The Empty Sea -- An Ongoing Saga

 

"The Empty Sea," a Report to the Club of Rome by Ugo Bardi and Ilaria Perissi, was translated into Chinese and published in China at the end of September of this year. As a comment to this new version of the book, I am reproducing here, with the kind permission of the author, a post by Coty Perry that deals with the same basic problems that the book describes. How the marine ecosystem is being damaged by human activities. Will it survive? It is part of an ongoing saga that sees humans killing everything on this planet without realizing that, in doing that, eventually they will be killing themselves

For those of you who can't read Chinese, the English version of the book is available on Springer's site. A version in Italian is also available at this link. 

 

Overfishing, Conservation, Sustainability, and Farmed Fish

By Coty Perry, "Your Bass Guy" -- July 15, 2022

As with many other aspects of government policy, overfishing and other fishing-related environmental issues are a real problem, but it’s not clear that government intervention is the solution. Indeed, it might be one of the main drivers of overfishing and other conservation and sustainability issues stemming from commercial fishing. Much like drone fishing, there are serious ethical issues of interest to the average angler. 

There’s another commonality that overfishing has with environmental issues more broadly: The Western companies primarily concerned with serious efforts to curb overfishing are not the ones who are most guilty of overfishing. What this means is that the costs of overfishing are disproportionately borne by the countries least engaged in practices that are counter to efforts to make commercial fishing more sustainable while also promoting conservation of fish biodiversity. 

All of these are important issues not just for commercial fishermen, but also those interested in questions of conservation and sustainability in general, as well as recreational fisherman and basically anyone who uses fish as a food source. As the ocean goes, so goes the planet, so it is of paramount importance for everyone to educate themselves on what is driving overfishing, what its consequences are, and what meaningful steps — not simply theater to feel as if “something is being done” — can be taken.

Indeed, over three billion people around the world rely on fish as their primary source of protein. About 12 percent of the world relies on fisheries in some form or another. 90 percent of these being small-scale fishermen — “think a small crew in a boat, not a ship,” using small nets or even rods, reels and lures not too different from the kind you probably use.

There are 18.9 million fishermen in the world, with 90 percent of them falling under the same small-scale fisherman rubric discussed above. 

Overfishing Definition: What is Overfishing?

First, take heart: As a recreational fisherman you are almost certainly not guilty of “overfishing.” This is an issue for commercial fishermen in the fishing industry who are trawling the ocean depths with massive nets to catch enough fish to make a living for themselves and their families, not the angler who enjoys a little peace and quiet on the weekends. 

Overfishing is, in some sense, a rational reaction to increasing market needs for fish. Most people consume approximately twice as much fish as they did 50 years ago and there are four times as many people on earth as there were at the close of the 1960s. This is one driver of the 30 percent of commercially fished waters being classified as “overfished.” This means that the stock of available fishing waters are being depleted faster than they can be replaced.

There is a simple and straightforward definition of when an area is being “overfished” and it’s not simply about catching “too many” fish. Overfishing occurs when the breeding stock of an area becomes so depleted that the fish in the area cannot replenish themselves. 

At best, this means fewer fish next year than there are this year. At worst, it means that a species of fish cannot be fished out of a specific area anymore. This also goes hand-in-hand with wasteful forms of fishing that harvest not just the fish the trawler is looking for, but just about every other organism big enough to be caught in a net. Over 80 percent of fish are caught in these kinds of nets but fish aren’t the only things caught in nets.

What’s more, there are a number of wide-reaching consequences of overfishing. It’s not simply bad because it depletes the fish stocks of available resources, though that certainly is one reason why it’s bad. Others include:

• Increased Algae in the Water: Like many other things, algae is great but too much of it is very bad. When there are fewer fish in the water, algae doesn’t get eaten. This increases the acidity in the world’s oceans, which negatively impacts not only the remaining fish, but also the reefs and plankton.

• Destruction of Fishing Communities: Overfishing can completely destroy fish populations and communities that once relied upon the fish that were there. This is particularly true for island communities. And it’s worth remembering that there are many isolated points on the globe where fishing isn’t just the driver of the economy, but also the primary source of protein for the population. When either or both of these disappear, the community disappears along with it.

• Tougher Fishing for Small Vessels: If you’re a fan of small business, you ought to be concerned about overfishing. That’s because overfishing is mostly done by large vessels and makes it harder for smaller ones to meet their quotas. With over 40 million people around the world getting their food and livelihood from fishing, this is a serious problem.

• Ghost Fishing: Ghost fishing refers to abandoned man-made fishing gear that is left behind. It’s believed that an estimated 25,000 nets float throughout the Northeast Atlantic. This left behind gear becomes a death trap for all marine life that swim through that area. While much of this is caused due to storms and natural disasters, much of it is the result of ignorance and neglect on behalf of commercial fishermen.

• Species Pushed to Near Extinction: When we hear that a fish species is being depleted, we often think it’s fine because they can be found somewhere else. However, many species of fish are being pushed close to extinction by overfishing, such as several species of cod, tuna, halibut and even lobster.

