It’s not that we fear the future populations will not have enough food to feed themselves, it’s a mere fact that food would be less affordable, for many people. Food is often grown in plenty, you will find in a single nation there are thousands of farmers who are unable to sell their produce, because it would cost them great losses, if they were to sell at such a low price they’d be put out of business. Some crops grow stale in the fields while they wait for harvesting, others are bore into by aphids in the grain stores as they wait for shipping creating a huge wastage.
Mechanization has increased food production in the last century, but it has also made it expensive just like in the field of medicine. Something which was considered inefficient and relatively cheap in the early days can now cost you an arm and a leg, like the common case of just a simple medical check-up.
A group of environmentalists drum into people’s heads that they need to grow more food for the bulging populations, so when farmers clear more land for cultivation, they say stop, you are destroying valuable forests, farmers are then forced to leave such a premise and head towards barren soils, they add fertilizers to the grounds to make it more productive. The same scientists stubbornly rush in asking them to stop, claiming they are leeching the soils, what do you want us to do then? Tell us more of your poor reasoning.