Sunday, February 11, 2018

Point of Failure

Nurse Log. Hoh Rain Forest, Olympic National Park, WA. Photo Taken 9/4/15.

Trees growing out of trees. That old, dead tree lying on the ground that supports the newer trees is called a Nurse Log, as in, it nurses the young trees until they can stand on their own. Many old trees started out as young trees growing out of old trees.

The wheel, the pulley, the inclined plane, screw, wedge, lever, these were early machines. In the beginning, they were simple, made of wood, stone, or raw metals. Today, machines are usually elaborate complexes or systems of these simple machines. An example would be a jet engine.

In a system or machine, there are points at which failure can occur. Some points are more prone to failure than others and some points are more critical than others. Some points of failure will stop the entire machine. These are called Single Points of Failure. This is an undesirable state; such a machine is highly vulnerable to total system failure. Imagine a jet engine flywheel breaking apart and slicing through the hydraulic lines while cruising at 40,000 feet.

The ideal is to create redundancies, that is, to duplicate critical functions within the machine. That way, if one function fails, a duplicate function takes over and the machine can continue to operate. That is one reason a passenger jet has multiple engines. This is important while travelling eight miles high.

It is also important on the ground. To understand this, we must consider the experience of the mythical Jedediah Clampett. According to the legend, when he discovered crude oil on his property in Limestone Tennessee, it came to the surface under its own power. A small hole punched in the ground by an errant bullet provided relief to the pressurized oil trapped underground. Why, it flowed out of the hole like water from a garden hose and the bubbling crude made old Jed a millionaire.

At that point in time, his machine for oil extraction was no more than a shovel. A shovel is a simple machine, just a wooden handle, a pin, and a blade. It acts as a wedge and lever. Each is a Single Point of Failure. One of those breaks and the tool is useless and Jed is unable to gather any oil. He tosses the handle into the woods, drops to his knees, scoops the oil with a flat rock, and gently eases back into the Stone Age.

Today, it is unusual to find an oil field that pours from the ground under artesian pressures. Most of the new oil is found at the margins of extractability: in shale, sand, offshore, deepwater. A shovel will not do. It requires an exceedingly complex machine, a myriad of pipes, valves, gauges, wires, alarms, switches, and sensors. The possible points of failure become innumerable. The Single Points of Failure also increase, requiring a complex arrangement of redundant functions. However, this increases the risk of total system failure and a calamity. In the Deepwater Horizon disaster, there were numerous points at which failure occurred - a blowout preventer, two mechanical valves, one battery, one gas alarm, a defective switch, and human oversight - all of which conspired to create a total system failure. Eleven lives were lost, 4.9 million barrels of crude poured into the Gulf of Mexico, and 52,590 tons of mangled metal settled to the bottom of the Gulf. This was just one machine. The planet is littered with millions of broken machines; in landfills, backyards, war zones, junkyards, garages, parking lots, sealed in concrete bunkers, ravines, at the bottom of the sea, tumbling in earth orbit. What to do?

A tree is a machine. A large tree functions as a water pump, oxygen generator, carbon sink, weather moderator, fog filter, windbreak, birdhouse, soil stabilizer, food source, to name a few. As with other machines, at some point, it experiences a total system failure, whether it's from drought, insects, lightning, windthrow, climate shift, fungus, landslide, overshading, hydrologic changes. Add them up and there are millions of failure points in a tree. Yet these provide opportunities for other living things. Spring ephemerals take advantage of fall leaf failure and prosper in the abundant spring sunlight. Microorganisms on forest floor take advantage of needle failure and turn them into nutrients. Campers take advantage of branch failure and roast marshmallows. Insects and birds take advantage when the whole tree fails and build apartments. Other trees take advantage of a fallen tree and drop their seeds into the rotting carcass where they germinate and thrive. Trees grow out of failed trees. This machine is designed to fail.

Fail as they may, we have searched the newspapers and it is very difficult to find accounts of massive explosions, tragic loss of life and limb, toxic chemical spill, or power grid failure associated with the death of a tree, despite millions of them occurring every year since the late Carboniferous period.

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