• Bycatch: If you’re old enough to remember people being concerned about dolphins caught in tuna nets, you know what bycatch is: It’s when marine life that is not being sought by commercial fishermen is caught in their nets as a byproduct. The possibility of bycatch increases dramatically with overfishing.

• Waste: Overfishing creates waste in the supply chain. Approximately 20 percent of all fish in the United States is lost in the supply chain due to overfishing. In the Third World this rises to 30 percent thanks to a lack of available freezing devices. What this means is that even though there are more fish being caught than ever, there is also massive waste of harvested fish.

• Mystery Fish: Because of overfishing, there are a significant amount of fish at your local fish market and on the shelves of your local grocery store that aren’t what they are labelled as. Just because something says that it’s cod doesn’t mean that it actually is. To give you an idea of the scope of this problem, only 13 percent of the “red snapper” on the market is actually red snapper. Most of this is unintentional due to the scale of fishing done today, but much of it is not, hiding behind the unfortunate realities of mass scale fishing to pass off inferior products to unwitting customers. 

So why is overfishing happening? There are a variety of factors driving overfishing that we will delve into here, the bird’s eye view is below.

• Regulation: Regulations are incredibly difficult to enforce even when they are carefully crafted, which they often are not. The worst offenders have little regulations in place and none of these regulations apply in international waters, which are effectively a Wild West.

• Unreported Fishing: Existing regulations force many fisherman to do their fishing “off the books” if they wish to turn a profit. This is especially true in developing nations.

• Mobile Processing: Mobile processing is when fish are processed before even returning to port. They are canned while still out at sea. Canned fish is increasingly taking up the fish consumption market at the expense of fresh fish.

• Subsidies: Anyone familiar with farm subsidies knows that these are actually bad for the production of healthy food. Subsidies for fishing are similar. They don’t generally go to small fisherman whom one would think are most in need, but rather to massive vessels doing fuel-intensive shipping. 

What’s more, subsidies encourage overfishing because the money keeps flowing no matter what — the more fish you catch, the more money you get, with no caps influenced by environmental impact fishing regulation. 

Indeed, according to the World Wildlife Fund, subsidies drive illegal fishing, which is closely tied with piracy, slavery and human trafficking. The University of British Columbia conducted a study that found that $22 billion (63 percent of all fishing subsidies) went toward subsidies that encourage overfishing. 

Of these, the main driver of overfishing is, predictably, government subsidies. So it is worth taking a few minutes to separate that out from the rest of these issues and give it some special attention. 

More on Overfishing and Government Subsidies

The subsidies that drive overfishing are highly lucrative: The governments of the world are giving away over $35 billion every year to fishermen. That’s about 20 percent of the value of all the commercially caught fish in the world every year. Subsidies are often directed at reducing the costs for megafishing companies — things like paying for their massive fuel budgets, the gear they need to catch fish, or even the vessels themselves. 

This effectively allows for large commercial fishing operations to take over the market or recapitalize at rates significantly below that of the market, disproportionately favoring them over their smaller competitors. 

It is this advantage that drives large mega fishing companies into unsustainable fishing practices. The end result of this is not just depleted stocks, but also lower yields due to long-term overfishing, as well as lowered costs of fish at market, which has some advantages for the consumer, but also makes it significantly harder for smaller operations to turn a profit. 

Such government subsidies could provide assistance to smaller fishermen, but are generally structured in a way that favors consolidation of the market and efforts counterproductive to conservation efforts. 

What Role Do Farmed Fish Play?

Farmed fish is a phenomenon that we take for granted today, but is actually a revolutionary method of bringing fish out of the water and onto our dinner tables. Originally, it was seen as a way of preserving the population of wild fish. The thinking was this: We could eat fish from fish farming while the wild stock replenished itself. 

At the same time, communities impacted by overfishing would find new ways to get income in an increasingly difficult market. Third world countries would have their protein needs met in a manner that did not negatively impact the environment. It was considered a big, easy win for the entire world. 

The reality, as is often the case, turned out to be a little different. Crowding thousands of fish together in small areas away from their natural habitat turns out to have a number of detrimental effects. Waste products, primarily fish poop, excess food and dead fish, begin to contaminate the areas around fish farms. What’s more, like other factory farms, fish farms require lots of pesticides and drugs thanks to the high concentrations of fish and the parasites and diseases that spread in these kinds of areas. 

Predictably, the chemicals used in making farmed fish possible are not contained in the areas where they are initially used. They spread into the surrounding waters and then simply become part of the water of the world, building up over time. In many cases, farmed fish are farmed in areas that are already heavily polluted. This is where the admonition to avoid eating too much fish for fear of contaminants like mercury has come from.

What’s more, the fish that we eat are not the only fish that are living at the fisheries. Often times, the preferred fish of the human consumer are carnivores that must eat lots of other fish to get up to an appropriate size to be part of the market. These fish, known as “reduction fish” or “trash fish” require the same kind of treatment that the larger fish they feed do. 

