Human‐mediated trophic mismatch between fire, plants and herbivores

Trophic mismatches are commonly reported across a wide array of taxa and can have important implications for species participating in the interaction. However, to date, examples of trophic mismatch have centrally focused on those induced by shifts in climate. Here we report on the potential for humans to induce trophic mismatch by shifting the phenology of fire. Globally, anthropogenic fire ignitions are phenologically mismatched to that of historic lightning ignitions but the effects of this phenological mismatch on trophic interactions are poorly understood. Using fire records from 1980 to 2016 from the southeastern USA, a hotspot of anthropogenic fire, we demonstrate that there is a temporal mismatch between anthropogenic and lightning lit fires in this region. The peak of anthropogenic ignitions (i.e. 45% during March and April) occurred 3 months earlier than the peak in lightning-ignited fires (i.e. 44% occurred during June and July), a pattern consistent with reports from several other regions and continents. We demonstrate with a field experiment conducted at a nutrient-poor site in the southeastern U.S., that anthropogenic fire phenology shifts nutrient pulses in resprouting plants so that they mismatch herbivore reproductive demands. Consequently, plant nutrient quality in four commonly consumed forages was below the threshold to meet lactation requirements. Neonates subsequently were more likely to starve when born far from areas burned during the peak month of lightning fire phenology. Our data indicate that human activities may be an additional causative agent of trophic mismatch.