Guest Post by Willis Eschenbach
“Out of passions grow opinions; mental sloth lets these rigidify into convictions”
Friedrich Nietzsche, 1844-1900
Anthony discussed the press release about the paper Past and ongoing shifts in Joshua tree distribution support future modeled range contraction. I didn’t have a copy so I wrote to the lead author, Kenneth Cole, to request one. He responded immediately and sent me a copy. My thanks to him, that’s science at its best. Other than the ritual obeisance to the climate models, the paper tells an interesting story about Joshua trees and the extinct Shasta ground sloths.
The Joshua “tree” is a cactus not a tree, it’s one one of the famous Yucca tribe of cacti spiny spiky things that aren’t cacti according to folks who know better than I do. Calling it a tree is merely the other cactus’s Yucca’s polite way to try to make it feel better about its funny appearance and desolate condition. It grows where almost nobody else can grow, in a very restricted climate range in the American Southwest. Not too hot, not too cold, not too much rain or too little rain, just right.
The fruit of the Joshua tree is a seed pod that was a favorite food of the Shasta ground sloth. The sloth appears to have been the only major seed dispersal mechanism for the Joshua tree. Which is hardly surprising, since other than pack rats and ground sloths, there’ve never been many herbivores hanging out where the Joshua tree grows. It’s way dry in that corner of the US.
The black stars in Figure 2 (from their paper) show the current location of Joshua trees, in and around the Mojave Desert in the hot Southwest.
Figure 2. The authors used rainfall and temperature maps to determine where Joshua trees might possibly grow, with green showing the most favorable climates. Map shows the lower parts of California (left) and Nevada (upper middle), along with a section of western Arizona.ORIGINAL CAPTION: … (A) Suitable climate model for Joshua tree created with mid 20th century (AD 1930 1969) PRISM mean precipitation variables and extreme mean monthly temperature events.
Now, to start with their map is interesting. I mean, the Joshua trees are certainly not growing extensively in what is the best part of the their range according to the authors. Unfortunately, much of the area they say is best for Joshua trees is on Nellis Air Force Base, so there’s no information for large areas. On the other hand, some areas with orange or even red (low probability) have a number of Joshua trees. However, nature is never as neat as we’d like it to be, and they’ve done well to generally outline the range by climate variables. And if it becomes desirable to plant Joshua trees, we know where they’ll likely grow.
Fifteen thousand years ago, in the days of the now-extinct Shasta ground sloth, the geological evidence from pack rat middens and sloth dung shows that the Joshua tree was much more widespread. However, humans happened upon the North American scene around that time, and converted all of the ground sloths into ground slothburgers and barbecued them. Which was bad news for the Joshua trees (not to mention the sloths), because no one else had much taste for Joshua tree seeds. As a result, the range of the Joshua tree is much reduced from its former glory.
The authors also show that the current range of the Joshua trees is further north, and at a higher elevation, than in the times of the ground sloth. During the last ice age the range of the Joshua tree extended across other areas that are now too hot or otherwise unsuitable to support them. As it warmed at the end of the ice age, the Joshua trees retreated (and advanced) to their current locations.
The problem is that without the ground sloths, the Joshua tree’s only seed dispersal mechanism is pack rats. The authors estimated the rate of spread from packrats at two metres per year. This seemed low to me, but is explained in the paper. The missing parts of the puzzle were a) unlike sloths, the packrats only carry the seeds a maximum of about forty metres or so to their homes, and b) the trees take twenty years to reach maturity and produce seeds. Result … 2 metres per year rate of spread. Always more to learn.
So far, so good. And if they’d quit there, it would have been an interesting paper. But no, they had to bring in the climate models. Now, climate models are notoriously bad at predicting precipitation (rain and snowfall). So they figured they’d pick the best of the bunch, viz:
Future downscaled GCM projections
To assess potential future changes in Joshua tree’s suitable climate space we compared future projections from several GCM’s for the late 21st century (2070 2099; ~2X CO2). Five individual models and one ensemble of 48 runs of 22 models based upon the A1B carbon emission scenario were obtained from the Program for Climate Model Diagnosis and Intercomparison (PCMDI; AR4) archive (available online). The five individual models used were: Hadley Center for Climate predic tion (Hadgem1), Max Planck Institute for Meteor ology (Mpi_echam5), CSIRO Atmospheric Research (Csiro_mk3), National Center for Atmospheric Research (Ncar_ccsm3), and Centre National de Recherches Météorologiques (Cnrm_cm3). They were selected because they represent a wide range of future moisture availability conditions for southwestern North America (Seager et al. 2007), and they all were ranked within the top half (of 22 models tested) for their ability to hindcast 20th century precipitation seasonality within the southwestern U.S. deserts (Garfin et al. 2010). These models, especially the Hadgem1 and Mpi_echam5, outperformed most models in replicating the 1950 to 1999 AD geographic distribution of average seasonal precipitation (Garfin et al. 2010).