All told, it takes 26 pounds of feed to produce a single pound of tuna, making farmed fishing an incredibly inefficient way of bringing food to market. Indeed, 37 percent of all seafood globally is now fed for farmed fish, up dramatically from 7.7 percent in 1948. 

Perhaps worst of all, farmed fish simply do not have the same nutritional value as their wild counterparts, losing almost all of the Omega-3 fatty acids that make fish such a prized part of the modern diet. 

Salmon, for example, is only healthy when it is caught in the wild. Farmed salmon is essentially a form of junk food. This is in large part due to the diet that the fish eat in fish farms, which is high in fat and uses soy as a primary source of protein. Toxins at the farms concentrate in the fatty tissue of the salmon. Concentrations of the harmful chemical PCB are found in concentrations eight times higher in farmed fish than traditionally caught wild salmon.

 

The pesticides, of course, are not used for no reason, but because of the proliferation of pests due to the high concentrations of fish in the fisheries. Sea lice are one example of such pests, which can eat a live salmon down to the bone. 

These pests do not stay in the fisheries, but quickly spread to the surrounding waters and infect wild salmon as well as their farmed counterparts. The pests aren’t the only ones escaping: Farmed fish often escape from their habitats and compete with the native fish for resources, becoming an invasive species. 

Subsidies vary from one country to another and specific statistics about how much goes to fish farms is generally not forthcoming. But fish farms effectively move the problem of overfishing from the wild oceans and into more enclosed areas. This does not solve any of the problems of overfishing. It merely creates new ones with no less impact on the environment. 

Which Countries Are Overfishing?

As stated above, the main offenders with regard to overfishing tend to not be developed Western countries, but countries from the undeveloped world and parts of Asia. Sadly, the United States is the only Western nation that appeared on a “shame list” put out by Pew Charitable Trusts. This is known as the Pacific Six. The other members include Japan, Taiwan, China, South Korea and Indonesia. 

The list only refers to overfishing with regard to bluefin tuna, but it provides a snapshot of the face of overfishing internationally. Overfishing facts say that these six countries are fishing 80 percent of the world’s bluefin tuna. These countries took collectively 111,482 metric tons of bluefin tuna out of the waters in 2011 alone. 

However, when it comes to harmful subsidies there is a clear leader: China. A University of British Columbia study found that China provided more in the way of harmful subsidies encouraging overfishing than any other country on earth — $7.2 billion in 2018 or 21 percent of all global support. What’s more, subsidies that are more beneficial than harmful dropped by 73 percent.

The negative effects of overfishing are not taking place far away and in very abstract ways. They are causing communities right here in the United States to collapse. In the early 1990s, overfishing of cod caused entire communities in New England to collapse. Once this happens, it is very difficult to reverse. The effects are felt by the marine ecosystem but also by the people whose livelihoods depend on fishing. 

Another example of economic instability is the Japanese fish market. Japanese fishermen are able to catch far less fish than they used to, meaning that the Japanese are now eating more imported fish, often from the United States, than ever before. This creates a perverse situation where America exports most of its best salmon to other countries, but consumes some of the worst farmed salmon in the world today. 

Just How Bad Is Overfishing?

Surely overfishing can’t be that bad, right? The seas are just filled with tons of fish and it would take us forever to overfish to the point that they began to disappear entirely, right?

Think again. Overfishing is happening at biologically unsustainable levels. Pacific bluefin tuna, the type of fish discussed in the section above, has seen a 97 percent decline in overall population. This is important because the Pacific bluefin tuna is one of the most important predators in the ocean food chain. If it goes extinct the entire aquaculture will be irreparably disturbed. 

The first fish that disappear from an ecosystem are larger fish with a longer lifespan and reach reproductive age later in life. These are also the most desirable fish on the open market. When these fish disappear, the destructive fishing operations do not leave the area: They simply move down the food chain to less desirable catches like squid and sardines. This is called “fishing down the web” and it slowly destroys the entire ecosystem removing first the predator fish and then the prey. 

There are broader effects on the ecosystem beyond just the fish, effects that resonate throughout the entire Atlantic and Pacific ocean. Many of the smaller fish eat algae that grows on coral reefs. When these fish become overfished, the algae grows uncontrolled and the reefs suffer as a result. That deprives many marine life forms of their natural habitat, creating extreme disruption in the ocean ecosystem. 

What Are Some Alternatives to Government-Driven Overfishing?

While there are certainly policy solutions to rampant overfishing, not all solutions will come from governments. For example, there are emerging technological solutions that will make by catching and other forms of waste less prevalent and harmful. 

Simple innovations based on existing technologies, such as Fishtek Marine seek to save sea mammals from the nets of commercial fishermen while also increasing profit margins for these companies in a win-win scenario. Their device is small and inexpensive and thus does not present an undue burden to either the large-scale commercial fishing vessels or small fishermen looking to eke out a living in an increasingly difficult market. 

We must also recognize that current regulations simply do not work. In one extreme case, governments restricted fishing for certain forms of tuna for three days a year. This did absolutely nothing for the population of tuna, as the big commercial fishing companies simply employed methods to harvest as many fish in three days as they were previously getting in any entire year. 

