Readers discuss net-zero carbon emissions and glass frogs

For good measure

Cutting carbon dioxide emissions to curb climate change and reach net-zero is possible but not easy, Alexandra Witze reported in “The road to net-zero” (SN: 1/28/23, p. 22).

A report by Princeton U­niversity’s Net-Zero America project, released in 2021, estimates that wind and solar power production needs to roughly quadruple by 2030 to achieve the United States’ goal of net-zero carbon emissions by 2050, Witze reported. In the most ambitious scenario, “wind turbines would cover an area the size of Arkansas, Iowa, Kansas, Missouri, Nebraska and O­klahoma combined,” she wrote.

Reader Mary Sweeney noted that, while technically correct, the statement quoted above could be misleading. “What the Princeton report actually states is that the visual footprint of the turbines would be equivalent to the combined areas of the states listed above. In other words, that figure for land use was reached by considering the very large area from which the very tall turbines would be visible,” Sweeney wrote. The actual land use would be only a tiny fraction of the visual footprint.

Disappearing act

A glass frog hides nearly all of its red blood cells in the liver while it sleeps, upping the animal’s transparency, Susan Milius reported in “Glass frogs make their blood vanish” (SN: 1/28/23, p. 6).

Reader Len Yaeger wondered what criteria the researchers used to determine transparency in the frogs.

Biologists think about transparency a bit differently from physicists, says Jesse Delia of the American Museum of Natural History in New York City. “If the individual tissues are transmitting over 90 percent of light, they’re — as far as biology goes — relatively perfectly transparent,” he says. Glass frogs’ green dorsal skin “gives them sort of a diffuse transmittance, like the filtered light if you were to look up at the tree canopy on a sunny day.”

What’s more, the translucence of glass frog skin appears across a continuum. The clearest see-through skin is on the belly, which helps explain why it took Delia some years to notice the cell-hiding phenomenon in sleeping frogs. Delia had often seen the frogs sleep in the wild, their less-translucent backs facing outward as the frogs clung to leaves. “It wasn’t until I saw them sleeping in captivity on glass that I could actually see their bellies,” he says. From there, “you can see straight in to their organs.”

Since the frogs can pack their red blood cells together without forming clots, reader Mara Chen-Goldberg wondered, could the discovery aid research into blood clot treatments for humans?

Many people are asking the same question, Delia says. The frogs seem to somehow inhibit the typical vertebrate blood-clotting process. “But at this point, we don’t know whether that mechanism would be directly translatable to human medicine,” he says.


A cunning fox catches fish, stunning researchers” (SN: 11/5/22, p. 4) incorrectly stated that fishing in foxes had not been observed before. While the study featured in the story describes the first record of a red fox fishing, a 1991 study published in Polar Research had previously reported fishing in arctic foxes in Greenland. This incorrect fact also appeared in a year-end roundup in Science News’ December 17, 2022 & D­ecember 31, 2022 issue.