82 Scientific American, April 2022
Naomi Oreskes is a professor of the history of science
at Harvard University. She is author of Why Trust Science?
(Princeton University Press, 2019) and co-author
of Discerning Experts (University of Chicago, 2019).OBSERVATORY
KEEPING AN EYE ON SCIENCE
Illustration by Yifan WuRachel Carson’s classic best seller about ecological threats, Silent
Spring, started a wave of American environmentalism. It played
a direct role in the 1972 decision by the newly formed U.S. Envi-
ronmental Protection Agency to ban use of the pesticide DDT.
Ernest Gruening, one of the first two U.S. senators from Alaska,
said Carson’s writings had “altered the course of history.” It will
be 60 years ago this June that the public was introduced to Car-
son’s arguments, as her book chapters were serialized in the New
Yorker magazine. The coming anniversary makes this a good time
to consider whether the book achieved one of her major goals:
protecting wildlife and, in particular, birds.
Carson took a complex technical subject—the damaging effects
of persistent pesticides—and expressed it in one simple, poetic
image: a spring in which no birds sang. She asked us to imagine
what it would be like to awaken in the morning to a world with-
out these songs. She wrote with grace, and she made us feel the
loss. But how well have we acted on Carson’s warnings?
With some exceptions, we haven’t been very successful, and
neither have birds. In 2019 a major study, led by Cornell Univer-
sity ornithologist Kenneth V. Rosenberg, showed that 29 percent
of North American birds have vanished since 1970. The study was
notable because of its sweep: it integrated data across scores of
species and the different biomes birds live in, and it used a vari-
ety of approaches to validate its counts; an article published by
the Audubon Society called the result “a sobering picture” of wide-
spread avian decline. Grasslands were the hardest hit, with a doc-
umented loss of more than 700 million breeding individuals—a
decline of more than 50 percent. But major declines occurred in
every biome save one and in nearly every species. The net toll
amounted to nearly three billion individual birds, a figure that
sparked a campaign with tips on what people can do to save them.
(Top two: add decals to windows and keep cats inside.)
Given these data, it is tempting to conclude that despite the
brilliance of her writing, Carson did not succeed in protecting
birds. Moreover, the avian decline is part of a tremendous loss of
global biodiversity driven by human activity. According to the
Intergovernmental Science-Policy Platform on Biodiversity and
Ecosystem Services (IPBES), more than 40 percent of amphibian
species, almost 33 percent of reef-forming corals and more than
a third of all marine mammals are threatened. In all, biologists
estimate that more than a million species are at risk. This also
endangers human well-being, and the group notes that “we are
eroding the very foundations of our economies, livelihoods, food
security, health and quality of life worldwide.”
Still, the 2019 bird study, despite its grim results, also suggests
that protecting biodiversity (and thereby ourselves) is not a lost
cause. One important exception in the otherwise bleak picture its
scientists painted is wetlands (and the waterfowl that inhabit
them). There bird abundance increased 13 percent. What distin-
guishes wetlands from other ecological areas? One answer is that
wetlands have been especially shielded from excessive industrial
activity for a long time. The areas have been under a host of legal
protections on the federal, state and tribal level. Some of these
laws, such as Massachusetts’s powerful Wetlands Protection Act,
prioritized wetlands for their diverse ecological value. Others safe-
guarded such areas because they are important to navigation and
commerce, fisheries, flood control and water supplies. The 1899
Rivers and Harbors Appropriation Act, for instance, secured wet-
lands as parts of navigable waterways.
The other encouraging exception in the bird study was raptors,
a group that includes the majestic bald eagle. Raptor numbers have
increased by 15 million individuals. Bald eagles were on the verge
of extinction at the time Carson wrote, but they recovered in large
part as a result of the ban on DDT. A news story published by the
Audubon Society notes that “the numbers show that taking steps
like wildlife management, habitat restoration and political action
can be effective to save species.” Scientists have documented the
current threat to biodiversity. Their data also show that if we act
on this information, we can change the outcome.
JOIN THE CONVERSATION ONLINE
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or send a letter to the editor: [email protected]Paths to a Less
Silent Spring
We can still act on Rachel Carson’s pleas
to save biodiversity
By Naomi Oreskes