The following commentary was published by The Daily Progress, the daily newspaper of Charlottesville, Virginia, on September 24, 2024. You can read it at the newspaper’s web site (by clicking on the web address below), or you can read the unedited (original) version posted here below the link.

https://dailyprogress.com/opinion/column/marlene-a-condon-bad-science-results-in-bad-environmental-outcomes/article_3d570250-791d-11ef-8952-afc030209d81.html

Bad Science Results in Bad Environmental Outcomes

You can take a Carolina Chickadee out of the forest, but you can’t take the forest out of this bird. A flawed study unintentionally verified just that. 

 

 ALL TEXT AND PHOTOS © Marlene A. Condon

A serious problem for the environment nowadays is the scholar- and media-driven promotion of peer-reviewed scientific studies that do not actually prove what they purport to establish.

 

The result is an unknowing public being led to follow the erroneous dictates of careless scientists, creating, in the end, more difficulties for our ailing natural world.

 

A prime example is the current widespread narrative that “nonnative plants reduce habitat quality for insectivorous birds”. This quote from a now-famous chickadee study by Drs. Desirée L. Narango, Douglas W. Tallamy, and Peter P. Marra overgeneralizes their results that, in fact, only apply to the Carolina Chickadees they observed and other similarly forest-dependent bird species. In other words, the scientists have made a statement that is more universal in nature than is justified by their available evidence.

 

https://www.pnas.org/content/115/45/11549

 

This indiscriminate declaration has served as the keystone argument to encourage land managers to prioritize growing native-plant species on properties by first removing so-called invasive, non-native species. Additionally, it has convinced other scientists, the media, government officials, environmentalists, and even individuals to disseminate these ideas far and wide.

 

However, this entire study is based upon a flawed premise; its results are therefore not valid; and no action should be taken based upon the scientists’ recommendations.

 

For scientific findings to be considered sound, researchers must follow protocols (an official system of rules) known as the Scientific Method.

 

First, they make an observation: In this case, that some insectivorous-bird populations are decreasing.

 

Next, they ask a question: Could human-dominated landscapes containing an abundance of alien plants that don’t support many leaf-feeding insects that birds eat be the cause of this situation?

 

And third, the scientists design a study that will enable them to collect data that they can then examine to determine the answer to their question.

 

The flaw in the chickadee study occurred before researchers left the building and got out into the field. The senior scientists—one of whom was Smithsonian ornithologist (bird authority) Peter Marra —inexplicably chose the Carolina Chickadee, a forest bird, as the avian species they would study in suburbia, which is typically more akin to field habitat.  

 

If people (and their associated developed areas) did not exist, a chickadee would be found only in forest because it nests in natural tree cavities. And because it occupies that kind of niche (the physical space that makes possible survival and reproduction of a species), it has evolved to feed upon the insects closely associated with the large native trees that comprise forest.

 

In other words, the life of a chickadee is tied forever to large native trees, so any area without an abundance of these specific plants—as is the case in much of suburbia—would be regarded as inferior habitat.

By performing their study in sub-optimal habitat, the three scientists reached a foregone conclusion: A chickadee’s reproductive efforts will be sub-optimal (fewer healthy chicks) in yards devoid of numerous large native trees.

 

A legitimately done study would have looked at avian species living in suburbia without human-supplied assistance, such as the feeders and nest boxes that encourage chickadees to try to reproduce under less-than-desirable conditions. Native birds of field and edge (where field meets forest) habitats, such as the cardinal, wren, catbird, dove, jay, mockingbird, and many others, are common and could have been studied quite easily.

 

The researchers could have compared how well these species were able to reproduce in yards with a higher percentage of nonnative plants versus yards with a lower percentage to see if it truly made a difference. Of course, as any birdwatching person living in an urban/suburban area realizes, the birds living and reproducing there do quite well among the mix of native and nonnative plants.

 

Urban-/suburban-adapted birds feed upon a host of insect species, unlike forest-dwelling birds, such as the chickadee, many kinds of warblers, and other species that are more tied to leaf-feeding caterpillars and sawfly larvae found in large trees.

 

It's unfortunate that so many people have been so fooled by this study. Thanks to Drs. Narango, Tallamy, and Marra, a great deal of perfectly functioning habitat has been, and will continue to be, destroyed—often with the application of herbicides that not only harm wildlife in the area, but can poison the ground and water.

 

It will take years for viable habitat to replace it—precious time our wildlife can’t afford—and there’s absolutely no guarantee, either, that it will consist of native plants.

