It is a fact unless you can demonstrate that the rate of petroleum production will increase in the future.

The law of supply and demand is not a theory.

You misunderstand; All these inputs aren't solely dependant on petroleum. Pesticides and fertilizer can easily be manufactured with nuclear process heat and electricity, and diesel fuel can also at a high price.

Second, fuel demands for agriculture are relatively low while food demands are relatively high. There are plenty of surplus industries that will die first, from airlines to large commuter cars.