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Human Time, Ecological Time and Fire Return Time

posted Jul 24, 2015, 1:54 PM by Joe Christy

Last month I had the pleasure of hearing a wonderful presentation by Grey Hayes about the ecological significance of our Santa Cruz County North Coast. One remark in particular stuck with me: that we humans look out at at undeveloped lands and see an unchanging ecosystem, when in fact the ecology is dynamic, over time periods longer than we are accustomed to thinking about.

Our mountain was clear cut between the 1890’s and 1910’s. There are very few old-growth redwoods left on our mountain and most Dooners have never seen them, due to their remoteness. Nowadays, sustainable forestry in redwoods aims for a harvest cycle of around a century while maintaining the redwood community so, for example, one might aim to cut 10% of the trees, chosen individually, in a commercially managed forest in rotating harvests every 10 years. Obviously, the turn of the twentieth century harvest was long before the concept of sustainable forestry. Near the end of the clear-cutting era here, American foresters, responding to catastrophic wildfires in the northern Rockies, seized on the goal of absolute fire suppression. Professionals only began to understand the folly in fire exclusion late in the last century, and the public at large has yet to come to grips with the idea that fire is an essential part of nature.

For eight to twelve thousand years before the advent of the Spanish mission in Santa Cruz around 1800, the Ohlone people regularly burned their surroundings, from the coast to maintain the prairies which supplied the grass seeds they ate, to the oak savannahs which furnished acorns, into the coniferous forests where they hunted in the autumn. Studies reveal that in the redwoods they would burn the areas between their forest trails about every decade. Between the Ohlones’ forced move into the missions and the onset of logging, fires in the redwoods were largely due to lightning, which modeling predicts would return on an average interval of around a century.

In the southern province of the redwood range, from the Golden Gate to Big Sur, old growth redwoods are generally between 600 and 800 years old. Redwoods were here when the Ohlones’ ancestors arrived, in a radically different climate, after the end of the last ice age. There have been about as many generations of redwoods here during the period of traditional management, with its frequent low intensity fires, as there have been human generations since Europeans arrived and shifted the fire return interval in redwoods far beyond the average human life span. To the extent that there is a relevant natural state for our local environment, it is that of indigenous stewardship.