(This is the first paper Cooper has led since he was fired from the University of Adelaide in December 2019 for misconduct, allegations which he has denied.) Kauri trees (one shown) have grown in New Zealand for thousands of years. Cooper and his colleagues obtained cross-sections from four ancient trees recovered from a swamp at NgВДЃwhДЃ Springs in northern New Zealand, and analyzed them for carbon-14, a radioactive form of carbon. The countryвЂ™s swampy bogs preserve the relics of kauri trees dating as far back as the Laschamps excursion. One reason for that belief is a dearth of precise dates for the timing and duration of the geomagnetic event to correlate with environmental, ice core and magnetic rock records.Д®nter New ZealandвЂ™s kauri tree, among the most ancient in the world. In fact, вЂњthe general belief had been that geomagnetic changes had no impact on climate or anything else,вЂќ says Alan Cooper, an evolutionary biologist at BlueSky Genetics in Adelaide. So some researchers have suggested that these flip-flops may be linked to extinction events ( SN: 11/19/20).Д«ut evidence for this has proven elusive. 19 Science.Дuring a reversal, EarthвЂ™s protective magnetic field, which shields the planet from a barrage of charged particles streaming from the sun, can lose strength ( SN: 1/28/19). ItвЂ™s the first study to directly link a magnetic pole reversal to large-scale environmental changes, the team reports in the Feb. With the help of new, precise carbon dating obtained from ancient tree fossils, the researchers correlated shifts in climate patterns, large mammal extinctions and even changes in human behavior just before and during the Laschamps excursion, a brief reversal of the magnetic poles that lasted less than a thousand years. A flip-flop of EarthвЂ™s magnetic poles between 42,000 and 41,000 years ago briefly but dramatically shrank the magnetic fieldвЂ™s strength - and may have triggered a cascade of environmental crises on Earth, a new study suggests.

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