Research Roundup: Mass extinction, older adult brains, plants in drought

June 8, 2020, 11:13 p.m.

Each week, The Daily’s Science & Tech section produces a roundup of the most exciting and influential research happening on campus or otherwise related to Stanford. Here’s our digest for the week of May 31 to June 6.

Mass extinction rate faster than previously thought

The world’s sixth mass extinction may be occurring at a much faster pace than previously thought, according to a study published on June 1 in “Proceedings of the National Academy of Sciences.”

In the past 100 years, scientists estimated that at least 543 land vertebrate species went extinct. Biology emeritus professor Paul Ehrlich and his team believe the same number of species will go extinct in the next two decades.

“When humanity exterminates populations and species of other creatures, it is sawing off the limb on which it is sitting, destroying working parts of our own life-support system,” Ehrlich told Stanford News. “The conservation of endangered species should be elevated to a national and global emergency for governments and institutions, equal to climate disruption to which it is linked.”

The researchers found that 515 species of land vertebrates were near extinction status, meaning fewer than 1,000 individuals of these species remain. They also found that half of all the species studied have fewer than 250 individuals remaining. The findings suggest endangered species are concentrated in the tropical and subtropical regions, where human activity causes most harm.

“It’s up to us to decide what kind of a world we want to leave to coming generations — a sustainable one, or a desolate one in which the civilization we have built disintegrates rather than builds on past successes,” Peter Raven, president emeritus of the Missouri Botanical Garden, told Stanford News.

Older brains similar to younger brains

For many older adults’ brains, the memory recall process parallels how young adults’ brains remember, according to a study published on May 29 in “eLife.”

“Some individuals exhibit remarkable maintenance of memory function throughout late adulthood, whereas others experience significant memory decline,” psychology postdoctoral research fellow Alexandra Trelle told Stanford News. “Studying these differences across individuals is critical for understanding the complexities of brain aging, including how to promote resilience and longevity.”

Researchers conducted memory tests in which participants learned to pair words with pictures of famous people and places, and researchers scanned participants’ brains when asked to recall pairings. 

The findings suggest stronger hippocampal activity and replaying patterns in the cortex are associated with better memory performance, regardless of a participant’s age. The hippocampus is a brain structure involved with remembering events.

“We’re beginning to ask whether individual differences in the ability to mentally travel back in time can be explained by asymptomatic disease that impacts the brain and predicts future clinical diagnosis,” psychology chair and professor Anthony Wagner told Stanford News. “We’re hopeful that our work, which requires rich collaborations across disciplines, will inform clinical problems and advance human health.”

During drought periods, plants use less water than expected

In the world where hot droughts will become more frequent, plants will intake less water than previously expected, leaving more water available for water sources, according to a study published on June 1 in “Nature Climate Change.”

The team analyzed a factor in climate models called evapotranspiration, which is the rate Earth’s land plants return water moisture back to the atmosphere.

“So much of the water balance in any given ecosystem goes to evapotranspiration, it has implications for how much water is left over for water resources for people,” earth system science assistant professor Alexandra Konings told Stanford Earth News. “It also has big effects on weather and climate.”

The findings suggest current climate models underestimate how much water plants will reserve in response to dry air, and overestimate the effects of dry soil on water retention in plants.

“Whether plants will fare better in future droughts is a more complex question,” earth system science postdoctoral research fellow Yanlan Liu told Stanford Earth News. “But now we know plants will use less water than expected.”

Contact Derek Chen at derekc8 ‘at’

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