In this feature of the Red Sun Rises, we are going to explore the great debate of a seemingly obscure subject. For much of western history little or no thought was given to why one area of our planet is a desert and another a forest, it was simply God’s will. Since the scientific revolution and the 1700’s, theories have pointed to the wobble of the earth, fluctuations in the sun, and different latitudes and meteorological mechanisms. One idea was never questioned until recently, Forests exist because enough rain falls in an area to support them. However, modern science is overturning that notion, called the “biotic pump theory” it seeks to explain that it is the Forests itself which create the rain and wind that brings oceanic and biogenic moisture inland. This modern theory explores the too often ignored interplay between climate and biology. In todays feature we will explore this fundamental question and see which theories hold up under the scrutiny of environmental history. If it turns out the biotic pump theory is a true contender, which I believe to be the case, then the implications are absolutely world shattering.
In grade school or if you simply google “why does Earth have deserts” you are treated to this above, the Hadley cell model of atmospheric circulation. You have the warm thermals of the equator rising, condensing and precipitating, and then as the moisture is “squeegeed” out by the cool upper atmosphere, then we have drier air falling back down to the surface at around 30 degree latitude. This toy model of atmospheric circulation is so simple you could explain it to a grade schooler, and many teachers around the country do. But like most models they aren’t a full picture of reality, because reality is always more complex than you expect it to be. So there we have it, deserts form around 30 degrees latitude both south and north. The only problem is if you take this at face value and look at satellite imagery for more than 30 seconds you can point out a dozen different examples of places that should be deserts that aren’t and places that should be forest but are deserts. So if Intertropical Convergence Zones and Hadley cells are useful models that don’t explain the full picture here, what might we be missing?
In the 20th century science was building upon 1800’s ideas rooted in the traditional Christian values of Western Europe and the scientific revolution, which leads to a very strong anthropocentric bias. Trees, Forests, Plants, and animals were only put on this earth only as resources for the dominion of Man. The idea that the other 99.9999% of species on earth may play key roles in regulating climate, habitat and the ability for humans to live on this planet, was not quite in the realm of imagination yet.
Enter the 21st century: The Biotic Pump
The biotic pump was pioneered by two scientist from the St. Petersburg Nuclear Physics Institute, Anastassia Makarieva and Victor Gorshkov in 2007. They had been asking themselves a serious chicken and the egg problem. Which came first, rain or forests? Did forests exist only where rainfall made it possible, or did the forests themselves “summon” the rain? It was in this paper they detailed the physical mechanisms of how forests summon the rain. Forests and plant cover in general with all it’s leaves have lots of surface area compared to barren land, which means more space for water to condense. When water condenses it creates lower air pressure, which creates an inland wind drawing in more moisture. Plants all “breath” water vapor through evapo-transpiration, restoring more moisture to the atmosphere, which condenses on more forests deeper into the land, creating an atmospheric pipeline of moisture (see below).
The biotic pump accurately explains continental wind and rainfall patterns. Even while the most advanced global circulation models in meteorology cannot reproduce the Amazon basin water cycle. These global models underestimate the amount of moisture brought by wind into the Amazon basin by over 200%. Clearly advances in meteorological models need to take into account these newly discovered feedback loops and physical mechanisms.
In the winter months of temperate climates you can even see how the forests can effect where rain falls. As leaves develop on trees in the spring and summer, they help bring the moisture and rainfall inland. In the fall and winter when the trees go dormant, the rainfall is concentrated off the coast because the forests are no longer actively bringing the moisture inland.
For some more common questions about the biotic pump look here and here.
So humor me for a moment, assume that forests are the primary drivers of rainfall and prevailing wind patterns on this planet. What are the implications? Life on earth and human civilizations require water for their survival. If we cut down or break up large area of continuous native forests via thirst for timber or land development space, what happens? In theory we would reduce the rainfall of that area. An area would lose its root structure from forests, which stabilizes the soil leading to an intensifying feedback loop of mudslides, erosion, then drought and aridification. Eventually the end result is a degraded wasteland of low diversity desert. Of course if this is true, then would we have seen it already? Well boy, do I have some examples for you.
