Workers from Stanford Facilities are currently spraying trees around campus with high-pressure water hoses. They are trying to head off Stanford’s annual plague of caterpillars by knocking moth larvae out of the trees.

But a more elegant solution to the caterpillar problem may be to instead rein in light pollution on campus. Much of the campus’s lighting radiates towards the sky, which both obscures our view of the night stars and attracts insects (like moths) from miles around. Solving Stanford’s lighting problem would both reduce energy use and conceivably help solve our caterpillar problem. The matter warrants further investigation by the University.

Picture for a moment the lampposts in the middle of campus. They are black poles topped by glass domes that house the light bulb. Under this design, about half of the light emanating from each lamppost shines above the horizontal plane, upwards into the sky. These misdirected lights are not just wasteful but also polluting.

The University ought to commission an external evaluation of its outdoor lighting system. Unnecessary use of stadium lights must continue to be restricted. New lampposts should have “fully shielded” lamps that block vertical light. And Stanford should retrofit existing lightposts with covers, redirecting stray light back towards the ground where it belongs.

Tussock moths, the genus of caterpillars and moths that swarm our campus each year, have a long history of infesting urban areas. An entry in American Naturalist from 1893 describes “myriads” of tussock moth caterpillars descending upon Chicago. The author wrote that the moths are “attracted by artificial lights” and congregate around lit shop-windows. Today’s entomological literature confirms that tussock moths are attracted to lights and that moths will migrate from miles away towards well-lit areas. These findings may explain why well-lit Stanford teems with caterpillars each year while dimly-lit nearby Atherton, according to interviews with local residents, does not.

Granted, the link between stray light and Stanford’s caterpillars is difficult to prove. The damage caused by light pollution, however, is beyond doubt. Studies demonstrate that light pollution wreaks havoc on the ecosystem by disorienting migrating birds, distorting rodents’ Circadian rhythms and drawing insects (for instance, the tussock moth) from miles away out of their natural habitats. Students taking Prof. Dement’s “Sleep and Dreams” learn that light also disturbs humans’ sleeping habits.

The stray light additionally obscures our view of the stars. In relatively unlit areas, one can still see the Milky Way, the tremendous white band of our galaxy’s stars that streaks across the night sky. Yet from the Stanford campus, one can hardly even make out the constellations. The Lick Observatory outside San Jose has been so affected by local light pollution that San Jose has retrofitted most of its streetlamps. The lamps are fully shielded and have low pressure sodium bulbs that the observatory can easily filter. Stanford can follow the local community’s lead by introducing light-dimming measures of its own. In doing so, the University would probably save money — Calgary’s streetlamp retrofit saves the city millions of dollars each year in energy costs; as less light is wasted, less power is needed to provide the same amount of illumination.

On a happy note, not all of Stanford’s lamps pollute. The lamps found outside Encina Commons, for example, are covered on top with a reflecting surface. If a retrofit proves unfeasible, hopefully the University will employ this “fully shielded” design on at least all new streetlamps.

At a time when the University inaugurates a new building for the study of the environment and sustainability, when it tells students to conserve by replacing their incandescent light bulbs with compact-fluorescent lamps and when it replaces students’ high-flow showerheads with low-flow showerheads, it ought to get its own conservation house in order. Stanford’s light pollution damages the environment and wastes energy, yet it can be stopped quickly and cheaply. That way, Stanford might remove the caterpillars from the ground and reestablish the stars in the sky.