Decline of desert tortoise in Joshua Tree linked to long droughts

Cowboy_Ken

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http://www.latimes.com/science/scie...change-20131213,0,5298051.story#axzz2o34oz92P




In recent years, California's Agassiz's desert tortoise population has been decimated by shootings, residential and commercial development, vehicle traffic, respiratory disease and predation by ravens, dogs and coyotes.

Now, dwindling populations of the reptiles with scruffy carapaces and skin as tough as rhino hide are facing an even greater threat: longer droughts spurred by climate change in their Sonoran Desert kingdom of arroyos and burrows, according to a new U.S. Geological Survey study.Drought conditions are linked to declines in a population of desert tortoises in a square-mile study plot in Joshua Tree National Park, according to the study published in the online journal Biological Conservation.The study, one of the few to examine a desert tortoise population's response to climate change, surveyed about 1.4 generations of the species scientists know as Gopherus agassizii."The last time the climate of the Earth jumped as rapidly as it seems to be now was about 55 million years ago - and that was a five-degree increase over thousands of years," Jeff Lovich, lead researcher of the USGS team, said in an interview. "The changes we are seeing now are virtually unprecedented, and they are occurring in a desert landscape fragmented by development and roads.""The desert tortoise is surviving in the current landscape by its toenails," he said."Although the animal's name suggests that it is well adapted to desert conditions, it is not," Lovich said. "Prior to 7,000 to 10,000 years ago, the region was cooler and wetter with lakes fringed with Joshua trees and junipers. That's the landscape that dominated the evolutionary history of the so-called desert tortoise.""It probably evolved its burrowing trait to escape predators," he said. "Later, burrows became a critical means of escaping the climate extremes.""So, this animal has 'accepted' - not adapted to - desert conditions," he said. "Our study shows that its survival can be seriously compromised after two to three years of drought."Desert tortoise survival rates in the study plot were found to be highly dependent on climate events, particularly the duration of droughts. For example, the study said, the adult population of about 175 to 200 tortoises declined to about 25 tortoises from 1996 to 2012, a period concurrent with drought conditions in the area.The postures and positions of a majority of dead tortoises found in 2012, it said, were consistent with death by dehydration and starvation.Some live and many dead tortoises found in 2012 showed signs of predation or scavenging by carnivores.The problem, Lovich said, may be linked to drought conditions, which killed off annual plants and triggered a crash in populations of rodents that eat them. As a result, coyotes, which normally thrive on kangaroo rats and rabbits, turned to the lumbering tortoises for sustenance.The study acknowledges that the tortoise population survived through the 1960s and 1970s, which appeared to be relatively dry years, then increased dramatically during later periods of greater precipitation."However, if drought duration and frequency increase," it said, "they will likely have wider and more significant impacts on Agassiz's desert tortoise survivorship, particularly in the low Sonoran Desert portion of their range in California, and it will be difficult or impossible for resource managers to mitigate their effects."The study of the desert tortoise, which is protected under the U.S. Endangered Species Act as threatened in portions of Arizona, California, Nevada and Utah, was funded by the U.S. Bureau of Land Management.
 

BeeBee*BeeLeaves

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Very depressing, if true.

I no longer believe these completely because studies funded by the government are usually done to lobby and steer funding to that agency. A politician told me that. That whole "never let an emergency go to waste" philosophy. Or as he put it, "milk it for all its worth".

Sigh.


I do find the adaptation part of the study right on with what my grandpa used to tell us that desert tortoises are shade animals, using only the sun long enough to bring their temps up for digestion, other than that they are smart animals who love and enjoy their shade. The desert being much cooler long ago .. their evolving with the warmer ... fascinating, already known by common sense people.

I have to ask myself if this is all in order to get funding to offset the lack of funding in Nevada. Call.Me.Jaded. Thanks for sharing Cowboy Ken! : )
 

BeeBee*BeeLeaves

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Here was a disputing comment made about that article. The referred to sites are interesting also:

forparity at 5:41 PM December 17, 2013

“The last time the climate of the Earth jumped as rapidly as it seems to be now was about 55 million years ago — and that was a five-degree increase over thousands of years,” Jeff Lovich, lead researcher of the USGS team, said in an interview. “The changes we are seeing now are virtually unprecedented, and they are occurring in a desert landscape fragmented by development and roads.”
Wow - "jumping climate?"

Difficult to imagine how people like this are allowed to simply fabricate such wild nonsense about the earth's climate - and the so called "journalist," simply prints it, without considering the need to challenge it? The earth has been warmer than present several times during the past 9,000 years, and more than 3 degrees C warmer during the Eemain period (about 120K years back).

The big "jump" in temps came as we exited the last great ice age about 10K yrs back - an 11 degree C "jump."

Here's the nearest GISS temp chart to Joshua I could find:

http://data.giss.nasa.gov/cgi-bin/gistemp/show_station.cgi?id=425000422390&dt=1&ds=14
. . and the SW region of the US precipitation trend over the past 100 yrs+

http://www.ncdc.noaa.gov/cag/time-s...ase=10&firsttrendyear=1895&lasttrendyear=2012

I'd suggest that a journalist and a lead researcher for the USGS should be let go. (Said the comment writer, forparity)


Whoa Nelly, on this one, which is more likely what is truly happening to the desert tortoises, to our chagrin, both as tortoise lovers and as taxpayers:

straightspeaking at 9:23 AM December 14, 2013

The wind and solar farms are destroying tens of thousands of acres of habitat and they are expanding daily. Further all the vehicle and heavy equipment traffic on the thousands of miles of wind turbine maint. roads kills tortoises every day.

My work brings me to wind-farm country quite often and I have spoken with many wind-farm employees over the past few years. Without exception they speak of the following;

1. The ridiculous costs and subsidies borne by the public.
2. The high maint. costs and short life spans of the turbines.
3. The dead bird/animal clean up crews that pick up the dead and dying every morning.
4. The very small amounts of very expensive, usable power produced for the amount of land consumed.
5. Even the engineers wink and laugh about the absurdity of wind power. And sheepishly admit they are thankful that Romney wasn't elected and that the subsidies continue.
6. Wind companies will not provide accurate figures regarding power generated, birds and animals killed or actual cost of generation. Contact WEA and see how much good, accurate info you can get.
7. The common joke is, "Hey, when we're done building these things and they finally figure out they're worthless - the government will pay us again to tear them out and restore the land."

The renewable energy scam is a national tragedy - a cancer upon the land. (Said the comment writer, straightspeaking)
 
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