Then, once they had what they figured were the best five models giving a “wide range” of rainfall results, they ran them and tried to figure where the Joshua trees might live in the future. The models gave differing results, so the authors defined a threshold for suitability (18%). If three of the five models said a particular gridcell would be above the 18% suitablity threshold for Joshua trees, they called it an “area of agreement for future suitable climate (AAFSC)”.
Then they show what those 5 models (and the 22 model ensemble) said would be suitable areas for Joshua trees in the years 2070-2099. Which all sounds vaguely reasonable until we look at their results in Figure 3 …
Figure 3. Results for five models (B-F) and 22 model ensemble (G). Pink areas with thin black outline show current range of the Joshua trees. ORIGINAL CAPTION: … (B G) The Joshua tree future suitable climate model runs for late 21st century (AD 2070 2099 AD): (B) Hadgem1, (C) Mpi_echam5, (D) Csiro_mk3, (E) Ncar_ccsm3, (F) Cnrm_cm3, and (G) Ensemble (44 runs of 22 GCMs).
See, if those results were mine, I’d throw up my hands and say “Not ready for prime time”. Those models are all over the map. They said they picked the models to “represent a wide range of future moisture availability conditions”, but I wasn’t expecting that huge a range. One model is “everything’s fine”, another is “they’re all gonna die!” That’s so wide as to be useless, and these are among the best models.
I don’t see any way that an average of those, or an “AAFSC” of those (area of agreement for future suitable climate), has any meaning at all. One of the models shows a wide area of hundreds of thousands of hectares where the Joshua tree could live, and another shows no suitable area at all.
Finally, once again we have the problem I have called “Models all the way down“. While the model results are interesting, they’ve skipped a big step. I want to see a map, just like the maps above showing possible future distributions of Joshua trees. But I want one showing how well the individual models (and the 22 model ensemble) did at hindcasting the current distribution of the Joshua trees.
I mean seriously – before showing us the model forecasts for 2070-2099 Joshua tree distributions, shouldn’t they show us the model hindcasts for the 1970-1999 Joshua tree distributions? It wouldn’t rescue the paper, but at least it might give some reason to think the selected models might be better than throwing darts at a map of the Mojave region.
Because without that, it’s just models disagreeing and quarreling with each other, all the way down …
w.
I wonder if they know that Y. brevifolia is commonly sold in landscape nurseries, and hort maps say it’s hardy zones 5-9….
It’s even sold in Florida retail nurseries…
…someone needs to tell them that it’s too delicate and needs very specific conditions and it won’t grow there /sarc
Willis Eschenbach says:
March 30, 2011 at 4:08 pm
Very nice read as usual Willis. A perfect example of models and ensembles at “work”! I always look forward to you posts.
On the topic of the image, It is not clear who owns the copyright on that image, the author or the subject, yes subject, not owner. You only own it if you own a hard copy. Copyright usually is the author’s unless a written or “implied” contract exists. I am a photographer so I routinely deal with copyright matters.
Also, the image in the subject’s site is the same as in the author’s, so it is entirely possible that the subject got it from there to begin with. I visited both the subject’s and the author’s website and neither claim a copyright.
You and the mods did the right thing as always of course, but not before we got a chance to see the the subject’s true colors. That made it all worth it for me :).
Thanks again!
Best,
Jose
Great opportunity for some keen green Johnny Joshuaseeds to get involved. Let them eat these seeds and dump in desired areas. Be a surrogate sloth to save the planet! Could catch on, especially for vegans who already appreciate a hearty sloth diet. It is possible that the sloth’s extensive digestive system prepared these seeds for germination but it seems worth a try, for the entertainment at least.
Of course, it is possible that the current catastrophic climate disruption will have unprecedented impacts on delicate feces ecology and that could doom this noble experiment.
So, perhaps it would just be simpler to get a Pied Piper to lead the packrats on longer journeys… or maybe not do anything at all.
I wonder if they consider humans like packrats. I mean if you google “Joshua Tree seeds” there are many reputable vendors, and some unreputable. So humans are spreading them now, internationally. Granted Joshua tree is very site specific and will not thrive where the vendors send most of their seeds to. But they are growing in Albuquerque via humans, and their future there is very questionable and remaining to be seen after the extreme cold temps in ABQ this winter, and if I recall I think it was pretty cold last winter too. The Needle Palm (or world’s most cold hardy palm) also had a sloth and a greater range in historical times, and is thought to be moved by glaciers to its current range which is Louisiana to South Carolina, and its pretty rare. But humans have spread it up past NY into New England, west to Colorado and British Columbia and into South America and to Europe and of course anywhere in the world where anyone would want one (back to the international seed vendors). And a warming climate would benefit them, as would wetter conditions since they are found near rivers and moisture for the most part. Global warming would increase their range I would think. But regardless of the AGW slant or not, the way plants range historically is a fascinating topic! And this was a very interesting post. I’m not sure that the average of the models is 100% useless, but I’m not sure the conclusions are accurate just because nature is so complicated.
