be through something like genetically-engineered moss and sedges, not intensively growing wheat and corn in northern Siberia!