The Short Version
While fire can reduce plant productivity — the ecosystem's energy base — the leap to "fewer trophic levels" is not supported by the strongest available evidence. Peer-reviewed studies show that post-fire ecosystems often shift energy pathways (e.g., from detritus to algae-based food webs) or rebound through early-successional regrowth, maintaining multi-trophic structure even when individual species abundances decline. The claim conflates reduced biomass with the elimination of entire trophic levels, overstating fire's structural impact on food webs.