This, in turn, led to a greater amount of bycatch and waste. Because the fishing operations didn’t have the luxury of time to ensure that they were only catching what they sought to catch, their truncated fishing season prized quantity over quality with predictable results. 

Quotas, specifically the “individual transferable quota” scheme used by New Zealand and many other countries does not seem to work as intended for a number of reasons. First, these quotas are, as the name might suggest, transferable. This means that little fishermen might consider it a better deal to simply sell their quota to a large commercial fishing operation rather than go to work for themselves and we’re back to square one. 

More generally speaking, quotas seem to be a source of waste. Here’s how they work: A fishing operation is given a specific tonnage of fish from a specific species that they can catch. However, not all fish are created equally. So when commercial fishing operations look at their catch and see that some of it is of higher quality than others, they discard the lower-quality fish in favor of higher-quality fish creating large amounts of waste. These discards can sometimes make up 40 percent of the catch. 

An alternative to the current system is one that balances the need for fish as a global protein source with a long-term view of the ecosystem, planning for having as many fish tomorrow as there are today and thus, a sustainable model for feeding the world and providing jobs. One way to do this would be to tie subsidies to conservation and sustainability efforts, rather than simply writing checks to large commercial fishing operations to build new boats and buy new equipment. Such a scheme would also prize smaller scale operations over larger ones. A more diversified source of the world’s fish would also be more resilient. 

One such alternative is called territorial use rights in fisheries management (TURF). In this case, individual fishermen or collectives of them are provided with long-term rights to fish in a specific area. This means that they have skin in the game. They don’t want to overfish the area because to do so would be to kill the goose that laid the golden egg. So they catch as many fish as is sustainable and no more. They have a vested, long-term interest in making sure that there is no overfishing in the fisheries that have been allotted to them. 

Not only does this make sustainable fishing more attractive, it also means that there is less government bureaucracy and red tape involved. Fishermen with TURF are allowed to catch as much as they like. It is assumed that sustainability is baked into the equation because the fishermen with rights want to preserve the fishing not just for the next year, but for the next generation and the one after that. This model has been used successfully by Chile, one of the most economically free countries in the world (more economically free, in fact, than the United States), to prevent overfishing and create sustainability. It is a market-driven model that prizes small producers with skin in the game over massive, transnational conglomerates with none. 

Belize, Denmark, and even the United States are other countries that have used TURF, with significantly positive results. While it’s nice to support the little guy over Big Fishing and we certainly support sustainability and conservation efforts, there’s another, perhaps more important and direct reason to support reforms designed to eliminate overfishing: food security. When bluefin tuna, for example, goes extinct, it’s not coming back. That means no more cans of tuna on the shelves of your local supermarket. 

That’s a big deal for people in developed, first-world countries, but a much bigger deal in developing countries. When major protein sources are depleted forever, there will be intensified competition for the resources that remain. This also creates unrest in the countries that are less able to compete in a global market due to issues of capital and scale. Even if you’re not concerned with overfishing, overfishing and the problems it creates will soon be on your doorstep unless corrective measures are taken before it’s too late.

Thinking like a Tree. Understanding the Role of Forests in the Ecosystem

The "Seneca Effect" blog deals a lot with collapses and you may find it a little catastrophistic. But I am also exploring other fields in a more positive mood. One is the concept of "holobiont," how living creatures organize themselves to form complex adaptive systems. Here is a post on this subject from my blog "The Proud Holobionts". 

The Greatest Holobiont on Earth: Old-Growth Forests

Reproduced from "The Proud Holobionts"

A "holobiont" is a living creature formed of independent, but cooperating, organisms. It is a wide-ranging concept that can explain many things not just about the ecosystem of our planet, but also about human society, and even more than that. Photo courtesy of Chuck Pezeshky. This post was modified and improved thanks to suggestions received from Anastassia Makarieva.

When was the last time that you walked through an old-growth forest? Do you remember the silence, the stillness of the air, the sensation of awe, the feeling that you are walking in a sacred place? The inside of a forest looks like a cathedral or, perhaps, it is the inside of a cathedral that is built in such a way to look like a forest, with columns as trees and vaults as the canopy.  If you don't have a forest or a cathedral nearby, you can get the same feeling by watching the masterful scene of the forest-God appearing in Miyazaki's movie, "Mononoke no Hime" (The Princess of the Ghosts). 

In a way, when you walk among trees, you feel that you are at home, the home that our remote ancestors left to embark on the mad adventure of becoming human. Yet, for some humans, trees have become enemies to be fought. And, as it is traditional in all wars, they are demonized and despised. It was the English landlord Jonah Barrington who commented about the destruction of Ireland's old forests that "trees are stumps provided by Nature for the repayment of debt." And, as it is traditional in all wars of extermination, not a single enemy was left standing. 

