SciencePrehistoricAmericashigh confidence

A study estimated that the extinction of Ice Age megafauna removed just under 10 teragrams (about 10 million tons) of methane emissions, accounting for at least 12–15% (and possibly up to 100%) of the methane reduction at the start of the Younger Dryas.

Notes on verification

Confirmed by the peer-reviewed 2010 Nature Geoscience study (Smith et al.) and corroborated independently by Smithsonian Institution and University of New Mexico press materials. Minor rounding discrepancy (12% vs 12.5%) is negligible. [tier=gold indep_score=0.92 clusters=5 claim_tier=notable]

Sources