Sao Paulo is a Coastal city in Southern Brazil. In the past decade the city of over 12 million people has experienced serious water issues. This past summer residents of the city were forced to grab buckets of water from swimming pools to flush their toilets. Starbucks only offered coke and beer because there was no water for coffee. This is a city tinkering on the abyss. Sao Paolo is also a major hub for southern Brazilian agricultural exports which keeps soybean, meat and other food prices low for people around the world. So entertaining this theory about deforestation and rainfall, what was the situation in Southern Brazil?
It seems they extensively deforested the region, and are now experiencing much less rainfall.
This is just one of many modern examples of deforestation having serious state destroying side effects.
But wait…… There’s more!!!!!!!
We are traveling across the Atlantic Ocean from Sao Paulo in Brazil to Nigeria on the West Coast of Africa. Nigeria is at approximately the same latitude as Coast Rica, a Central American country known for its beautiful Rainforest. Nigeria however, has shared a very different fate at the influence of colonial powers and in the modern day a no-holds barred scramble for unrestricted economic growth. Nigeria since the 1800’s has lost over 90% of its rainforest. Nigeria stands today as one of the most deforested countries on planet earth. According to climate observations rainfall has been decreasing incrementally since the 1960’s.
The increasing periods of drought and flooding, erosion and desertification is driving a whole host of chaos in Nigeria. The trend we are seeing in Nigeria is the rainfall is failing to show up more and more often the farther from the coast we get. Northern Nigeria is bearing the worst of the chaos.
As the rain fails, grasslands are turning to cracked dry earth making nomadic herdsmen desperate to find green land for their cattle. At the same time these herdsmen are raiding poor farmers ruining their crops for the entire year, which is a death spiral of conflict and collapse. I want you to imagine the smell of gunpowder, hear the screams, the distinct sound of rifles chattering as tribal groups fight for control of dwindling habitat. I want you to imagine the disturbing silence of the desert that follows after, the cool breeze of the night, no songs of birds, no laughing of people, no rustling of trees, just nothing but lone and level sands stretching into the distance.
But if Deforestation can lead to decreased rainfall, erosion, and start the feedback loops to desertification. Can the process be reversed? The answer is complicated. Yes it can, however it has to be done right. Restoring native high biodiversity forests and ecosystems can rejuvenate water retention, but only by linking long tracts of forest from the coast to the intercontinental areas can the biotic pump be restored. Most of the failings of modern reforestation projects use a monoculture of trees making them vulnerable to disease and the same types of stressors. There are no projects that I know of that incorporate the biotic pump into their restoration planning attempting to link the coastal forest to the inland forest. If countries thought of their native forest as strategic infrastructure assets with the same importance as an oil pipeline, they may not be so willing indulge in the slow suicide most have civilizations stumbled towards. In fact, we can think of forests as fresh water pipelines, except they bring that water through the sky and not a metal tube. However, if we cut that pipeline/forests into little pieces or break it up to much, it “leaks” and the water stops reaching the continental interior.
We have discussed two great examples from the modern era of deforestation causing decreased rainfall and jumpstarting desertification. But is this something that has been happening much longer than the modern area? Are old deserts of earth actually the graveyards of old and ancient civilizations? With an understanding of the Biotic pump mechanism, how can we rule out whether these old deserts are not from the same processes played out over longer time scales by ancient peoples? One thing we have to keep in mind going forward is that the farther back in time we go the harder it is to tease out the correlation between human activities, deforestation and rain. Lets head over to the Scottish Highlands.
This is what most of the Scottish Highlands look like today, barren semi grassy rocky terrain with exceptionally low biodiversity. Would you believe this area used to be a rich biodiverse rainforest, similar to the rainforest of the pacific northwest? 6000 years ago, the arrival of agriculturalist heralded the beginning of the end for the Caledonian Rainforest. Cutting down timber to cook food, build dwellings, create charcoal for metallurgy and construct ships took its toll on this ancient forest. By the time the Romans arrived whos accounts of the area spoke of vast and dense forests, the forests had already been reduced by human activity by over 50%.
Ecosystems changes such as the persistent grazing by sheep kept the forests from ever regenerating, leading to the monoculture of hardy grasses and shrubs found in other areas of the world where forests were cut down and grazing sheep kept them from ever recovering.
