The success of the drive to introduce new high-yield varieties tends to exacerbate the instability of the international crop trade in agricultural commodities; import demand from previously low-producing countries leading to price falls and surpluses in exporting countries. The resulting shifts in trade patterns make price stabilization more difficult. Although regulating the growth of plants is as old as farming itself, the use of chemical compounds in agriculture has been one critical aspect of the contemporary explosion of crop yields. It remains to be fully seen what environmental effects these unnatural manipulations of the food chain will have in the long run.