A MEGA-FIRE HYPOTHESIS FOR LATEST PLEISTOCENE PALEO-ENVIRONMENTAL CHANGE ON THE NORTHERN CHANNEL ISLANDS, CALIFORNIA

Recent research on the Northern Channel Islands of California has seen a growing convergence in the ages of several key events, suggesting that some or all of them may have occurred at or around 13,000 cal yBP. These events include (1) paleo-botanical transformation, apparently very rapid, of the islands from pine cover to non-arboreal vegetation; (2) onset of voluminous lowland aggradation; and (3) deposition of charcoal and disseminated carbon. Other events with ages converging on ~13 kyBP include: (4) the arrival of the first humans on the NCI, and (5) extinction of the Pleistocene mammoth population.

A number of mechanisms represent credible causes of the latest Pleistocene events and changes on the NCI, including climatic warming and desiccation, ecosystem reduction due to post-glacial sea-level rise, and vegetation changes driven by increased fire frequency (perhaps driven by decreased precipitation). All of the preceding mechanisms represent gradual explanations for gradual changes. An alternative mechanism is suggested here – abrupt and simultaneous occurrence of all of these changes as a result of a single extreme, island-wide, high-temperature fire (or “mega-fire”). Given recent archeological data showing humans present on the NCI by or shortly after 13 kyBP, it is at least credible that such a mega-fire was triggered by the first migrants along the western margin of North America.

The mega-fire hypothesis – if verified – could have broad implications for early humans in the Americas and their interactions with, and impacts upon, the environment. One potential paleo-environmental analogy may be Easter Island, and the apparent rapidity at which that environment was degraded. Other related issues include the first migration routes into the Americas, causes of late Pleistocene mega-fauna extinctions, and recent speculation about early human impacts upon global climate.