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For one thing, the impact of human pollutants on nature can be vastly amplified by food chains, the serial process by which weak creatures are typically eaten by stronger ones in ascending order. The most closely studied example is the effect of pesticides, which have sharply improved farm crops but also caused spectacular kills of fish and wildlife. In the Canadian province of New Brunswick, for example, the application of only one-half pound of DDT per acre of forest to control the spruce budworm has twice wiped out almost an entire year's production of young salmon in the Miramichi River. In this process, rain washes the DDT off the ground and into the plankton of lakes and streams. Fish eat the DDT-tainted plankton; the pesticide becomes concentrated in their bodies, and the original dose ultimately reaches multifold strength in fish-eating birds, which then often die or stop reproducing. DDT is almost certainly to blame for the alarming decrease in New England's once flourishing peregrine falcons, northern red-shouldered hawks and black-crowned night herons.
In the polluting sense, man is the dirtiest animal, and he must learn that he can no longer afford to vent smoke casually into the sky and sewage into rivers as he did in an earlier day, when vast reserves of pure air and water easily diluted the pollutants. The earth is basically a closed system with a waste-disposal process that clearly has limits. The winds that ventilate earth are only six miles high; toxic garbage can kill the tiny organisms that normally clean rivers. Today, industrial America is straining the limits.
One massively important factor is that the U.S. consumer actually consumes nothing; he merely uses things, and though he burns, buries, grinds or flushes his wastes, the material survives in some form, and technology adds to its longevity. The tin can used to rust away; now comes the immortal aluminum can, which may outlast the Pyramids. Each year, the U.S. produces 48 billion cans, plus 28 billion long-lived bottles and jars. Paced by hardy plastic containers, the average American's annual output of 1,600 lbs. of solid waste is rising by more than 4% a year. Disposal already costs $3 billion a year.
All this effluence is infinitely multiplied in big cities—and 70% of Americans live on only 10% of the country's total land area. Every day, New York City dumps 200 million gallons of raw sewage into the Hudson River. Each square mile of Manhattan produces 375,000 lbs. of waste a day; the capital cost of incinerating that 1-sq.-mi.-output is $1.87 million, and 30% of the residue drifts in the air as fly ash until it settles on the citizens.