“Rainfall in the Sahel has dropped 20-30 percent in the 20th century, the world’s most severe long-term drought since measurements from rainfall gauges began in the mid-1800s,” said study lead author Patrick Gonzalez, who conducted the study while he was a visiting scholar at UC Berkeley’s Center for Forestry. “Previous research already established climate change as the primary cause of the drought, which has overwhelmed the resilience of the trees.”
The study, which is scheduled for publication Friday, Dec. 16, in the Journal of Arid Environments, was based upon climate change records, aerial photos dating back to 1954, recent satellite images and old-fashioned footwork that included counting and measuring over 1,500 trees in the field. The researchers focused on six countries in the Sahel, from Senegal in West Africa to Chad in Central Africa, at sites where the average temperature warmed up by 0.8 degrees Celsius and rainfall fell as much as 48 percent.
They found that one in six trees died between 1954 and 2002. In addition, one in five tree species disappeared locally, and indigenous fruit and timber trees that require more moisture took the biggest hit. Hotter, drier conditions dominated population and soil factors in explaining tree mortality, the authors found. Their results indicate that climate change is shifting vegetation zones south toward moister areas.
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  IMAGE:Rainfall in the African Sahel declined more than anywhere else in the world in the period of recorded measurements, causing increased aridity, as evidenced by this dust storm in Senegal.Click here for more information. |
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“In the western U.S., climate change is leading to tree mortality by increasing the vulnerability of trees to bark beetles,” said Gonzalez, who is now the climate change scientist for the National Park Service. “In the Sahel, drying out of the soil directly kills trees. Tree dieback is occurring at the biome level. It’s not just one species that is dying; whole groups of species are dying out.”
The new findings put solid numbers behind the anecdotal observation of the decline of tree species in the Sahel.
“People in the Sahel depend upon trees for their survival,” said Gonzalez. “Trees provide people with food, firewood, building materials and medicine. We in the U.S. and other industrialized nations have it in our power, with current technologies and practices, to avert more drastic impacts around the world by reducing our greenhouse gas emissions. Our local actions can have global consequences.”
Other co-authors of the study are Compton J. Tucker, senior earth scientist at NASA’s Goddard Space Flight Center, and Hamady Sy, country representative for Mauritania at the Famine Early Warning Systems Network.
Funding from NASA and the U.S. Geological Survey helped support this research.
If he’s identified a legitimate, wide-scale (continent-wide) phenomenon of trees moving south (equater-ward), it could be the ecotone shift that Fagan refers to in The Long Summer. Carole Crumley, an historical ecologist is the expert he cites. She claims ecotone shifts are the result in shifting latitudes of westerlies – the jet stream.
Pg 2 of:
http://anthropology.unc.edu/french/projects/climate/data_histclim/
The key to that region is, again, the ITCZ. That will hold the key to precipitation. Maybe not for Tunis but certainly for Sudan, Chad, Niger, Mali, and Mauritania. One thing that will be noticed is a change in SUMMER rainfall. It Tunis gets the majority of its rain in Winter, then that comes mainly from a European source and not tropical. Basically those would be fronts coming in from the Atlantic or down from Europe. During periods of pronounced global warming as we had some 9000 to 5000 years ago, they would get a lot of summer rain as the ITCZ was some 500km North of its current location in summer. If the planet were to warm up by 2 degrees, we would probably see a return of summer rains to the Sahara.
Also notice that the building of the Pyramids in Egypt and the Ziggurats of Mesopotamia start right as the climate is undergoing a change and both areas were starting to experience major drought which they had not seen in some 5000 years previously in those locations. I can’t help but wonder if those were not designed to appeal to the gods for rain in addition to being tombs and temples. People can become very superstitious when things change dramatically.
It has happened time after time after time and is quite well documented in geological papers of things such as pollen surveys of ancient lake bed. You see the pollen change from forest trees to grasses and back again. It has to do with migration of very significant weather patterns that generate a shipload of rain. This isn’t anything “new” or anything caused by man, in my opinion. It is just one more episode in a long string of similar episodes.
I really get tired of this environmental narcissism where people assume humans control everything about the planet and are the cause of all problems and can “fix” everything or even have a measurable influence on it. There are just some things that go on in this universe that man has no control over.
“The researchers focused on six countries in the Sahel […] at sites where the average temperature warmed up by 0.8 degrees Celsius and rainfall fell as much as 48 percent.”
Are there any other sites in the Sahel as well, and if so, what kind of sampling is that ?
That assumes that there HAS been any measurable impact from human GHG emissions and I would AGAIN point back to the 1910 to 1940 warming and ask you how greenhouse emissions could possibly have caused that warming when there wasn’t any significant increase in greenhouse emissions and why you think the late 20th century warming which was of practically identical duration and rate WAS caused by greenhouse emissions.
Just because the two graphs (CO2 rise and temperature change) coincide for a single 30 year period in the record DOES NOT mean that one causes the other because the two diverge or go in opposite directions for a much greater portion of the record.
As someone else posted, you are entitled to your opinion but you are not entitled to your own set of facts. The facts are that over the past 150 years there has been no overall correlation between temperature and greenhouse emissions. Your position is based on a “belief” or a “feeling” not on facts.
I thought it was called the Sahara forest before Paul Bunyan cut all the trees. Hey, my folk story is as good as these researchers’ fiction.