The Scottish landscape has a very similar feel to another landscape at a completely different latitude. If we head down to Greece and it’s Mediterranean climate we find some eerily similar rocky hillsides.
So we have a question of where did all these forests go? If Greece wasn’t always mostly rocky barren hillsides, where did all those trees go?
Greek Triremes were up to 120 ft long with over 170 oars for just one ship. At the Battle of Salamis where the Greek city states battled the Persian Empire of Xerces the First, over 1200 ships were involved in one of the most massive naval battles of the ancient western world. Each Trireme weighed over 50 tons all made of specific types of lumber. These were were just military ships, who knows how many trade and supply ships were built off the ancient forests of Greek highlands. This doesn’t even include the wood cost in cooking meals for crew and the metallurgy refined for armaments. While ancient empires weren’t harvesting lumber and wood as fast as modern nations, they certainly had way more time to do it. While Greece isn’t a desert today, much of the land is degraded, rocky and barren after use and abuse by thousands of years of human habitation.
I think we have established a little bit of a pattern between civilizations, deforestation and the creation of arid degraded land. Given what we know now about the biotic pump, deforestation and rainfall, I want to rethink this picture of the middle east you may have seen a few times.
Behold the Middle East, the Cradle of civilization. In one picture you have almost 10,000 years of ancient civilizations disappearing into the sands. Now was this area always full of such barren desert explained by the latitude. Can we rule out that these civilizations over thousands of years didn’t degrade ancient forests, break their biotic pumps, and turning their once lush and thriving lands into bone dry graveyards? I want to show you a series of “interesting coincidences.” The first takes us to a curiosity of Hippos in deserts. Hippos spend most of their life underwater in lakes and rivers munching on different aquatic plants.
So how do we explain this picture below? Ancient Petroglyph drawings of hippos, giraffes and crocodiles in the desert? Do you think its more likely that this area was lush and green at one time, or that someone decided to make a journey out into a desert just to draw on rocks, pictures of animals that didn’t and couldn’t live there?
Did you know Ancient Egyptians were some of the first known Arborculturalist
(tree farmers)? In the 11th century approximately 1000 years ago, the Ancient Egyptians had a whole system of forest management. Now why would a country that is almost completely desert need a forest management system, are we perhaps underestimating the amount of ancient forest civilizations have felled over thousands of years?
We know from a combination of archeological records, palynology(study of ancient pollen), and geology that the worlds largest desert the Sahara, used to be very wet and green. This wet Sahara period lasted from 14,500 years ago to as little as 5,000 years ago. Many theories are thrown at the wall to explain this climactic shift, everything from orbital wobbles to changes in the Intertropical convergence zone. To date, I am not sure many people have examined this in light of our understanding of the unique role vegetation plays in augmenting the local rainfall. It is yet another interesting coincidence that this Wet Sahara ended precisely around the time, major civilizations started to develop in this area?
Ancient Egypt became the major power of North Africa and one of the worlds first known civilizations around 3100 BC, which is around 5100 Years ago. What a remarkable coincidence that the Sahara began drying out around the same time a major civilization developed. Let me reword this for you, Ancient Egypt developed BECAUSE it started exploiting the forests of North Africa for power and wealth, which led to the development of the dry relatively inhospitable Sahara we know today. Almost every where we find a desert, we can find a major civilization that appears around the same time. Lets look into an area that hits a little closer to home.
Could some of the major desert areas of the “New World” have been inadvertently created by human activity? Up until 2021, Archeologist had assumed that no humans existed in North America up until 13,500 years ago when Siberian hunters followed herds across the Bering land bridge that formed during the last ice age. Well, Human history is full of inconvenient coincidences… These below are human footprints found in White Sands, New Mexico and dated to at least 23,000 years ago. How many human civilizations could have developed in the New World during that time, leaving deserts as footprints along the landscape. We simply don’t know, but these are an awful lot of coincidences.
Now if deforesting an area can remove rainfall from land, can reforesting an area bring the water back? We will answer that question along with studying the curious case of a civilization that never collapsed, in our next installment of The Red Sun Rises: Hope on the Horizon.