The quantity of the available resources is not nearly as much of a problem as the allocation. Subsistence farmers are not as productive on the same plot of land as industrialized commodity farmers.
We have more than enough land and water to feed everyone, but the (simplified) problem is that when one person does all the farming for the whole world, nobody else can afford to trade for any of it from them.
Surely the farmer needs clothing. So he will trade with the sole cloth maker. Surely the club maker needs threads and dyes, so she will trade with the due maker and the thread spinner... And ad infinitum.