In the West, another massive tree planting initiative, TeamTrees, is gaining momentum. Even Elon Musk joined her, changing his name on Twitter to Trilon Musk. Mass plantings are believed to help combat global warming. As we will show below, in fact, everything can be exactly the opposite.
At first glance, the tree planting initiative looks logical. The press reports almost every day: the area of forests on the planet is shrinking, many times more trees are cut down than planted.
At the same time, it is clear that they are needed for the production of oxygen. Contrary to popular belief, the sea is no longer the main source of oxygen: the organisms living there have too negligible biomass. Trees account for almost 400 billion tons of all carbon in living organisms on Earth, and all marine life - only six billion tons. Trees are clearly more important to the biosphere and atmosphere: that is, saving them by planting millions of new ones is a good idea.
However, if an idea seems like a good idea, sometimes it is worth thinking about it a little deeper. Perhaps everything is not as straightforward as it seemed at first.
How many trees do you need to plant to change something
Let's start with the basics: the TeamTrees project plans to plant 20 million trees, and Elon Musk has allocated funds for a million. How many trees are there on the planet? Will a million or 20 million be enough to really help nature?
Oddly enough, no one really knows how many trees there are on Earth. As eminent researchers write in a 2015 article in Nature: "Trees play a key role in our understanding of the earth's biosphere" - but how many there are in this biosphere is not very clear.
Interestingly, this scholarly work grew out of a story similar to Trilon Musk and the TeamTrees green initiative. Thomas Crowter, the first author of a 2015 article, had an eco-activist friend. He was part of a group that wanted to plant a billion trees. Note: not 20 million like TeamTrees, but a whole billion. One problem: they first formulated a goal, and only then they thought about it. As Crowther notes, “They didn't know what planting a billion trees would bring. Will it increase their number in the world by 1%? Or 50%? They didn't even know if it was even possible to place one billion trees on Earth."
Knowing that Crowther was a scientist, his friend asked: how many trees are there on the planet? Alas, the scientist could not immediately answer the question. The scientific papers that he found on this topic looked like pure theorizing, without attempting sufficiently complete field measurements. The least theoretical estimate was made from a rough estimate based on satellite imagery. Alas, they have such a resolution that you can't see a separate tree there, but it's better than nothing. The estimate said: there are 400 billion trees on the planet, 60 per person.
It turned out that a billion trees would not only change anything, but in general would be somewhere on the verge of a measurement error. To find out for sure whether a friend's eco-initiative was really so hopeless, Crowther and his comrades sat down and counted for themselves. To do this, they took data on the density of individual forest areas (summed up measurements for 400 thousand surveyed areas) and multiplied them by the total forest area of this density, calculated from satellite photos.
And then it turned out that it would be better for a friend not to ask Crowter at all. The work done by him showed: there are more than three trillion trees on the planet, four hundred per person.Moreover, Crowther and Co admit that their estimate can easily be greatly underestimated. They found normal field data only for North America and Europe, where, to be honest, the forests are much less dense than in the tropics. Another scientific work in the Amazon alone counted 290 billion trees. It may very well be that due to the greater density of the forest in the tropics of trees on the planet, it is strongly over three trillion.
Against this background, what is the billion new trees of that now forgotten eco-initiative? Approximately 0.033%. And what does 20 million trees from the newfangled TeamTrees project mean? That's right: one hundred and fifty thousandth. The million trees for which Trilon Musk has allocated money is only one three million of the total number of trees on the planet.
The same work in Nature reports that five billion trees are added to the world every year. That is, a very loud publicized environmental campaign plans to do 1/250 of what is already done every year. Only those who plant the bulk of these billions do not advertise on Twitter and YouTube. Often these are logging companies, which are obliged by the law of many countries to compensate for the felled with new plantings. Conclusion: not all those saviors of the planet who are loudly broadcasting about this.
The good thing about history is that it clears the minds a lot. At school, we were told that science has already studied the Earth well. In life, it turns out that science believes that there are either 400 billion trees, or three trillion, or a lot more, but how many is unknown, because outside of developed countries, normal field research is not very much where it is conducted. Maybe you should think about the rest of the "common truths" about trees? Isn't there the same kind of fortune-telling and isn't the real picture different from the one that the media tells us?