The war metaphor is engrained in our minds of primates, the only mammals that wage war against groups of their own species. So much that sometimes we imagine trees fighting back. In the "Trilogy of the Ring" by Tolkien, we see walking trees, the "ents," standing in arms against humanoid enemies and defeating them. Clearly, we feel guilty for what we have been doing to Earth's forests. A sensation of guilt that goes back to the time when the Sumerian King Gilgamesh and his friend Enkidu were cursed by the Goddess for having destroyed the sacred trees and killed their guardian, Humbaba. From that remote time, we have continued to destroy Earth's forests, and we are still doing that. 

Yet, if there is a war between trees and humans, it is not obvious that humans will win it. Trees are complex, structured, adaptable, tough, and resourceful creatures. Despite the human attempts to destroy them, they survive and even thrive. The most recent data indicate a greening trend of the whole planet [3], probably the result of humans pumping carbon dioxide (CO2) into the atmosphere (this greening is not necessarily a good thing, neither for trees nor for humans [4], [5]). 

But what are trees, exactly? They have no nervous system, no blood, no muscles, just as we have no capability of doing photosynthesis, nor of extracting minerals from the soil. Trees are truly alien creatures, yet they are made of the same building blocks as we are: their cells contain DNA and RNA molecules, their metabolism is based on the reduction of a molecule called adenosine triphosphate (ATP) created by mitochondria inside their cells, and much more. And, in a certain sense, trees do have a brain. The root system of a forest is a network similar to that of a human brain. It has been termed the “Wood-Wide Web” by Suzanne Simard and others [1]. What trees “think” is a difficult question for us, monkeys but, paraphrasing Sir. Thomas Browne [2], what trees are thinking, just like what song the Sirens sang to Ulysses, though puzzling questions are not beyond all conjecture. 

Whether trees think or not, they have the basic characteristics of all complex living systems: they are holobionts. "Holobiont" is a concept popularized by Lynn Margulis as the basic building block of the ecosphere. Holobionts are groups of creatures that collaborate with each other while maintaining their individual characteristics. If you are reading this text, you are probably a human being and, as such, you are also a holobiont. Your body hosts a wide variety of creatures, mostly bacteria, that help you in various tasks, for instance in digesting food. A forest is another kind of holobiont, vaster but also structured in terms of collaborating creatures. Trees could not exist alone, they need the all-important "mycorrhizal symbiosis." It has to do with the presence of fungi in the soil that collaborate with plant roots to create an entity called the “rhizosphere,” the holobiont that makes it possible for a forest to exist. Fungi process the minerals that exist in the soil and turn them into forms that plants can absorb. The plant, in turn, provides the fungi with energy in the form of sugars obtained from photosynthesis. 

So, even though trees are familiar creatures, it is surprising how many things are scarcely known about them and some are not known at all. So, let’s go through a few questions that disclose whole new worlds in front of us. 

First: wood. Everyone knows that trees are made of wood, of course, but why? Of course, its purpose is the mechanical support of the whole plant. But it is not a trivial question. If wood serves for mechanical support, why aren’t our bones made of wood? And why aren’t trees, instead, made of the stuff our bones are made of, mainly solid phosphate?

As usual, if something exists, there is some reason for it to exist. Within some limits, evolution may take different paths simply because it has started moving in a certain direction and it cannot move back. But, as things stand on Earth, wooden trunks are perfectly optimized for their purpose of support of a creature that doesn't move. Tree trunks (not palms, though) grow in concentric layers: it is well known that you can date a tree by counting the growth rings in its trunk. As a new layer grows, the inside layers die. They become just a support for the external layer called the “cambium” which is the living part of the trunk, containing the all-important “xylem”, the ducts that bring water and nutrients from the roots to the leaves. The cambium also contains the "phloem," another set of ducts that move water loaded with sugars in the opposite direction, toward the roots. The inner part of the trunk is dead, so it has no metabolic cost for the tree. Yet, it keeps providing the static support the tree needs. 

The disadvantage is that, because the internal part of the wood is dead, when a branch or a trunk is broken, it cannot be healed by reconnecting the two parts together. In animals, instead, the bones are alive: there is blood flowing through them. So, they can regrow and rebuild the damaged parts. It is probably a necessary feature for animals. They jump, run, fly, fall, roll, and do more acrobatic feats, often resulting in broken bones. Of course, a broken bone is a major danger, especially for a large animal. We don’t know exactly how many animals suffer broken bones and survive, but it seems that it is not uncommon: live bones are a crucial survival feature [6], [7]. But that's not so important for trees: they do not move and the main stress they face is a heavy gust of wind. But trees tend to protect themselves from wind by shouldering against each other – which is, by the way, another typical holobiont characteristic: trees help each other resisting wind, but not because they are ordered to do so by a master tree. It is just the way they are.

That's not just the only feature that makes wood good for trees but not for animals. Another one is that bones, being alive, can grow with the creature they support. They can even be hollow, as in birds, and so be light and resilient at the same time. If our bones were made of wood, we would have to carry around a large weight of deadwood in the inner part of the bone. That's not a problem for trees which, instead, profit from a heavier weight in terms of better stability. And they do not have to run unless they are the fantasy creatures called "ents."  Spectacular, but Tolkien would need to perform some acrobatic feats of biophysics to explain how some trees of Middle Earth can walk around as fast as humans do.

