Readers discuss grassland conservation and a hummingbird flight trick

Conservation considerations

The online mapping tool Landscape Explorer uses historical and modern aerial images to show how the American West’s landscapes have changed over the last 70 years, Brianna Randall wrote in “Landscape Explorer transports you back to a more wild West” (SN: 12/2/23, p. 32).

Randall wrote that Landscape Explorer has helped conservationists in Montana prioritize where to remove invasive trees that have taken root in grasslands, which threaten local biodiversity and increase the risk of catastrophic wildfires. Given the climate crisis, reader Mark Granville wondered why conservationists would cut down trees that help remove carbon dioxide from the atmosphere. Is grass better at trapping the greenhouse gas?

Though mitigating carbon emissions is key in combating the climate crisis, other ecosystem benefits like biodiversity, water storage, and people’s cultural and spiritual values remain important, says Kelsey Molloy, a rangeland ecologist at the Nature Conservancy, which is a member of the partnership that led the Montana efforts. That said, the role of grasslands and other rangelands in storing carbon is often overlooked, Molloy says. “Grasses store carbon deep in the soil, and that carbon is not lost from fires the way [it is] in treed landscapes.”

It’s a common misconception that planting more trees everywhere will decrease global warming, says Scott Morford,an applied spatial ecologist at the University of Montana in Missoula who led the development of Landscape Explorer. “In places like the Amazon, maintaining and increasing tree cover is critical for global climate regulation. In snow-dominated grasslands and shrublands, however, there is no clear evidence that increasing tree cover contributes to climate cooling,” he says.

Planting trees in historically treeless grasslands can also increase warming by altering the way the land surface reflects light back into space, Morford says. “In the northern Great Plains of the United States, tree cover would need to surpass 95 percent to achieve even a small net cooling effect.”

Previous simulations have even suggested that removing vast swaths of forests in the Northern Hemisphere and replacing them with grasslands may help cool the planet due to changes in the land surface’s reflectivity, Morford says. Of course, “no reasonable conservationist who values grassland protection would suggest cutting down North America’s northern forests to benefit the climate,” he says. “We are instead dedicated to safeguarding what little remains of the planet’s most endangered terrestrial biome and averting the collapse of its unique and essential biodiversity.”

As we seek solutions to the climate crisis, it’s important not to pit ecosystems and environmental challenges against one another, Morford says. “Rather, let’s unite to address the intertwined challenges of climate change and biodiversity loss in a way that preserves all the natural systems we cherish.”

Bird acrobatics

High-speed cameras reveal that Anna’s hummingbirds turn sideways to slip through gaps narrower than their wingspan, Erin Garcia de Jesús reported in “Hummingbirds show off a flight trick” (SN: 12/16/23 & 12/30/23, p. 14).

The story unlocked a memory for reader Blair Campbell: “Years ago, in my parents’ backyard, [which was] partially enclosed by a chain link fence installed to pen the little dog, I was fascinated to see a ruby-throated hummingbird take a weaving flight back and forth through the links.”

From the Nature Index

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