How quickly forests disappear
The media reports that forests are rapidly shrinking. The same is said by the Intergovernmental Panel on Climate Change. She also calls for an end to the disappearance of forests. But at what specific rate do they disappear?
The UN reported in 2005 that 130 thousand square kilometers per year are lost. In 2016: that only 33 thousand square kilometers of forest per year. Obviously, at some point in the organization they were wrong, but at what point? Is there any independent data?
There is. Global Forest Watch, the Washington-based World Resources Institute's forest tracking program, says 290,000 square kilometers of forest were lost in 2016 (two Vologda Oblasts). The discord is getting stronger.
It looks like the time has come to stop trusting the numbers of organizations that do not publish their calculations in peer-reviewed scientific journals and turn to serious scientific articles on the topic. What do they say, how fast are forests being destroyed?
In 2018, an article was published in Nature, where changes in forest area were first calculated based on satellite images immediately in tens of years, and not in a few years, as before. According to them, it turned out that in 1982-2016 the forests increased by 2.24 million square kilometers - that is, their area grew by 64 thousand square kilometers per year. An increase is observed in the subarctic (taiga, including Russian), subtropical and temperate (including Russia) zones. In contrast, the rainforest has declined slightly, mainly due to active logging in Brazil.
Previous work was often based on cadastral information from various countries about which area was forest and which was cut down. Inventories are compiled by people who do not always work quickly or thoroughly. They are often too lazy to quickly list the forest area overgrown with trees. Moreover, today you have included it in the category of "forest", and tomorrow you will have to appoint foresters there and monitor the absence of illegal logging and other things. Officials are also people, and with a fixed pay they naturally try to work less.
Satellite images are not lazy: they capture the objective reality.But if you use satellite images only for several years, like the Global Forest Watch, then only fresh clearings will be visible on them, but territories that have been overgrown with trees over the years will not be visible: after all, according to classifications, only objects above five meters are considered trees, and for in a matter of years (and even in a dozen years), not all newly grown trees will reach this height. Since the work of 2018 used images immediately over 35 years, it recorded not only felling, but also their subsequent overgrowing with trees, which made it possible to observe the real picture.
We have already written about why forests - like terrestrial vegetation in general - are expanding. Let us briefly recall that the main reason for this is the rapid increase in the concentration of CO2 in the atmosphere over the past decades. Fires can undoubtedly slow down this process, but only slow it down. The fires began 420 million years ago, immediately after the plants came to land, and during this time the plants have adapted well to the threat of fire. They suffer from it losses of only thousands of square kilometers per year, which is much less than the annual increase.
Interestingly, the world's media are remarkably immune to the scientific picture of the world. An article in Nature says that forests grow by 2.5 Tula regions a year? It doesn’t matter: the media is still trumpeting about the destruction of forests, on Wikipedia exactly the same thing is happening. "UN News" has come to the point that the forests on their pages "disappear" at a rate of 70 thousand square kilometers a year - although in special publications of UN bodies they "disappear" only 33 thousand square kilometers a year. How does this fit together? In the same way as with the growth of forests observed from space: not at all.
However, let's not find fault with the world media: we'd better take a look in the mirror. Russia added 790,000 square kilometers of forest between 1982 and 2016, far more than any other country, including the frantic tree planting China. How much have you heard about this in the Russian press? We would venture to assume that about zero times. The science? Facts? Forget it. The news should have a good clickable headline. For example (all titles are real): “Siberian forests are dying. At the sawmills, Russians fight the Chinese. " Or: "Our forests are burning down." At worst, it's simple: "Forests are dying in Russia."
Trees: the best and most secretive manipulators on the planet
Until recently, many innocent questions about trees did not have precise answers. Scientists recently found out not only the number of trees, but also the fact that they are stepping on the outside world, and not retreating in front of it. A dozen or two years ago, there was no understanding of how well trees, in fact, are well organized and how deeply they control the world around them.