So, there is plenty of logic in the fact that trees use wood as a structural material. They are not the only creatures doing that. Bamboos (bambusoideae), are also wooden, but they are not trees. They are a form of grass that appeared on Earth just about 30 million years ago, when they developed an evolutionary innovation that makes their "trunk” lighter, being hollow. So, they can take much more stress than trees before breaking and that inspired many Oriental philosophers about the advantages of bending without breaking. Among animals, insects and arthropods use a structural material similar to wood, called "chitin." They didn't solve the problem of how to make it grow with the whole organism, so use it as an exoskeleton that they need to replace as they grow.

Now, let's go to another question about trees. How does their metabolism work? You know that trees create their own food, carbohydrates (sugar), by photosynthesis, a process powered by solar light that works by combining water and carbon dioxide molecules. One problem is that sunlight arrives from above, whereas trees extract water from the ground. So, how do they manage to pump water all the way to the leaves? 

We animals are familiar with the way water (actually, blood) is pumped inside our bodies. It is done by an organ called "heart," basically a "positive displacement pump" powered by muscles. Hearts are wonderful machines, but expensive in terms of the energy they need and, unfortunately, prone to failure as we age. But trees, as we all know, have no muscles and no moving parts. There is no “heart” anywhere inside a tree. It is because only the feverish metabolism of animals can afford to use so much energy as it is used in hearts. Trees are slower and smarter (and they live much longer than primates). They use very little energy to pump water by exploiting capillary forces and small pressure differences in their environment. 

"Capillary forces" means exploiting interface forces that appear when water flows through narrow ducts. You exploit that every time you use a paper towel to soak spilled water. It doesn't happen in human-made ducts, nor in the large blood vessels of an animal body. But it is a fundamental feature in the movement of fluids in heartless (not in the bad sense of the term) plants. But capillary forces are not enough, by far. You need also a pressure difference to pull the water high enough to reach the canopy. That you can attain by evaporating water at the surface of leaves. The water that goes away as water vapor creates a small difference in pressure that can pull more water up from below. This is called a "suction pump." You experience it every time you use a straw to drink from a glass. It is, actually, the atmospheric pressure that pushes the water up the straw. 

Now, there is a big problem with suction pumps. If you studied elementary physics in school, you learned that you cannot use a suction pump to pull water higher than about 10 meters because the weight of the water column cannot exceed the atmospheric push. In other words, you wouldn't be able to drink your coke using a straw longer than 10 meters. You probably never made the experiment, but now you know that it won't work! But trees are far higher than ten meters. You just need to visit your local park to find trees that are far taller than that. 

That trees can grow so tall is a little miracle that even today we are not sure we completely understand. The generally accepted theory for how water can be pumped to such heights is called the “cohesion-tension theory” [8].  In short, water behaves, within some limits, as a solid in the live part of a tree trunk, the “xylem.” The ducts do not contain any air and water is pulled up by a mechanism that involves each molecule pulling all the nearby molecules. The story is complicated and not everything is known about it. The point is that trees do manage to pump water to heights up to about 100 meters and even more. There is a redwood tree (Sequoia sempervirens), in California, that reaches a height of 380 feet, (116 m). It is such an exceptional tree, that it has a specific name “Hyperion.” 

Could trees grow even higher? Apparently not, at least not on this planet. We are not sure of what is the main limiting factor. Possibly, the cohesion-tension pumping mechanism that brings water to the leaves ceases to work over a certain height. Or it could be the opposite problem: the phloem becoming unable to carry sugar all the way down to the roots. Or, perhaps, there are mechanical limits to the trunk size that can support a crown large enough to feed the whole tree. 

Nevertheless, some works of fiction imagined trees so huge that humans could build entire cities inside or around the trunk. The first may have been Edgar Rice Burroughs, known for his "Tarzan" novels. In a series set on the planet Venus, in 1932, he imagined trees so big that an entire civilization had taken refuge in them. Just a couple of years later, Alex Raymond created the character of Prince Barin of Arboria for his "Flash Gordon" series. Arboria, as the name says, is a forested region and, again, trees are so big that people can live in them. More recently, you may remember the gigantic "Hometrees" of the Na'vi people of planet Pandora in the movie "Avatar" (2009).  In the real world, some people do build their homes on trees -- it seems to be popular in California. The living quarters must be cramped, to say nothing about the problems with the static stability of the whole contraption. But, apparently, a section of our fantasy sphere still dreams about the times when our remote ancestors were living on trees. 

