If you cut your forest, the winds will not blow from the ocean and will not bring you rain. Natural forests draw atmospheric moisture inland from the ocean in a positive feedback loop. This builds up precipitation inland, compensating for water lost through river flow and ultimately increasing river runoff due to the sustained low pressure area inland. Forests make rivers.
A 200-year-long drought 4,200 years ago may have killed off the ancient Sumerian civilization, according to Matt Konfirst, a geologist at the Byrd Polar Research Center
Thanks largely to the mainstream obsession with ‘climate change’, research into historical disasters that focuses on climate is getting more funding. Mainstream reporting of this research is skewed towards supporting the idea that we must give Al Gore and his carbon mafia all our money and submit to global government, but in between the lines we can piece together a story of successive civilizations which were destroyed by drought. The causes of these droughts are largely left unexplored by mainstream journalists, with speculation confined to statements like “The findings also suggest that modern-day civilizations may be vulnerable to climate change”
There isn’t much evidence that the Sumerians had cars, or package holidays, or air conditioning, so it’s unlikely that their plights had much to do with anything that would easily be construed as supporting carbon taxes and state interference in every aspect of our lives, so the reasons for the climate change are pretty much left out of the reports we get to see in the mainstream media. However, it doesn’t take a genius to work out that agriculture (and thus deforestation) might at least have something to do with it.
More in the article, at Livescience.com, (and many other outlets too) but it doesn’t go into causes much.
Music: Excerpt from Way to the Roots by Haytham Safia Quartet
Thanks to Miguel Jaramillo for all the great desert photos.
Extreme tree: http://www.flickr.com/photos/pedronet/3975329408/sizes/l/in/photostream/
Cat: http://www.scenicreflections.com/download/282058/running_cat_Wallpaper/ (watch out, loads of popups etc…)
(2005) Australian scientists say they have found proof that cutting down forests reduces rainfall. The finding, independent of previous anecdotal evidence and computer modelling, uses physics and chemistry to show how the climate changes when forests are lost, by analyzing variations in the molecular structure of rain along the Amazon River.
Not all water, Professor Henderson-Sellers said, was made from the recipe of two atoms of “common” hydrogen and one of “regular” oxygen. About one in every 500 water molecules had its second hydrogen atom replaced by a heavier version called deuterium. And one in every 6500 molecules included a heavy version of the oxygen atom.
Knowing the ratio allowed scientists to trace the Amazon’s water as it flowed into the Atlantic, evaporated, blew back inland with the trade winds to fall again as rain, and finally returned to the river. The study showed that since the 1970s the ratio of the heavy molecules found in rain over the Amazon and the Andes had declined significantly. The only possible explanation was that they were no longer being returned to the atmosphere to fall again as rain because the vegetation was disappearing. “With many trees now gone and the forest degraded, the moisture that reaches the Andes has clearly lost the heavy isotopes that used to be recycled so effectively,” Professor Henderson-Sellers said.
“This is the first demonstration that deforestation has an observable impact on rainfall.”
Castles, field systems, cemeteries and irrigation don’t sound like the things you would find in a desert, yet archaeologists exploring the ruins of the Garamantes civilization estimate that it was in existence as recently as 5 to 500 A.D. In one of the most inhospitable parts of the Sahara, there were farms as recently as Roman times!
If, as is commonly posited by those who haven’t thought about it much, the Sahara is a desert due to purely ‘natural’ reasons, then there may be nothing we can do about it. But evidence abounds that human activity (primarily unintelligent farming methods) was the real cause, and this discovery adds support to that view.
More at fox news, where they predictably used it to slag off Gadhafi.
Isotope studies have shown that almost all oceanic moisture falls as rain within the first 150 miles from any coast. All the rest of the rainfall on land is recycled water, evaporated from the land and the vegetation on it. Bare land such as sand or rock desert can only evaporate a small amount of the water before it runs off back to the sea. Farmland will hold a little, but the best reservoir is a forest.
A single oak tree may have ten to thirty acres of leaf surface, so forests are the best thing for ensuring that inland areas get rain. In fact, to destroy the Amazon forest, all we need to do is to chop down the first 200 miles, and we’re busy doing that now.
Until relatively recently, most scientists thought rain was caused by mineral particles in the air which were just the right size for water (or ice) to condense around them. Research is beginning to show that a major factor in rain creation could be bacteria associated with plants. http://en.wikipedia.org/wiki/Bioprecipitation
If this is true then it is yet another way in which forests create rain. A forest has a far greater plant surface area than farmland or desert.
The image shows two views of the rabbit-proof fence, stretching aobut 2,000 miles across South-Western Australia. It separates off native land from farmland with the idea of keeping rabbits out.
Clouds form a lot more on the native side than the other, showing a correlation between farmland and decreased rainfall. That’s it really, but there are some speculations and other stuff in a NY Times article about it.
There is a research paper by Tom Lyons of Murdoch University, impact_of_clearing (pdf) which goes into detail, and an abstract of another paper: The role of land use change on the development and evolution of the west coast trough, convective clouds, and precipitation in southwest Australia on the JGR site
(And the fence, it doesn’t work, obviously — what kind of idiot would try to build a 2,000 mile long version of something they haven’t invented a one mile version of yet? And more to the point, what kind of idiot would pay them to do it? Oh, hang on, the kind of idiot that would chop all the trees down and expect to just keep on farming without them forever. The fence builders saw them coming didn’t they?!