Many trees familiar to us from childhood, including birches, oaks and pines, are in direct contact with each other by their roots. Contacts are maintained for a reason: through them, trees exchange water and nutrients. Often they are connected in large networks, through which substances are transferred to the sides of the original tree for tens of meters.
This makes sense: in a small depression there may be an excess of moisture, in a clearing nearby - its deficiency, and nitrogen and phosphorus in the soil are often unevenly distributed. In such a situation, it is rational to share one plant with another, especially since over time a neighbor can respond with the same service. Often, cooperation takes place even between trees of different species growing nearby.
The scale of this "forest communism" is extremely wide. Young trees at the bottom of the forest ocean receive a little light and would perpetually die on their own from lack of nutrients. Receiving sugar synthesized by adult trees (through the contacts of root systems), they can live and grow to an adult state - after which they themselves will begin to feed the young.
Trees also have an analogue of “pension provision”: many stumps of trees felled long ago in stable forests can remain alive for years (or even start new shoots).Stumps do not have leaves; by themselves, they would quickly die. Only due to the fact that the surrounding trees feed their old acquaintance with sugars, this does not happen.
The "root web" is not only for the exchange of food. Through it, there is an exchange of chemical (including through the mediation of plant hormones) and even electrical signals. Yes, you heard right: with electrical signals - the same as in the nervous system of animals (although the voltage and frequency of electrical impulses, of course, differ slightly in trees).
By the way, in the root systems of some tree species, sounds emitted by plants with a frequency of about 220 hertz, inaudible to humans, are even spread (the soil absorbs them well). She informs the surrounding trees that they have a disease or that they are attacked by pests. Having received a signal, other trees immediately change their behavior so that it is more difficult for pests to attack them.
Plant pests are not only insects, but also larger animals. When a giraffe in the savannah approaches an acacia and begins to chew on its leaves, it immediately releases ethylene - a "sign" of negative stress. Neighboring acacias are far away, so it is not always possible to connect with them through the roots. However, ethylene is carried by the wind - and they immediately begin to pump tannins into the leaves, making them tasteless for herbivores.
Giraffes approach acacias from the leeward side so that neighboring plants do not smell ethylene from what is being eaten. However, if there is no wind (capable of carrying ethylene away from neighboring acacias), they have to, after slightly pulling one tree from the group, walk a hundred meters to another, which has not yet had time to prepare for a chemical counterattack on the herbivore.
Trees are not limited to creating a lesonet and introducing social security for young and old. They still actively influence the world around them. When elms and pines attack caterpillars, they emit substances that attract parasitic wasps, which lay their eggs directly in the caterpillars.
But controlling the behavior of the wasp is, generally speaking, trifles. More interestingly, the trees control the rain. Recall: in air without small particles (condensation centers of droplets in clouds), water vapor itself will begin to form droplets only at temperatures around minus 13 ° C. At more human temperatures, clouds will appear only when the relative humidity is much higher than 100%. As the physicist Igor Ivanov accurately notes, "in real conditions such a strong satiety almost never occurs."
It is not hard to guess: if the clouds arose only in this way, the rains would have been much less, and in some places they could have stopped going altogether. How is it that it rains on the planet at all?
It's all about particles about ten thousandths of a millimeter in size, serving as the center of condensation of water droplets. When the air is dry, they provoke the formation of water droplets; when it is humid, they can, on the contrary, "slow down" the condensation of droplets and thereby reduce precipitation. The number of such particles in the air ranges from one thousand to ten thousand per cubic meter. Accordingly, the probability of rainfall changes with formally the same amount of moisture in the atmosphere.
According to modern estimates, there are 12.9 trillion tons of water in the planet's atmosphere, but the overwhelming majority (at least 99%) is contained outside the clouds, in the form of transparent water vapor. That is, by controlling the number of particles that provoke moisture condensation in the atmosphere, you can dramatically change the amount of clouds, as well as precipitation.
As the reader has already understood, plants produce a mass of particles that serve as centers of condensation. For example, such is pollen, as well as those particles into which it decays over time: they serve as effective condensation centers for water vapor. This means that plants can generate more clouds even in the air with the same amount of water vapor.