But why do trees go to such an effort to become tall? If the idea is to collect solar light, which is the business all plants are engaged in, there is just as much of it at the ground level as there is at 100 meters of height. Richard Dawkins was perplexed about this point in his book “The Greatest Show on Earth” (2009), where he said:

“Look at a single tall tree standing proud in the middle of an open area. Why is it so tall? Not to be closer to the sun! That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss in photons and huge savings in cost. So why go to all that expense of pushing the crown of the tree up towards the sky? The answer eludes us until we realize that the natural habitat of such a tree is a forest. Trees are tall to overtop rival trees - of the same and other species. … A familiar example is a suggested agreement to sit, rather than stand, when watching a spectacle such as a horse race. If everybody sat, tall people would still get a better view than short people, just as they would if everybody stood, but with the advantage that sitting is more comfortable for everybody. The problems start when one short person sitting behind a tall person stands, to get a better view. Immediately, the person sitting behind him stands, in order to see anything at all. A wave of standing sweeps around the field, until everybody is standing. In the end, everybody is worse off than they would be if they had all stayed sitting.”

Dawkins is a sharp thinker but sometimes he takes the wrong road. Here, he reasons like a primate, actually a male primate (not surprising, because it is what he is). The idea that trees “compete with rival trees – of the same and other species” just doesn’t work. Trees can be male and female, although in ways that primates would find weird, for instance with both male and female organs on the same plant. But male trees do not fight for female trees the way male primates for female primates. A tree would have no advantage in killing its neighbors by shadowing them -- that wouldn't provide "him" or "her" with more food or more sexual partners. Killing the neighbors would perhaps allow a tree to grow a little larger, but, in exchange, it would be more exposed to the gust of wind that could topple it. In the real world, trees protect each other by staying together and avoiding the full impact of gusts of wind. 

It doesn’t always work and if the wind manages to topple a few trees, then a domino effect may ensue and a whole forest may be brought down. In 2018, some 14 million trees were destroyed in Northern Italy by strong gales. The disaster was probably the result of more than a single cause: global warming has created winds of a strength unknown in earlier times. But it is also true that most of the woods that were destroyed were monocultures of spruce, plantations designed for wood production. In the natural world, forests are not made of identical trees, spaced from each other like soldiers in a parade. They are a mix of different species, some taller, some less tall. The interaction among different tree species depends on a number of different factors and there is evidence of complementarity among different species of trees in a mixed forest [9], [10]. The availability of direct sunlight is not the only parameter that affects tree growth and mixed canopies seem to adapt better to variable conditions. 

As a further advantage of being tall, a thick canopy that stands high up protects the ground from sunlight and avoids the evaporation of moisture from the soil, conserving water for the trees. When the sun makes the canopy hotter than the soil, the result is that the air becomes hotter higher up, technically it is called "negative lapse rate" [11].  Since the cold air is below the hot air, convection is much reduced, the air stays still, and water remains in the soil. If that's not completely clear to you, try this experiment: on a hot day, scorching if possible, stand in the sun while wearing a thick wool winter hat for several minutes. Then wear a sombrero. Compare the effects. 

So, you see that having a canopy well separated from the ground is another collective effect generated by trees forming a forest. It doesn't help single trees so much, but it does help the forest in conserving water by generating something that we could call a "holobiont of shadows." Each tree helps the others by shadowing a fraction of the ground, below. And that creates, incidentally, the "cathedral effect" that we experience when we walk through a forest. Again, we see that this point was missed by Dawkins when he said that "That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss in photons and huge savings in cost." Another confirmation of how difficult it is for primates to think like trees. 

That doesn’t mean that trees do not compete with other trees or other kinds of plants. They do, by all means. It is typical for a forest especially after an area has been damaged, for instance by fire. In that area, you see growing first the plants that grow faster, typically herbs. Then, they are replaced by shrubs, and finally by trees. The mechanism is generated by the shadowing of the shorter species created by the taller ones. It is a process called "recolonization" that may take decades, or even centuries before the burned patch becomes indistinguishable from the rest of the forest.

These are dynamic processes: fires are part and parcel of the ecosystem, not disasters. Some trees, such as the Australian eucalypti and the African palms seem to have evolved with the specific purpose of burning as fast as possible and spreading flames and sparks around. Have you noticed how palms are “hairy”? They are engineered in such a way to catch fire easily. So much, that it may be dangerous to prune a palm by using a chainsaw while climbing it. A spark from the engine may set on fire the dry wood filaments and that may be very bad for the person strapped to the trunk. It is not that palms could have evolved this feature to defend themselves from chainsaw-yielding monkeys, but they are fast-growing plants that may benefit from how a fire cleans a swat of ground, letting them re-colonize it faster than other species. Note how palms act like kamikaze: single plants sacrifice themselves for the survival of their seed. It is another feature of holobionts. Some primates do the same, but it is rare. 

Other kinds of trees adopt the opposite approach. They optimize their chances for survival when exposed to fire by means of thick bark. The ponderosa pine (Pinus ponderosa) is an example of a plant adopting this strategy. Then there are more tricks: have you ever wondered why some pinecones are so sticky and resinous? The idea is that the resin glues the cone to a branch or to the bark of the tree and keeps the seeds inside. If a fire burns the tree, the resin melts, and the seeds inside are left free to germinate. More evidence that fires are not a bug but a feature of the system. 