NATURE ADVICE:

Just because a scientific study by people with “Ph.D.” after their names is peer-reviewed doesn’t mean it cuts the mustard. Always scrutinize what scientists say to be sure their arguments are logically sound.

DISCLAIMER:

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Missing the Forest for the Trees

A male Eastern Towhee perches on a radio tower enveloped by an Autumn Olive shrub—perhaps the best wildlife plant there is as it feeds numerous species of pollinators, birds, and mammals.

ALL TEXT AND PHOTOS © Marlene A. Condon

 

There’s much publicity nowadays that misinforms people about the need to create a wildlife habitat in which 70% of the plants are native. A major focus is often on getting folks to grow trees—in particular, oak trees. Why? According to Nancy Hazard, a member of a group called “Greening Greenfield [Massachusetts]”, “Oak is king. Oaks host over 400 different species of moths and butterflies.”

 

https://www.recorder.com/Ecological-difference-39423618

 

This deceptive “fact” (which comes from entomologist Doug Tallamy, whose tally for caterpillar species that feed on oaks was 557 in 2017, according to the National Audubon Society) is repeated often in gardening columns, making people think that any oak they grow in their yards is going to feed hundreds of species of moth and butterfly caterpillars.

 

https://www.audubon.org/news/new-research-further-proves-native-plants-offer-more-bugs-birds

 

The reality, however, is that this number represents the sum of Lepidopteran species that feed upon the entire genus of oaks across the country, of which there are at least 90 species. In other words, if you plant a White Oak (Quercus alba) in your yard, it’s not going to feed nearly as many caterpillar species as you might think.

 

Why the focus on tree-caterpillar species anyway? The study that supposedly proved that at least 70% of the plants in a yard should be native for the benefit of songbirds was based upon the foraging habit of Carolina Chickadee parents getting food for their chicks. These small birds mainly feed their young tiny caterpillars that they find on forest trees (their ecological niche) which, by definition, consists of native species.

 

Although Doug Tallamy and his coauthors, student Desiree Narango and ornithologist Peter Marra, concluded in their original paper that the Carolina Chickadee requires native trees (which should have been obvious even without a study) to reproduce successfully, their observations are now employed by virtually every garden columnist and TV gardening personality to mean all bird species require 70% of the plants in people’s yards to be native. But this contention was not proven by the study everyone references, and therefore Narango, Tallamy, and Marra should have set the record straight by now.

 

https://indefenseofnature.blogspot.com/2020/10/a-carolina-chickadeegrasps-tulip-poplar.html

 

However, these scientists do not seem to comprehend or value the larger picture because they are so focused on only a fraction of it. They’ve been missing the forest (the rest of the environment) for the trees (especially those oaks).

 

Dr. Narango “believes that her results provide convincing evidence that planting native is in a bird lover’s best interests. ‘The trees [our color-banded chickadees] were going to were covered in warblers, tanagers, and orioles,’ she says. ‘They’re basically telling us what these other birds want.’”

 

https://www.audubon.org/news/new-research-further-proves-native-plants-offer-more-bugs-birds

 

Yes, the chickadees were telling her what warblers, tanagers, and orioles want because these species are birds of the forest, as is the chickadee. To assist such birds requires that your yard and every yard around you must become forest, something highly unlikely to occur in urban/suburban areas.

 

Additionally, this newly minted scientist fails to recognize that the forest habitat of these species is not what all other birds want. If everyone made their yards forestland, we’d lose our common backyard species—Eastern Towhee, Northern Cardinal, Brown Thrasher, and Song Sparrow, to name a few—that require shrubby habitat, not forest. Sunny shrubland with herbaceous plants and woody shrubs supports far more diversity of insect life than forest, including an abundance of mammal, reptile, salamander, and bird species. And truth be told, numerous nonnative shrubs and herbaceous plants support these organisms very well.

 

https://www.marlenecondon.com/

 

For the greatest diversity of life forms, our landscape cannot consist solely of forestland, which is what Tallamy, Narango, Marra and their followers are pushing for, even though they don’t seem to know it.

 

NATURE ADVICE:

If most of your plantings are already native species, that’s great—if they provide the proper structure necessary to create good wildlife habitat. Problems arise when people feel they are obliged to get rid of fully mature nonnative plants, especially by way of pesticides, even though the resulting bare ground or young (immature) newly planted native plants will not be useful for a long time to come.

Alien plants can provide habitat for shrubland bird species, whether it be by providing nesting sites, food (fruits/seeds), or cover. It’s a huge mistake to destroy habitat that functions perfectly for shrubland birds. Please don’t be swayed by the harmful information perpetuated not only by the media, but also scientists who dare not speak against a popular thought, even though it is wrong.