For much of human history the transport of agricultural goods over long
distances has been impractical because the means of transport have been slow
and many foodstuffs are perishable, and because the cost of moving commodities
in bulk has been prohibitively high. This had many consequences for
farming and the economy in general. It limited the growth of cities because
the area needed to feed urban non-agricultural populations was large with the
low productivity of agriculture before the nineteenth century; the cost of
movement soon equalled the price of the crop transported. It made regional
specialization in one or two products for which an area had physical advantages
difficult, for each area had to produce as much of its food supply and
fibres as possible. It meant that comparatively little agricultural produce
entered into trade unless the product had a high value per unit weight (such as
wool) or could be moved in the relatively cheap coastal shipping trade. Early
regional specialization was thus associated with low-cost movement.