Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape

Globally, colonialism resulted in the suppression of aboriginal land management practices, abetted by the concept of terra nullius, belonging to no one; the belief that aboriginal people had little influence on or ownership of the land. Until recently, this ideology was entrenched in resource management and policy. Traditional ecological knowledge, historical ecology, archaeology, and palaeoecological research have shown these assumptions to be wrong. In this paper we take a multidisciplinary approach (biogeography, paleoecology, dendrochronology, and bioclimatic envelope modeling) to better understand the role of climate and fire in the formation of eco-cultural landscapes. We synthesize results from pollen and charcoal analysis in Garry oak ecosystems that indicate there were continuous and frequent prescribed burning events, with more severe fires occurring every 26-41 years in southwest British Columbia throughout the Anthropocene (similar to last 250 years) that substantially altered forest structure and composition. These results are consistent with stand age reconstructions in BC and Washington with Garry oak establishment beginning similar to 1850 AD, corresponding with modern fire exclusion, aboriginal population decline, and end of the Little Ice Age. Douglas-fir recruitment has been continuous since similar to 1900, with succession of oak woodland to closed conifer forest at most sites. These findings indicate that the structure of many Garry oak ecosystems have been profoundly influenced by eco-cultural practices. Overwhelming evidence indicates that in many cases these ecosystems are dependent on prescribed fire for their open structure. In the absence of aboriginal land-management practices, active management will be necessary to maintain Garry oak woodland.