Food production uses fertilizers (from fossil fuels) and pesticides (from fossil fuels) and machinery (running on fossil fuels) to grow foods which are then processed (by machines running on fossil fuels) and shipped around the world (using fossil fuels).
We are talking about long-run trends of food insecurity. Russia's invasion of Ukraine will probably be (and hopefully) a short temporary turn in the wrong direction
Fertilizer production uses a great deal of natural gas.
The claims of fragility are unfounded though as natural gas supply isn't going anywhere and the use of natural gas in the process could be trivially (at great expense) replaced entirely by [nuclear powered] water electrolysis.
We also grossly overproduce calories, both as a policy decision for anti-fragility and for raising meat. Both of which leave a lot of slack before starvation levels kick in. At least in the US, other countries may be closer to the limit.