It's not just pollen. Entering the coniferous forest, we feel a fresh scent.It is mainly formed by pinene - an important component of pine resin, which pines (and not only them) actively emit into the atmosphere. In 2016, it was shown that pinene particles serve as excellent condensation centers for clouds. The authors of this work believe: "Even today, trees produce most of the centers of cloud condensation over wooded areas with seemingly clean air."
According to the results of experiments, the presence of a pine forest on the surface of the planet doubles the density of the clouds above them. As a result, not only does the level of precipitation increase, but also the thermal regime changes dramatically. On a summer day, such places heat up less, but at night they give off heat more slowly. In autumn, the increased cloud density tends to slow down the seasonal temperature drop.
Commanded by the winds
And that's not all of the mechanisms by which trees control rain and clouds. In 2017, the Proceedings of the National Academy of Sciences published a work where for the first time it was possible to show that plants can saturate the atmosphere with water vapor so that the clouds above them will become much larger than usual. The effect was recorded over the Amazonian jungle.
When new leaves begin to actively grow on local trees - two to three months before moist winds from the Atlantic come - they evaporate water so vigorously through the stomata (small pores on the lower side of the leaf) that they saturate the air with moisture, triggering formation over overcast jungle. The fact that the culprit is precisely the plants, it was possible to find out thanks to deuterium. There is little of it in the water brought by ocean winds: water molecules, in which instead of hydrogen - deuterium, evaporate poorly. But when it is thrown into the air by a plant, it brings out both ordinary and "heavy" water.
But that is not all. When water thrown by plants over the Amazon condenses into clouds, it releases latent heat into the surrounding atmosphere. The heated air rises up, and moist sea air "flows" in its place. That is, plants, in fact, "suck" moist sea air masses into the South Amazon, forming long-term stable winds that dominate here throughout the rainy season. Along the way, over the surface of the Atlantic, the air becomes drier, which is why sea water evaporates more actively, saturating the atmosphere with new water vapor.
Let us ask ourselves the question: what will happen to the climate if the Amazon jungle is completely cut down? Obviously, the water vapor in the air of this part of the Earth will also decrease. Meanwhile, water vapor is a more efficient greenhouse gas than carbon dioxide. The latter plays an important role in high latitudes, especially in winter, because the cold air can contain only a small amount of water vapor. But in the latitudes of the Amazon, water vapor is the main "insulator" of the planet. Without the selva and air, which saturates its actions with moisture, the heat from there will go out into space at night more actively than now. This region will receive a less warm climate.
Then the question arises: is planting trees really an effective way to combat global warming?
The other side of the influence of trees on the climate is their color. All scientists agree that the albedo (reflectivity) of a broadleaf forest is noticeably lower than that of the steppe, tundra, and meadows. In a coniferous forest, this difference is tens of percent. There are also estimates according to which the albedo in Alaska can be 7, 1%, and on the tundra - 19, 9%.
Meanwhile, if the reflectivity of the landscape is reduced by one percent, then it receives more energy from the sun - about 40 kilowatt-hours per year. Suppose the difference in albedo between forest and steppe (or tundra) is only one percent. This is a gross understatement, in fact, the difference is greater, but let's close our eyes to that.
Let's go back to the TeamTrees initiative. It is clear that 20 million trees are about nothing. But let's say we took and planted trees at once on a million square kilometers of steppes and meadows - and they all grew.What will happen to the earth's climate and us? You calculated correctly: the Earth will absorb 40 trillion kilowatt-hours more solar energy, which will heat up more.
One might argue that 40 trillion is not much, only double the total electricity consumed by mankind in a year. Well, it's true. But climate is a sensitive thing, and often warming can spur even a small push.
Also, remember that in the real world, trees can reduce the albedo of the Earth's surface much more than 1%. For example, in Israel, on the outskirts of the Negev Desert, a small pine forest was grown (no watering!). The albedo of the desert is about 30-35%, and that of the pine forest is a couple of tens of percent less.
If we plant millions of square kilometers of deserts with forests, the Earth's thermal budget will grow by hundreds of trillion kilowatt-hours a year. That is, a consistent fighter against global warming should wake up in a cold sweat at the thought of planting forests in the desert, like the Israeli successful experiment.
