The broad topic of this column came to me from two readings. An article in “Science” reported that 3 billion birds in North America have disappeared since 1970, a decline of 30 percent. Virtually all types of birds have suffered these declines. Then there was the recent news that the monarch butterfly has been listed as an endangered species by the International Union for Conservation of Nature.

Of course, the question that immediately comes to mind is why? Why questions are basic to science. The scientific method is one of the most powerful ways humans have of knowing. But that methodology differs from arguments and inquiries in other walks of life.

Let’s start with a Major League Baseball player who is negotiating a new contract. His agent selectively goes through the player’s accomplishments, emphasizing the strengths and downplaying weaknesses. Meanwhile, the general manager of the team accentuates the player’s shortcomings and sells his accomplishments short. The participants from both sides are trying to prove their particular viewpoint.

The selective use of information to build an argument is found in many situations. Politicians on either side of the aisle cherry-pick data in support of a position or bill. Family squabbles or arguments among friends are other examples.

However, the method of science is fundamentally different. A scientist makes observations, such as declining numbers of birds, then develops a hypothesis (essentially an informed hunch) that might explain the pattern. Then the scientist collects data to try to disprove the hypothesis.

If the information collected does not disprove the hypothesis, that explanation is provisionally treated as true. Additional observations and experiments from different angles are done to try to knock down that hypothesis.

Only after multiple efforts to disprove a hypothesis is that explanation given credence. Even then, scientists realize that the jury is still out, and future experiments may well disprove the hypothesis.

So, scientists must be skeptics. The mode of scientific inquiry is to disprove hypotheses. Scientists accept a hypothesis as provisionally true, not because the scientist proved it but because he failed to disprove it. If you hear a scientist claimed he proved a hypothesis, he fails to understand the scientific method.

The scientific method avoids the problem of a phenomenon called confirmation bias. A scientist may have a clever hypothesis to explain some pattern in our world. But subconsciously, the scientist may downplay information that disproves the hypothesis and accentuate information that supports it. By trying to disprove the hypothesis, this bias is eliminated. We can feel confident about a hypothesis that has withstood multiple efforts to disprove it.

Now, back to the declines of birds and monarch butterflies. Following the United States’ ban on DDT in 1972, chemists and agronomists sought to develop insecticides for the protection of crops without affecting other insects and other animals. In 1999, a new class of insecticides called neonicotinoids were introduced.

Neonicotinoids (or neonics) are neuroactive insecticides, chemically similar to nicotine. The neonic named imidacloprid is now the most widely used insecticide in the world.

Neonics work well against sucking insects, some chewing insects and soil insects. In other words, agricultural pests. Initial work showed neonics have low toxicity in mammals.

Unfortunately, neonics affect other insects. Controlled experiments implicate neonics in the collapse of honeybee colonies and other pollinators. Bumblebee abundance is down by 90% in the last 20 years. Such insects are critical for most plants and virtually all crop plants. There is a certain irony here: neonics protect crops from herbivores but kill the pollinators that allow the crop plants to produce.

The European Union has been more proactive in responding to pollinator declines caused by neonics. The three most common neonics were banned in Europe in 2018. Several U.S. states have followed that lead.

An EPA statement published in August 2021 stated that 80% of the 1,445 endangered species in the U.S. are being negatively affected by neonics. This list includes plants, insects, birds, amphibians, and freshwater invertebrates. These results are based on hundreds of scientific studies. What are we waiting for?

For an excellent review of neonic impacts on birds, see the recent article by Scott Weidensaul, one of our most gifted nature writers, in the summer 2022 issue of “Living Bird” magazine.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu

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