Have we reached peak food? It's certainly becoming a popular claim again, just like it did in the 1960s and all the way back to Thomas Malthus and even earlier. Every time there was a famine, humanity had exceeded technology and we were in peril. Yet science has always bounced back. After the food scares of the 1960s, science began creating ways to produce more food than ever.
Yet we know food scarcity can't be approached passively. The close of the Permian Period around 250 million years ago saw Earth's biggest extinction ever, after large volcanic eruptions in Siberia pumped out gases that led to acid rain and the decline of food. And the food industry today can help us understand the past.
Falling on the supercontinent Pangaea, the acid rain killed off end-Permian forests. The demise of forests led to soil erosion and the production of organic-rich sediments in shallow marine waters. The sediments are now rocks in cliff faces in the Italian Dolomites, and studying them provides insight into the mechanisms of Permian ecosystem decline. Scientists have proposed a first-ever, organic compound-based, quantitative recorder of acidity for the geological record.
Knowledge from the food industry, where vanillin ("vanilla") is used as a flavoring ingredient, shows that oxidation of vanillin to vanillic acid is reduced under acidic conditions.
Ratios of vanillic acid to vanillin in end-Permian organic matter reveal soil acidity close to that of vinegar or lemon juice. Acidification events occurred not once but several times as volcanism hit the land with repeated pulses of acid rain. An acid-induced decline in plant life would have caused a collapse in the food chain, sealing the fate of end-Permian life on land.
Citation: Mark A. Sephton et al., Terrestrial acidification during the end-Permian biosphere crisis?', Geology doi.org/G36227.1