Good thing we are combating climate change in the hopes of expand the Joshua tree’s range by puttin up vast arrays of solar panels in the Mojave…which will eliminate thousands of acres of the Joshua tree’s range.
*chases tail
@Willis Eschenbach
If the population of Joshua Trees are in decline you could always use that “trick” of yours we discussed the other day, to round up the figures , that should add a fue million trees. /JK
Interesting article as always.
Regards~
Good grief, Chris Clarke is quite the character.
Poked my head in at his blog and I won’t be going back there again. The folks are RC have better manners than him.
Re: latitude
“it’s too delicate and needs very specific conditions and it won’t grow there”
Your is very accurate. Check the nursery’s warranty on them lol Because they are sold does not mean they will thrive. But they may in fact thrive, anyone in a place like Florida with high atmospheric moisture would have to site accordingly in dry well drained soil or a raised bed. Then it would need to survive “long term” which is thought to be 20-40 years or so, facing the “30 year winter” or rain storms or whatever the climate and cultural differences in the sites. Culture does not mean human culture btw. But to say zone 5-9 is a real stretch. USDA temperature zones are designations for the one coldest night of the year averaged in a dataset (of years) so only one coldest night (one coldest temperature of the winter, only 1) of the year, averaged over a defined time period. Zone 5 can stretch from Maine to Ohio to Texas, Colorado, Idaho wherever without regard to precipitation, soil types, sun angle etc… so its not “hardy” to all of zone 5, but can survive zone 5 temperatures under very proper conditions for it which is very dry and very warm. Although it does experience fog and moisture in habitat, and this may help its adaptability in other places. But it is not thriving and widespread and most people fail at cultivating it successfully for short or mid term let alone long term outside of a very similar and suitable climate. USDA Zone 5 btw would mean on average it would see lows between -10 and -20 F
The USDA map changes periodically there have been several and what dataset of years they use becomes controversial at times not too unlike AGW, if you choose different years the map can move north or south. I think they are working on a new one right now that will be computer interactive with more variables included but I’m not sure.
Hindcasting… hmmm…
that’s all very well so long as you don’t alter past data to match what your model tells you happened…
but of course nobody would ever do that, would they. 😉
Kev-in-Uk says:
March 30, 2011 at 3:59 pm
No, it was properly directed here, the action was mine, and we were the ones who could (and did) respond immediately to his request.
Dunno …
Please, speculations about peoples motives are abhorrent. The most likely explanation is that he has a google alert set to the name of his blog, or he watches where the referrals to his blog are coming from. In any case, speculation is unwarranted and unwanted. I assume that Mr. Clarkes is acting in good faith until I see incontrovertible evidence otherwise. And to date I’ve seen no evidence of any kind, much less “incontroverible” evidence, that he was acting in bad faith.
Generally, I feel comfortable using anyone’s image as long as I cite it and link to it. This blog gets a lot of traffic. If I can drive some of that traffic to the website where the image originated, I think most people won’t have a problem with that.
For those that object, of course, as in this case, we remove the image immediately. I don’t fault Mr. Clarkes for making the request. I didn’t like the tone of his communication, and I objected to his accusations regarding the general factiness of this site, but he has every right to object to the use of the image.
w.
The hyperlink provided above, by the testy Chris Clarke, links to his blog.
On that blog he lists a a resume. On that resume there is a category labeled “Activism”.
It all makes sense now.
grzejnik says:
March 30, 2011 at 4:59 pm
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Re: grzejnik
The only reason they are not used more in landscaping is because they are so butt ugly….and nasty
AdderW says: “Next, watch out for well meaning humans relocating all Joshua trees in a sad effort to save them, resulting in an extermination instead.”
No, the Green philosophy calls for relocating the humans to save the trees, and extermination of the former is an acceptable alternative. (See the 10-10 video.)
Chris Clarke says:
March 30, 2011 at 3:14 pm
You’ve published that painting of my dog and me without permission either of the artist, Carl Buell, or the owner, yours truly. Please remove it.
Also – not that facts seem to matter much here – Joshua trees are not even moderately closely related to cacti, much less being cacti.
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lol, panties get in a wad often? Did you bother reading through the article? Other than the official classification of the non-trees, do you have any factual refutation of what was stated?
