Restoration More Complex than Rocket Science

August, 2014






Restoration is not rocket science; it’s harder than rocket science.  Rocket science is complicated, but the physics involved are well known, and the objectives are clear.  Restoration involves sciences such as ecology that are less developed than physics, and arguably more difficult; ecosystems are complex and non-linear, with some  strongly and many weakly interacting parts, and are subject to constant change and to stochastic influences from outside the system.   Predicting how ecosystems will respond is notoriously difficult.

Beyond that, the objectives of restoration are not always clear. The implied objective of restoration is to restore some previous condition, but that begs the question, which previous condition?  We could say natural conditions, but we don’t know the natural condition of the Mattole basin, and even lack a clear idea of what we mean by “natural.”  Humans are relative newcomers to the area, but were here modifying the landscape (especially by burning) before the climate and sea level stabilized at the end of the last ice age.  Were these humans part of the natural condition?  If not, natural conditions have not existed since the ice age, and if so, when did conditions become unnatural?

To anchor this discussion, consider the Mattole River lagoon.  We have a good map of the lagoon in 1871, from careful work by the U.S. Coast Survey.  It is tempting to think that this shows the natural condition of the lagoon, but 1871 was only a decade after the flood of record for the state, in the winter of 1861-62.  Information on the effects of the flood on North Coast rivers is scant, but the observations of wood on the beaches near Crescent City by William Brewer, a scientist with the first geological survey of California, give a strong hint:

“The floods of two years ago brought down an immense amount of driftwood from all the rivers along the coast, and it was cast up along this part of the coast in quantities that stagger belief.  It looked to me as if I saw enough in ten miles along the shore to make a million cords of wood.  It is thrown up in great piles, often half a mile long, and the size of some of these trees is tremendous.  I had the curiosity to measure over twenty.  These were worn by the water and their bark gone, but it is not uncommon to see logs 150 feet long and 4 feet in diameter at the little end where the top is broken off.  One I measured was 210 feet long and 3½ feet at the little end, without the bark.”

What happened that winter in the Mattole basin is unknown, but with weeks of rain, conditions must have been ripe for debris flows that carry trees, soil and rock into the river, wreaking major channel change and increasing the flow of sediment and large wood to the lagoon.  

“The 1861-62 storm period was by far the wettest ever recorded in northwestern California. Over 1,270 mm of rain fell at Fort Gaston between November 24 and December 8, 1861, and the January 8-11 storm produced an additional 305 mm of precipitation.  Rainfall records were not available for the 1867, 1879, 1881, and 1888 floods. The Eureka Humboldt Times reported that over 787 mm [31 inches] of rain fell at the Upper Mattole station during the storm of January 27-31, 1888” (Harden, 1995, USGS Prof Paper 1454-D).

Lagoons, like rivers, are subject to major change during floods, so the lagoon in 1871 most likely was different than before 1862, or after 1888.   

What about restoring the forests, so badly abused by tractor logging in the 1950s and 60s?  Here again, the natural condition is unclear; humans have been setting fires since the late stages of the last ice age, and fires affect the composition and distributions of forests and grasslands.  There is good evidence that much of the fir forest cut in the logging boom, especially on the south facing slopes, was established after the Anglo settlement, when burning by Native Americans diminished.  Currently, the scarcity of fire is allowing the fir forest to expand into former woodlands and meadows.  

Because we don’t know what natural conditions were, the objectives of restoration are largely up to us.  Most of us want the lagoon to be good habitat for young salmon on their way to the ocean, and are trying to make it so, but some may think we are giving too little attention to birds.  We are less clear about the forest; some of us think that extensive fir forest indicates recovery, and some of us think that the forest is taking over what should be grasslands or oak woodlands, and reducing the dry season flow in streams.  Practical and aesthetic factors also influence our thinking.  Ranchers naturally favor grass, and loggers favor forests.  Trees may block views, provide habitat, shade and windbreaks, and increase the hazard from fire.  

The upshot for restoration is that our objectives as well as our methods deserve careful consideration and questioning, and learning should always be one of the objectives.  Restoration is always experimental, whether we want it to be or not, and we should try to make our restoration projects as informative as we can.  

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