By the way, this applies not only to tropical deserts. Back in 2010, it was calculated that the overgrowth of the Arctic tundra with trees, which is inevitable during strong warming, will lead to the saturation of the air with water vapor (emitted by plants). As a result, "this greenhouse effect will melt the sea ice due to additional water vapor." After that, the surface of the Arctic will become even better at absorbing solar energy, further spurring warming.
Why trees are not storage for CO2
You can often hear that trees bind carbon dioxide, which is how they fight global warming. There is some misunderstanding here. Treelike plants bind CO2 perfectly and for a long time in the Carboniferous period. The forests were constantly flooded, a dead plant many meters high fell into the water, from where its carbon was no longer extracted. That is why such a period is productive in terms of coal.
However, by the end of the Carboniferous period, the suction of CO2 from the atmosphere brought the climate to glaciations (very rare in the history of the Earth, if you do not take the last two million years). The cooler world has less rainfall. Trees stopped growing in solid swamps, and mushrooms have learned to decompose wood, releasing its carbon back into the atmosphere. Forest fires and insect pests are actively working in the same direction. The results may be a little surprising: those Canadian forests that are subject to regular monitoring and measurement are now emitting more CO2 than they absorb.
Yes, trees can ultimately bind more CO2 than they absorb. But the amount of long-term binding of this kind is not that great. It is not clear today whether this influence of trees on the climate is compensated by other factors. For example, the fact that forests absorb more solar energy than other vegetation landscapes, or that they increase cloudiness.
Fight Global Warming Trees - How to Maintain Your Garden with a Goat
Let's summarize. There are a lot of trees in the world, and the promoted pop-initiatives to plant a million or a billion trees will not really change anything in the climate of our planet.
But everything will change if people like Musk and other wood-lovers find out that there are trillions of trees in the world and start planting them in large quantities. Based on what is known to science today, it is likely that trees can significantly contribute to the growth of the planet's thermal budget - just as they contribute to cloudiness and precipitation. It is worth recalling: from the point of view of trees, there are no downsides to global warming. This means that as it increases, the growth of forests (all other things being equal) will be more active.
Fossils of past hot eras (even the Carboniferous period, even the Mesozoic with the Miocene) show that the warmer the Earth, the more trees there are on it. Their metabolism works fast enough only when temperatures exceed 20 degrees.Of course, they will not mind global warming, not only up to 17 degrees (this is expected by the end of the century), but up to plus 21 (this coincided with the maximum distribution of forests in the past).
Trees are very effective, albeit unconscious, regulators of the environment in which they live. If there are enough of them, they know how to get from it the sea winds they need, increased clouds. Trying to stop global warming with their help is like trying to stop corruption with the help of a corrupt politician. Of course, a corrupt politician absorbs bribes, that is, at first glance, other corrupt officials will get less of them (the pockets of business are not bottomless). But in reality, the environment created by the bribe-taking fighter is such that everyone else will start taking more.
The fact that trees bind CO2 for the duration of their life (although after death they release most of it into the air) does not mean that they stop warming. The way they affect the environment around them with clouds and high absorption of solar energy increases the Earth's thermal budget, rather than decreasing it.
Should you cut trees to fight global warming?
Let's make a reservation: we are not calling to fight trees to save the planet from climate change. As we already wrote, warming in itself on a modern scale is not a catastrophe. Moreover, there are a number of clear advantages behind the trees. Although they increase the Earth's thermal budget, they also evaporate moisture in summer, locally softening the heat.
They effectively reduce noise pollution, and it is forests that contain the planet's most species-rich ecosystems. Therefore, if you are worried about the environment, then yes, you can and even need to plant trees - around cities and in them. This is where there is no man, forests grow easily, but around cities, thanks to the construction of new roads and housing (as well as man-made fires), not many of them grow.
But the idea of planting forests widespread in the media about combating global warming is a dubious idea from a scientific point of view. Based on what is known today, it will be more of a fight for warming than against it. Perhaps that is why Musk quickly removed the first letters of Trilon's name from his page?