[MCN] The rise of the Rockies "prepared" our mammals for ...

[Lance Olsen]

BROWN UNIVERSITY -- PUBLIC RELEASE: 3-JUN-2015

IMAGE: THE RISE OF THE ROCKIES EXTENDED FROM 
BRITISH COLUMBIA TO NEVADA IN THREE PHASES 
BETWEEN 56 AND 23 MILLION YEARS AGO. THE RISING 
MOUNTAINS DRIED OUT THE INTERIOR, PREPARING 
MAMMALS...
CREDIT: COURTESY OF ERONEN ET. AL.

PROVIDENCE, R.I. -- Paleontologists have 
documented how dramatic shifts in climate have 
led to dramatic shifts in evolution. One such 
event, the Grande Coupure, was a wipeout of many 
European mammal species 33.9 million years ago 
when global temperatures and precipitation 
declined sharply. What has been puzzling is that 
during the same transition between the Eocene and 
Oligocene periods, North American mammals fared 
much better. A new study explains why: the rise 
of the Rocky Mountains, already underway for 
millions of years, had predisposed populations to 
adapt to a cold, dry world.

'Regional tectonically driven surface uplift 
resulted in large-scale reorganization of 
precipitation patterns, and our data show that 
the mammalian faunas adapted to these changes,' 
write the study authors, including Christine 
Janis, professor of ecology and evolutionary 
biology at Brown University, in the Proceedings 
of the Royal Society B: Biological Sciences. 'We 
suggest that the late Eocene mammalian faunas of 
North America were already 'pre-adapted' to the 
colder and drier global conditions that followed 
the EO climatic cooling.'

The data in the study led by Jussi Eronen of the 
Senckenberg Research Institutes in Germany and 
the University of Helsinki in Finland, come from 
the authors' analysis of the fossil record of the 
two continents, combined with previous oxygen 
isotope data that reveal precipitation patterns, 
and tectonic models that show the growth of the 
Rocky Mountains. Specifically, the study shows 
that the rise of the range spread south in three 
phases from Canada starting more than 50 million 
years ago, down through Idaho, and finally into 
Nevada by 23 million years ago.

In the meantime, fossil mammal data show, 
precipitation in the interior regions dropped, 
and major shifts in mammal populations, such as 
an almost complete loss of primates, took place. 
Estimated rainfall based on plant fossils in 
Wyoming, for example, dropped from about 1,200 
millimeters a year 56 million years ago to only 
750 millimeters a year about 49 million years ago.

But across the region these correlated shifts 
occurred over tens of millions of years, leaving 
a well-adapted mix of mammals behind by the time 
of the Grand Coupure 34 million years ago.

In Europe, meanwhile, tectonic developments 
weren't a major factor driving local climate. 
When the global climate change happened, that 
continent's mammals were evolutionary sitting 
ducks. Other studies have already suggested that 
Europe's mammals were largely overrun and 
outcompeted by Asian mammals that were already 
living in colder and drier conditions.

Eronen said the findings should elevate the 
importance of collaboration across disciplines, 
for instance by integrating geoscience with 
paleontology, in the analysis of broad 
evolutionary patterns.

'Our results highlight the importance of regional 
tectonic and surface uplift processes on the 
evolution of mammalian faunas,' they wrote.

###
In addition to Eronen and Janis, the paper's 
other authors are C. Page Chamberlain of Stanford 
University and Andreas Mulch of the Senckenberg 
Institutes and Goethe University in Germany.

-- 
-------------------------------------------------------------------------------------------
"Localized ecological systems are known to shift 
abruptly and irreversibly from one state to 
another when they are forced across critical 
thresholds. Here we review evidence that the 
global ecosystem as a whole can react in the same 
way and is approaching a planetary-scale critical 
transition as a result of human influence."

Barnovsky et al. Approaching a state shift in 
Earth's biosphere. Nature.  Volume 486, 
Pages:52-58
Date published: (07 June 2012)
doi:10.1038/nature11018
------------------------------------------------------------------------------------------
Seeing the landscape for the trees: Metrics to 
guide riparian shade management in river 
catchments
<<http://onlinelibrary.wiley.com/doi/10.1002/2014WR016802/full>>
Authors:  Matthew F. Johnson, Robert L. Wilby
First Published:  27 May 2015

KEY POINTS:
*       Temperature over long stretches of river 
will not be affected by riparian shade
*       Midreaches of headwater streams are most responsive to riparian shade
*       To offset a 1°C temperature rise, 1 km of 
trees is necessary in UK small streams
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