In the end, a forest, as we saw, is a typical holobiont. Holobionts do not evolve by the fight for survival that some interpretations of Darwin’s theory had imagined being the rule in the ecosystem. Holobionts can be ruthless when it is necessary to eliminate the unfit, but they aim at an amicable convivence of the creatures that are fit enough. 

The “holobiontic” characteristic of forests is best evidenced by the concept of “biotic pump,” an example of how organisms benefit the holobiont they are part of without the need for hierarchies and planning.



The concept of biotic pump [11] was proposed by Viktor Gorshkov, Anastassia Makarieva, and others, as part of the wider concept of biotic regulation [12]. It is a profound synthesis of how the ecosphere works: it emphasizes its regulating power that keeps the ecosystem from straying away from the conditions that make it possible for biological life to exist. From this work comes the idea that the ecosystemic imbalance we call "climate change" is caused only in part by CO2 emissions. Another important factor is the ongoing deforestation. 

This is, of course, a controversial position. The general opinion among climatologists in the West is that growing a forest has a cooling effect because it removes some CO2 from the atmosphere. But, once a forest has reached its stable state, it has a warming effect on Earth’s climate because its albedo (the light reflected back into space) is lower than that of the bare ground. But studies exist [13] that show how forests cool the Earth not only by sequestering carbon in the form of biomass but because of a biophysical effect related to evapotranspiration. That is, the water evaporates at low altitudes from the leaves, causing cooling. It returns the heat when it condenses in the form of clouds, but the heat emissions at high altitudes are more easily dispersed towards space because the main greenhouse gas, the water, exists in very small concentrations. It may be a minor effect compared to that of the albedo, but it is a point not very well quantified. 

The concept of biotic pump states that forests act as "planetary pumping systems," carrying water from the atmosphere above the oceans up to thousands of kilometers inland. It is the mechanism that generates the “atmospheric rivers” that supply water to lands that are far away from the seas [14]. The biotic pump mechanism depends on quantitative factors that are still little known. But it seems that the water transpired by trees condenses above the forest canopy and the phase transition from gas to liquid generates a pressure drop. This drop pulls air from the surroundings, all the way from the moist air over the sea. This mechanism is what allows the inner areas of the continents to receive sufficient rain to be forested. It doesn’t work everywhere, in Northern Africa, for instance, there are no forests that bring the water inland, and the result is the desert region we call the Sahara. But the biotic pump operates in Northern Eurasia, central Africa, India, Indonesia, Southern, and Northern America.

The concept of the biotic pump is an especially clear example of how holobionts operate. Single trees don’t evaporate water in the air because they somehow “know” that this evaporation will benefit other trees. They do that because they need to generate the pressure difference they need to pull water and nutrients from their roots. In a certain sense, evapotranspiration is an inefficient process because, from the viewpoint of an individual tree, a lot of water (maybe more than 95%) is "wasted" in the form of water vapor and not used for photosynthesis. But, from the viewpoint of a forest, the inefficiency of single trees is what generates the pull of humidity from the sea that makes it possible for the forest to survive. Without the biotic pump, the forest would quickly run out of water and die. It often happens with the rush to "plant trees to stop global warming" that well-intentioned humans are engaged in, nowadays. It may do more harm than good: to stabilize the climate, we do not need just trees, we need forests. 

Note another holobiontic characteristic of trees in forests: they store very little water, individually. They rely almost totally on the collective effect of biotic pumping for the water they need: that's because they are good holobionts! Not all trees are structured in this way. An example is the African baobab, which has a typical barrel-like trunk, where it stores water more or less in the same way as succulent plants (cacti) do. But baobabs are solitary trees, 

Incidentally, evapotranspiration is one of the few points that trees have in common with the primates called "homo sapiens." The sapiens, too, "evapotranspirate" a lot of water out of their skins -- it is called "sweating." But the metabolism of primates is completely different: trees are heterothermic, that is their temperature follows that of their environment. Primates, instead, are homeotherms and control their temperature by various mechanisms, including sweating. But that doesn't create a biotic pump! 

The concept of "biotic pump" generated by the forest holobiont is crucial the correlated one of "biotic regulation," [12] the idea that the whole ecosystem is tightly regulated by the organisms living in it. Natural selection worked at the holobiont level to favor those forests that operated most efficiently as biotic pumps. Plants other than trees and also animals do benefit from the water rivers generated by the forest even though they may not evotranspirate anything. They are other elements of the forest holobiont, an incredibly complex entity where not necessarily everything is optimized, but where, on the whole things move in concert. 

It is a story that we, monkeys, have difficulties in understanding: with the best of goodwill, it is hard for us to think like trees. Likely, the reverse is also true and the behavior of monkeys must be hard to understand for the brain-like network of the tree root system of the forest. It does not matter, we are all holobionts and part of the same holobiont. Eventually, the great land holobiont that we call “forests” merges into the greater planetary ecosystem that includes all the biomes, from the sea to land. It is the grand holobionts that we call “Gaia.” 

References

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