Flying Rivers
October 19, 2022 3:55 PM   Subscribe

The biotic pump theory proposes that evaporation or transpiration causes clouds formation that reduces atmospheric pressure, and then draws additional moist air into the regions with high evapotranspiration, i.e. forests draw moist air inland, while deserts lose moisture to seas. Although unproven, rainfall patterns fit the theory. posted by jeffburdges (11 comments total) 22 users marked this as a favorite
 
I read about the atmospheric river in a book about soil health (maybe in The Soil Will Save Us) and how a project in the Amazon was showing some of the biotic pump effects? I wish my goldfish brain actually could recollect the book itself.

Thanks for posting!
posted by spamandkimchi at 4:43 PM on October 19, 2022 [1 favorite]


So wait.. Rain doesn't follow the plow?
posted by Nerd of the North at 4:46 PM on October 19, 2022 [6 favorites]


“Forests precede civilizations and deserts follow them.”
— François-René de Chateaubriand
posted by jeffburdges at 4:46 PM on October 19, 2022 [9 favorites]


I did a quick search on Google Books and found it! It's a book about water, not soil. Water in Plain Sight: Hope for a Thirsty World by Judith Schwartz.
posted by spamandkimchi at 4:47 PM on October 19, 2022 [3 favorites]


Great post! We really know so little about how our planet works eh! Just this morning I sent some info to a friend about the (recently discovered) oddity where soil holds water at different ages (as isotope variants) based on how the water arrived – rain from the sea, rain from the land, as snow etc, & how old it is). Oh, I see it's covered a little in the unproven link above.

This results in counterintuitive effects such as flood water not always being the stuff that is falling from the sky now! Most accessible look at that Whither field hydrology? The need for discovery science and outrageous hydrological hypotheses [wiley pdf goto page 7]

Meanwhile stormwater engineers (@ least in NZ) seldom even accept plant transpiration.
posted by unearthed at 7:54 PM on October 19, 2022 [2 favorites]


Ascension Island in the South Atlantic is one counter to jeffburdgesForests precede civilizations and deserts follow them.”
Occupied by the British Navy in 1815 with a watching brief on Napoleon in St Helena [nearest land albeit 1300 km away], the island was visited in 1836 by Charles Darwin and HMS Beagle towards the end of their epic voyage round the world, the Helenots joked "We know we live on a rock, but the poor people of Ascension live on a cinder", so he was partly prepared for the bleak, arid, windswept and unwelcoming lava-fields which he encountered. The lack of water was so severe that Ascension was victualled like a ship at sea and was, indeed, named HMS Ascension.

Darwin thought that the water supply might be augmented if the volcanic peaks could have a more or less permanent cloudy crown such as he'd seen on numerous tropical islands in the Pacific. One difference between Ascension and, say, Tahiti was that the latter had a rain-forest. Maybe if you built a forest, rain would come? Darwin was not the first man to voice such an idea but he was remarkably well connected to the scientific-political establishment. When he returned to England he shared this idea and his enthusiasm for it with his pal Joseph Hooker, whose father was director of the botanic garden in Kew. Hooker made his own 'site-visit' to Ascension in 1843 on his way back from a famous Antarctic exploration and could only identify a single species that passed as a tree. At the behest of the Admiralty, Hooker undertook to ship a variety to trees, shrubs and understory plants to Ascension to a) encourage aforestation to promote clouds and rainfall b) to stablise steep inclines and slow run-off c) try out a few xerophytes that would tolerate the prevailing salt-arid conditions and finally d) provide some fresh food for the garrison. Everything had to be proof against goats, rats and mice which had been introduced since the island was discovered in 1502. The species sent out were chosen using the best scientific information that could be obtained. Survival was a bit of a lottery: some seeds and saplings got the mildew aboard ship; others were eaten by the goats and some wouldn't have made it anyway for various unfathomable genetic or ecological imperatives. In all of this, nobody paid the slightest heed to the existence or well-being of the microbial flora surrounding the roots of the imports.

It was a striking success. 20 years later there were thickets of trees comprising dozens of different species all propping each other up in a part-artificial, part-natural reduced-instruction-set ecosystem. Heck, the highest point on the island is now called Green Mountain. The diversity of the vegetation increased but the endemic species have been hard hit by the invasives and not just the goats. Of the ten native species of ferns known in 1850, three are now extinct. Interestingly, the greening of Ascension seems to be concentrated in the higher regions, down on the flattish volcanic plain the landscape can still look unrelentingly bleak. The local tourist office, for example boasts the "worst golf course in the World": where the greens are browns.
posted by BobTheScientist at 12:27 AM on October 20, 2022 [9 favorites]


Pine trees can draw moisture from fog and mist due to electrostatic effects of their pointy needles. It’s possible they can thrive without drawing any additional rain. One foggy morning here recently there was a street-side pine where the ground was wet under the tree but not around it.
posted by sjswitzer at 2:16 PM on October 20, 2022 [3 favorites]


Ascension Island seemingly supports this biotic pump theory. It's clear Chateaubriand's quote should be read statistically: All empires created gardens, while doing their degradation elsewhere.

All this fits under the maximum power principle, which like the 2nd law of thermodynamics only speaks above the full system, not about local behavior.

We can disobey the maximum power principle for a while, unlike the 2nd law, but once we disobey genetic or memetic selection turns against us. Rafael Trujillo supposedly kept the Dominican Republic green, while Hati wrecked itself.

In fact, island bound animals adapt to be less fecund, consume less, etc., so external forces like constraints or conflicts actually change the whole dynamic behind the maximum power principle. We've this problem that nation A never threatens nation B to stop B cutting down forests to protect the rainfall in A, but maybe this changes.
posted by jeffburdges at 2:44 PM on October 20, 2022






“Les forêts précèdent les peuples, les déserts les suivent.”
— François René de Chateaubriand
posted by jeffburdges at 3:40 PM on November 18, 2022 [1 favorite]


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