When dinosaurs disappeared, forests thrived
Rainfall patterns remained largely unaffected despite dramatic climate
changes

Date:
December 16, 2020
Source:
McGill University
Summary:
To understand how specific ecosystems were affected by a large
asteroid impact that led to the mass extinction of dinosaurs, a
team of scientists has analyzed the microscopic remains of plants
from this period. They found that local plant communities and
ecosystems experienced a long-term shift towards fewer aquatic
plants and an increase in terrestrial plants, including trees
such as birches and elms. Changes in rainfall patterns during the
extinction event were relatively minor and short-lived.



FULL STORY ==========================================================================
It's known that the primary cause of the mass extinction of dinosaurs,
about 66 million years ago, was a large asteroid impact. But the exact mechanisms that linked the impact to mass extinction remain unclear,
though climactic changes are thought to have played a part.


==========================================================================
To understand how the mass extinction and associated climate changes
affected specific ecosystems, a team of McGill scientists has analyzed the microscopic remains of plants from this period, found in the sediment of
rivers in southern Saskatchewan. In a recent article in Palaeogeography, Palaeoclimatology, Palaeoecology they show that in this area, local plant communities and ecosystems experienced a long-term shift towards fewer
aquatic plants and an increase in terrestrial plants, including trees such
as birches and elms. The researchers speculate that this increase was
due to the extinction of large plant-eating dinosaurs. They also found, unexpectedly, that changes in rainfall patterns during the extinction
event were relatively minor and short-lived.

"This could be important as we look to the future of global warming,
where many scientists have predicted that changes in precipitation
could have big impacts on humans and ecosystems," says Peter Douglas
from McGill's Department of Earth and Planetary Scientists and senior
author on the paper. "At other times of major climate change in Earth's
history we typically do see evidence for such changes. The absence of
such a signal during the most recent mass extinction event is intriguing." Douglas adds, "Surprisingly, scientists know more about what happened in
the oceans at the end-Cretaceous extinction than on land. By clarifying
the environmental changes occurring during this period, we narrowed
down the factors that are likely to have caused the disappearance
of dinosaurs. The research also provides an important analogue for environmental changes humans are causing to the planet, and the potential
for future mass extinction."

========================================================================== Story Source: Materials provided by McGill_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Robert D. Bourque, Peter M.J. Douglas, Hans C.E. Larsson. Changes in
terrestrial ecosystems across the Cretaceous-Paleogene boundary
in western Canada inferred from plant wax lipid distributions
and isotopic measurements. Palaeogeography, Palaeoclimatology,
Palaeoecology, 2020; 110081 DOI: 10.1016/j.palaeo.2020.110081 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201216113240.htm

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