They do attribute remarkable powers to “we in the U.S. and other industrialized nations”. Not only can we seemingly change the climate and change it back again, but we have an infinite source of dollars to draw upon to do so. Wow. I guess little things like millions struggling to find jobs and pay their mortgages, millions with little or no health care, poverty, homelessness, etc. really don’t matter after all. We just need to look at the Big Picture and save the planet. When you look at it the “right” way, everything just falls into place. sarc/off
Well, they do have to consider their funding, I suppose.
Garrett conveniently forgot to mention how much arable land there would be in Canada if the Earth warmed even slightly.
O/T having read the post prior to this one by Shub Niggurath I am concerned his post was removed because of “inflamed reactions”. Can’t see the problem frankly. The post made an important contribution to the debate. What should have been removed was the “inflamed reactions”. A very bad precedent has been set which bodes ill for the future. The poor behaviour at the core of the Climategate emails is now creeping into this site.
Luckily, I’m free to think what I like and I have the internet.
Gibby says:December 12, 2011 at 8:59 am
Steve Keohane says:[…]
Steve-Gonzalez is referring to the fact that Ponderosa Pines need a given amount of water in able to naturally prevent the bark beetles from eating through its thick bark and ultimately killing it.
While that may be true, the trees are always stressed from lack of water. It is abnormal to receive any rainfall during June and most of July here, which kind of puts a damper on the growing season.
Smokey: First off, you seem to agree that increased CO2 will result in warming. At least we’re on the same page there.
Second, you assume way too much. Many scientists do realize that warming could be beneficial to some areas, but it’s very difficult to predict with certainty what areas will benefit and by how much. Even an expert in biosphere science would be hard-pressed to give an answer to that question, so I’m not so sure why you’re so confident in your predictions.
You also assume that plants and humans will be able to adapt rapidly (within a couple of generations I presume) to such changes. This gets right to the crux of the issue – humans, animals and plants need time to adapt to changes. The main problem with GW is that it’s expected to occur too quick for many plants and animals to have time to adapt.
There is not “insufficient” CO2 in the atmosphere. There’s no such thing as the right amount of CO2. The closest thing to a “right” amount would be one that is stable or changes very slowly over time so that humans and other living creatures have time to adapt.
Comparing me and others to “eugenicists” and “eco-fascists” is just plain silly. I’m trying to have a reasonable discussion, but with remarks like that I begin to wonder whether I’m just wasting my time. If was silly enough I could retort with similar remarks, but that gets us nowhere.
Joe Crawford says:
I apologize if my referencing of a paper from an online journal that summarizes the subject from approximate 65 peer reviewed papers doesn’t meet your standards. Might I suggest that if you question the validity of the my reference, and consider it cherry-picking on my part, you might go read the 65 papers that it summarizes. You might also re-read the Olssen paper since it references conditions in the Sahel as far back the 1930s
I never disagreed with the results of that paper in the first place. It could have referenced 200 papers and my argument would still be the same: the Olssen paper refers to greening over roughly a 25 year period, whereas the article above refers to a period nearly twice that length. If one was to objectively pick a period for purely statistical purposes, then the longer period would be more appropriate.
Yes, the Olssen paper talks about conditions as far back as the 1930’s. What’s your point? It mentions it in an historical context, not in the context of greening.
I do agree that the Sahel has greened recently. An interesting point about that Olssen paper you referenced is that much of the research comes from climate scientists, and that GW is responsible for the increased rainfall. Some of the data (Fig. 1 in that article) even comes from the Climatic Research Unit, University of East Anglia. So I presume this means that you accept the validity of both mainstream climate science and the data of the CRU?
Certainly trees need water to grow but why blame CAGW when we know that CAGW is not happening. Climate change carries on as does weather changes but the drivers are the AMO, PDO etc not man.
This is a nonsense piece of work,
December 12, 2011 at 9:27 pm
Gibby says:December 12, 2011 at 8:59 am
After reading Willis’ piece on the Sahal, I discover it receives as much or more rain than Colorado, which only strengthens my point.
Garrett, this statement makes the whole Gonzalez paper junk: “We in the U.S. and other industrialized nations have it in our power, with current technologies and practices, to avert more drastic impacts around the world by reducing our greenhouse gas emissions. Our local actions can have global consequences.”
How can any reasonable person write that based on the few years studied? The paper used data from 1954 through 2002. A later paper, cited by Joe Crawford, used data from 1980 through 2008. The paper cited by Crawford shows the Sahel is greening, and the period studied encompasses the last 22 years of the Gonzalez paper. What these two studies show is that the drying and greening of the Sahel may be cyclical. Nothing more.
Garrett says:
December 13, 2011 at 12:43 am: [ … ]
Don’t misrepresent my position, which I’ve stated many times here. I have been entirely consistent. Here is a summary of my position:
At current and projected concentrations, CO2 is harmless, and beneficial to the biosphere. More is better; there is no downside. CO2 probably results in some insignificant warming, but other factors have a greater effect. A warmer planet is a net benefit to humanity. Cold kills.
I will be happy to discuss any of those statements, and back up my position with plenty of citations like this. The biosphere evolved in much higher CO2 concentrations, at times when life on earth flourished. There is no evidence of global harm due to the rise in anthropogenic CO2, nor from the increase in CO2 in general. Therefore, CO2 is harmless, QED.
The unscientific alarmism over “carbon” is simply a disguise for the massive, organized, global scam that is intended to lead to immense tax increases and the transfer of our wealth to/through the thoroughly corrupt UN, and which will do nothing measurable regarding global temperatures.