While it is true that Ukraine and Russian harvests will be lower than usual, that is not the only problem. Due to less availability of natural gas fertilizer production is down and fertilizer is much more expensive. This has especially affected crop yields in South America. Due to very heavy rains China announced its winter wheat yield will be down by more than 20%. Shortages, energy curtailments, inflation will not only diminish supplies but the increased prices will make food inaccessible for poor people around the war. If there is a natural or weather disaster in India or China, real famine would be likely. Social, political and economic disorder will follow. There will be more wars.
Not long ago cheap natural gas was driving ag production and farm income via fertilizer cost reductions. Biden has ruined all this.