Bio-Rain Corridor

How to restore the rain

A biological corridor is a connected area of habitat along which wildlife can roam, where elk can travel between the lowlands in the winter to the higher ranges in the summer, where butterflies can navigate across the landscape to pollinate different plants, and where wolves can find access to habitat and food. Its an evocative term as it both summarizes succinctly an ecological restoration pattern and gives a sense of why its important to wildlife.

Water practitioners and hydro-climatologists have delineated how we can eco-restore the land to bring back the rain, by revegetating the land from ocean to inland. I would like to propose a term for this connected area - the ‘bio-rain corridor’. This term helps describe the continental behavior of rain, it accentuates the importance that biology has on rain patterns, and it connotes eco-restoration possibilities by its similarity to the term biological corridor.

Hubert Savenije, a Dutch hydrologist studied moisture hopping ( aka the small water cycle) in the Sahel in Africa. Moisture hopping is where water vapor blows inland, falls as rain to the ground, and then is evapotranspired to blow further inland. Savenije found that a lot of the rainfall further inland had come from the coastal forests, and that as these forests had been chopped down, the rainfall decreased. [1]

Savenije’s student, Ruud van der Ent, modeled the flow of continental water moisture, and found that in South America the water moisture hopped from the North Atlantic ocean into the Amazon rainforests, then was turned southward by the Andes mountain, to hop into southeastern South America. 70% of the water above the Amazon forests ended up in southeastern South America. [2]

[ diagram from Science magazine ]

Van der Ent found that 80% of the rain in China had moisture hopped across the boreal forests of Scandinavia and Russia.

[diagram shows how much water comes from ocean and how much from evapotranspiration globally]

Victor Gorshov and Anastasia Makarieva, two Russian atmospheric physicists have looked at the pattern of rainfall on continents. When there are not a continuous corridor of forests the rainfall decreases exponentially as one moves inland (see the D,E,F,G,H arrows in diagram below). When there are forests as in the Amazon in South America, the Congo rainforests in Africa, and the boreal forests of Russia, the rainfall does not decrease as one moves inland, it in fact increases slightly (see the arrows A,B,C in diagram below)

[ diagram from ref 3]

The forests and vegetation are creating a pathway for the rain to moisture hop inland via the small water cycle. The land is able to absorb the rainfall so that it can evapotranspire back up, to then blow further inland to create more rain. Vegetation also releases bacteria and fungi spores which float up into the air and help the water vapor nucleate into cloud droplets. The forests slow the wind down so that the water vapor has more chance to condense into rain. And the Biotic Pump hypothesis of Makarieva and Gorshov [4], theorizes that when the water vapor evapotranspired by forests condenses into clouds it creates a low pressure area that attracts more water vapor to blow in from the ocean.

In order to restore our rains further inland we need to restore the bio-rain corridor, a chain of vegetation that goes from the coast to further inland. Regreening our coastal cities, rewilding the area outside cities, restoring the various biomes can help decrease drought further inland. Depaving asphalt and concrete so that the earth can absorb rainfall aides the small water cycle.

Heres a map of how much we have deforested the world. Reforesting will help restore global rainfall patterns, will help guide our terrestial water cycles back into harmony.

The phrase “Slow it, sink it, spread it”, coined by Brock Dolman explains how we can work with the water cycle. I would like to suggest we can extend this to “Slow it, sink it, spread it, hop it, lift it” ( see previous article in this newsletter) . The ‘hop it’ would refer to the moisture hopping along the bio-rain corridor. And the ‘lift it’ would refer to how tree roots and mycelia lift ( the technical term is hydraulic lift) the groundwater into the soil above. That water can then evapotranspire and become part of the small water cycle. Hydroclimatologist Francina Dominguez’s research shows there is a groundwater-rain cycle (as discussed in a previous edition of this newsletter). When there is healthier soil and more vegetation the rain can be absorbed and sink down to increase groundwater, which then can be lifted up to create more moisture hopping.

Water begins from the ocean, and blows towards continents, alighting on forests, grasslands, savannahs, wetlands, travelling over mountains, slithering through organism carved pores in the soil, descending down into underground bedrock, squeezing through roots and hyphae, phase transitioning between vapor, liquid and sometimes ice, until it ends up further inland, hydrating the fauna and flora there. Water hops, sinks, and lifts along the bio-rain corridor.

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5 KEY WATER TALES

Nov 3rd Thu 9am-1030am (Pacific Time)

We are putting on an roundtable event to clarify what are the central narratives/tales of water, and to coordinate efforts to get these stories out to the public.

Here are some of the possible narratives to think about. What would be your top 5 water narratives/tales?

A. Evapotranspiration cools earth B. Small water cycle creates rain C. Hydraulic lift keeps soil wet D. Wetlands cleanse water E. Cities can recycle stormwater F. Organic soil absorbs more rainwater G. Slowing water keeps continents hydrated H. Tile drainage wastes water I. Wetlands humidify winds lessening wildfires J. Wetlands replenish groundwater K. Groundwater is our water bank L. Groundwater increases the small water cycle M. Groundwater quenches wildfires N. Forests attract rain O. Biodiversity increases small water cycle P. Drought-fire-flood cycle , aka Watershed death cycle (from Zach Weiss) Q. Absorb rainfall to lessen droughts, floods, fire, and heat R. Dams block fish, sediment, wetlands, and groundwater S. Plants regulate heat via water T. Animals changes soil which changes water cycle U. Ecological succession tends to increase small water cycle V. Healthy ecosystems creates clouds which can cool earth X. Increasing small water cycle lessens urban heat domes. Y. Increasing land evapotranspiration decreases hurricanes and extreme large rainfall. Z. Regenerative agriculture saves water Z2. How we relate to water affects the water cycle Z3. Beavers hydrate the landscape

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References:

[1] Savenije, Hubert HG. "New definitions for moisture recycling and the relationship with land-use changes in the Sahel." Journal of Hydrology 167, no. 1-4 (1995): 57-78 https://www.sciencedirect.com/science/article/abs/pii/002216949402632L

[2] van der Ent, R. J. and Savenije, H. H. G.: Length and time scales of atmospheric moisture recycling, Atmos. Chem. Phys., 11, 1853–1863, https://doi.org/10.5194/acp-11-1853-2011, 2011

[3] How Forests Attract Rain: An Examination of a New Hypothesis Sheil, Douglas et al. BioScience (2009),59(4): 341 https://doi.org/10.1525/bio.2009.59.4.12

[4] Makarieva, Anastassia M., and Victor G. Gorshkov. "Biotic pump of atmospheric moisture as driver of the hydrological cycle on land." Hydrology and earth system sciences 11, no. 2 (2007): 1013-1033. https://hess.copernicus.org/articles/11/1013/2007/

[5] Makarieva, Anastassia M., Victor G. Gorshkov, and Bai-Lian Li. "Precipitation on land versus distance from the ocean: evidence for a forest pump of atmospheric moisture." Ecological complexity 6, no. 3 (2009): 302-307. https://www.sciencedirect.com/science/article/abs/pii/S1476945X08000834