Classical X-shaped supply and demand curves are fine as far as they go - ie they're a reasonable shape over a
small relevant range of volumes of production and sales. However, the supply curve and the demand curve are both non-linear in many instances outside a very narrow range of volumes and prices. Taking that into account, and using a hypothetical example where all externalities were built into the costings, the supply and demand curves might look something like the graph above. The supply curve is S-shaped because at high volumes, measures such as pigovian taxes make it exhorbitantly expensive to produce and sell each further unit. This could
result in annual aggregate volumes of production and sales of product of V1 and P1 respectively at equilibrium - and V1 being well below the levels at which bio-capacity would be damaged irreparably.
Population growth (and increasing consumption per capita) would push the whole demand curve up and
right. This would never push the equilibrium point (where the curves cross) beyond a volume of V3, so sustainability would be maintained. However, the price at equilibrium point would rise. Where population and consumption trends approached planetary limits, the price at equilibrium would rise dramatically.
This is why, in my view, sustainability and social equity/poverty are so inextricably linked as policy areas for global governance - a sustainable world might be a very expensive world and require much more significant welfare
systems or income/wealth redistribution systems to avoid the effects being felt disproportionately by the poorest sectors of society.