While these frequent drive-byes are often a source of humor for the many of us, I can’t help but be incredulous about the statements. “Fact’s don’t matter”. Ok, fine. Show people where they’re wrong. If you can’t, then it is simply a matter of projection. More, not only are you showing the world the alarmists intolerance of intellectual discourse, you’re showing the world the alarmists lack of capacitance for intellectual discourse. Don’t get me wrong, I enjoy witnessing the vapid vacancy, and I take comfort in the fact that for every commenter here, there many more readers. But every once in a while, it would be nice if the alarmists could display just a little cerebral capacity. It shakes my belief in my fellow man.
James
Reminds me of the El Nino models. Future forecasts say: Half say neutral to El Nino is on the way, half say neutral to La Nina is on the way. The average of all the model forecasts is highlighted. Huh????
Who is Chris Clark and why do we care what he thinks?
How long do the seeds stay viable ?
I.E. are dormant seeds lying all over waiting for the the right “climate”?
These maps include much of the Imperial Valley that has gone through a man-made water shortage in recent years.
Willis
Thanks for getting past the press release. After finding the study completely hidden behind a pay wall which is currently not even available in major universities (I tried CalPoly Pomona, UCLA, University of Arizona….), I was able to track down the taxpayer funded project which apparently paid for much, if not all of this work. It makes interesting reading:
http://sbsc.wr.usgs.gov/research/projects/sbsc.aspx
Also: http://biology.usgs.gov/ecosystems/global_change/packrat_middens.html
I remain convinced researchers would do well to pay more attention to recent changes before reaching firm conclusions about remote times. Example, which I commented on in the earlier post on Joshua Trees: Lake Cahuilla. Today’s Salton Sea has a surface area of about acres and evaporates an estimated 1.3 million acre feet a year. The top of the water is slightly over 200 feet below sea level. By contrast, Lake Cahuilla at maximum filling had an area of more than 2000 sq miles and a surface elevation well above sea level. It was six times as large as the Salton Sea and I find it hard to believe that it did not have significant effects on the surrounding climate.
The surroundings, of course, include the immediately adjacent Joshua Tree National Park:
http://books.google.com/books?id=a73tq1dXqYcC&pg=PA16&lpg=PA16&dq=salton+sink+prevailing+winds&source=bl&ots=V6N4YPOjc8&sig=n7R7bsyyWAADpRBs4h2w0Bzezg8&hl=en&ei=B2SRTdXKBYH6swO5m_y0Dg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBUQ6AEwAA#v=onepage&q=salton sink prevailing winds&f=false
(See p. 19)
We are gradually accumulating a well-dated record of recent high fillings, as late as the 1700s:
http://www.physorg.com/news/2011-02-lake-effect-theory-quake.html
The study area is in the dry bed of prehistoric Lake Cahuilla at Coachella, Calif. The lake has been dry since about 1715, according to timelines found in early travelers’ descriptions of the area. Researchers found that the lakebed was full of water six times in the study period.
“We now have the best chronology of these lakes that has ever existed,” said Weldon, who knows the area well from previous work.
This suggests the possibility of correlating these fillings with possible climate proxies in the region, including Joshua Tree distribution. (To be sure, the coming and going of Lake Cahuilla was so frequent and on such a short timescale, that any distribution proxy is highly improbable.) There is even the possibility of detecting the effects of the sudden formation of the Salton Sea in 1905, in the instrumental records of the COOP weatherstations of the area, though such effects would be much smaller than a high-level filling.
Willis Eschenbach says:
March 30, 2011 at 4:08 pm
As to the boy & dog picture—I’m sure it’s a good one or Richard would not pick it—but I say “good riddance to bad rubbish” about Chris’s attitude. There are plenty of great free & open pictures on the web. If Chris wants to play in this webspace, he better get ready to be a webspace player. If he doesn’t, well I hope the screen door doesn’t hit his a*s too hard on his way out. Well, maybe hard enough to leave an indelible weave pattern.
Okay, I’ve read the thread and the post. I have no idea what these seeds look like–color, diameter, shape, toxicity, density. How big are the pods? I’m curious. Perhaps Ken Cole could persuaded to provide a brief post giving a little more information. For instance, do birds eat the pods? I’m sure there are a number of interesting facts that he could provide that would clarify the thinking behind the article and put the final maps in perspective.
My first link (above) won’t quite get you there. From the linked page, click on Colorado Plateau Research Station, then on “Modelling Future Vegetation Change.”
OK, Salton Sea surface area should read 378 sq. miles.
Re the new Ground Sloth pic. It looks like she’s eating oak leaves. Any creature that ranges from oak forests to Joshua Tree deserts must be as well adapted as good old Homo Sapiens.
And the long link works if you replace the space between salton and sink with an underline.
Murphy was indeed an optimist.