Imagine as a thought experiment
that you live in a small village and depend on
the local fish pond for food. You share the pond
with three other villagers. The pond starts off with a dozen fish,
and the fish reproduce. For every two fish, there will be
one baby added each night. So, in order to maximize
your supply of food, how many fish should you catch each day? Take a moment to think about it. Assume baby fish grow
to full size immediately and that the pond begins at full capacity, and ignore factors
like the sex of the fish you catch. The answer? One, and it’s not just you. The best way to maximize
every villager’s food supply is for each fisherman to take
just one fish each day. Here’s how the math works. If each villager takes one fish,
there will be eight fish left over night. Each pair of fish produces one baby, and the next day, the pond
will be fully restocked with twelve fish. If anyone takes more than one,
the number of reproductive pairs drops, and the population
won’t be able to bounce back. Eventually, the fish in the lake
will be gone, leaving all four villagers to starve. This fish pond is just one example
of a classic problem called the tragedy of the commons. The phenomenon was first described
in a pamphlet by economist
William Forster Lloyd in 1833 in a discussion of
the overgrazing of cattle on village common areas. More than 100 years later, ecologist
Garrett Hardin revived the concept to describe what happens
when many individuals all share a limited resource, like grazing land, fishing areas, living space, even clean air. Hardin argued that these situations
pit short-term self-interest against the common good, and they end badly for everyone, resulting in overgrazing, overfishing, overpopulation, pollution, and other social
and environmental problems. The key feature of
a tragedy of the commons is that it provides an opportunity for
an individual to benefit him or herself while spreading out any negative effects
across the larger population. To see what that means,
let’s revisit our fish pond. Each individual fisherman is motivated to take as many fish
as he can for himself. Meanwhile, any decline
in fish reproduction is shared by the entire village. Anxious to avoid
losing out to his neighbors, a fisherman will conclude that it’s in his
best interest to take an extra fish, or two, or three. Unfortunately, this is the same conclusion
reached by the other fisherman, and that’s the tragedy. Optimizing for the self in the short term
isn’t optimal for anyone in the long term. That’s a simplified example,
but the tragedy of the commons plays out in the more complex systems
of real life, too. The overuse of antibiotics has led to
short-term gains in livestock production and in treating common illnesses, but it’s also resulted in the evolution
of antibiotic-resistant bacteria, which threaten the entire population. A coal-fired power plant produces
cheap electricity for its customers and profits for its owners. These local benefits are helpful
in the short term, but pollution from mining and burning coal
is spread across the entire atmosphere and sticks around for thousands of years. There are other examples, too. Littering, water shortages, deforestation, traffic jams, even the purchase of bottled water. But human civilization has proven it’s
capable of doing something remarkable. We form social contracts, we make communal agreements, we elect governments, and we pass laws. All this to save our collective selves
from our own individual impulses. It isn’t easy, and we certainly
don’t get it right nearly all of the time. But humans at our best have shown
that we can solve these problems and we can continue to do so
if we remember Hardin’s lesson. When the tragedy of the commons applies, what’s good for all of us
is good for each of us.