Take a straw poll on the street today and ask anyone about trees and you will likely hear one of the following sound bites (or many variations thereof):
It all sounds very reasonable and plausible. But guess what? NONE OF IT IS TRUE. This is a very controversial thing to state, so let’s flesh out the details a little.
Let’s begin by considering the first two points as one – that trees are the ‘lungs’ of the Earth and that they ‘breathe’ CO2. We’ll start by analysing briefly what ‘breathing’ actually is.
In all mammals, birds and animals – take humans for example – our lungs take in air from outside and, in return, carbon dioxide (CO2) is expelled back out again, in greater volumes than is originally inhaled. But why do we breathe air at all? Why can’t we just function without it, perhaps relying on the food we eat and the water we drink for all our energy and other bodily needs?
Well, it is because we are made up of much smaller parts – our cells. These cells require high value, instantly accessible energy in order to carry out their duties inside our bodies. It is our cells, then, that actually require the oxygen that is in the air and which we transport to them in dissolved form via our bloodstream. Once they have used the oxygen for energy, CO2 accumulates in the bloodstream, as it is produced during the process. This CO2 is then transported back to our lungs via the bloodstream, and we breathe out again. Phew!
The energy contained in oxygen is not enough on its own to sustain a human being, however, as a far more industrious energy is required to move us around and preserve our basic metabolic functions than can be provided by it alone – food – and that is where our cells come in once again. They require the O2 we breathe in, in order to provide the initial energy to begin converting sugars (that are also dissolved in our blood) into hard-core, useable kinetic energy that can help us fight, run and play, whenever we need it. These sugars, or hydrocarbons, come from the food we eat and the water we drink. The oxygen we breathe is therefore simply a ‘catalyst’ – fuel for the cell itself, to allow it to convert these sugars into useful, human-sized energy.
So, back to trees.
Trees use a process that all plants use to grow and sustain themselves: photosynthesis. Photosynthesis requires three key components to work efficiently – water, CO2 and sunlight. Water (H2O) is required by the tree for the hydrogen it contains. The hydrogen combines with carbon from the CO2 the tree also absorbs to create long chemical chains, also known as hydrocarbons, of which sugars and cellulose are a class and is ultimately what the tree is made of (we call it ‘wood’). So what about the sunlight – why is that needed for the process? Well, just like a human cell requires energy to fuel its own processes, the tree also needs energy for its cells to function, and it gets this energy from the Sun.
Sunlight is the catalyst that provides the energy and allows the chemistry of the tree to split the hydrogen from the oxygen in water and combine it with the carbon that, in turn, splits from the oxygen in the CO2. The ‘waste’ product, as we know, is oxygen. For this process to happen, two water molecules combine with one carbon dioxide molecule to produce one hydrocarbon molecule and two oxygen molecules. The chemical formula, then, is: H2O + H2O + CO2 => H4C + O2 + O2
As sunlight to trees is analogous to the role oxygen plays in humans, it is far more metaphorically, if not anatomically, accurate to say that trees therefore ‘breathe’ sunlight – and not CO2. Furthermore, as the CO2 and water components provide the carbon and hydrogen that ultimately forms part of a new cell wall (more wood) it is also much more metaphorically and biologically accurate to say that trees eat CO2.
These are important distinctions. Often when one thinks of a tree ‘breathing’ it is easy to assume that it is a constant process (like real breathing) and that throughout its lifetime a tree will ‘breathe’ out a lot of oxygen – right up until the day it dies – and thus help to replenish atmospheric stocks of O2. It is this analogous breathing that has earned the tree the reputation of being the ‘lungs’ of the Earth. But, as we have just examined, it is more accurate (if this metaphor is to be used at all) to say that trees are the ‘stomach’ of the Earth – and stomachs get full.
When a tree is fully grown, it simply stops eating. At best it consumes just enough CO2 for general maintenance and annual foliage growth cycles, but any CO2 sequestration advantages are lost when this foliage is littered back to the ground and inevitably decomposes. A mature tree is therefore ‘carbon neutral’ – that is, it produces no more oxygen than its decomposing biomass gives off CO2.
Imagine putting a tree in a room where there is no CO2. What will happen? Well, because there is nothing for the tree to grow new cells with, after a few weeks or months it will likely wither and die. Now imagine what would happen to the same tree if it were deprived of sunlight? In a permanently dark room, the tree would fail to photosynthesise. This means its cells would be deprived of the energy it needs to metabolise and the tree would rapidly die. It would literally ‘suffocate’.
This might seem like a trivial distinction to have to make, to show that trees breathe sunlight and not CO2, but there are some people who actually believe that a tree really breathes and that the gas it ‘inhales’ is CO2. There are also some people who believe, and I quote, “without trees we’d have no air to breathe”. This alarming suggestion brings us nicely on to our third point for discussion, which is the assumption that ‘without trees there would be less (or no) oxygen’.
When we think of trees, especially in their natural settings, such as woodlands or forest, we can’t help but think of all the ‘nasty’ CO2 they are absorbing and all the lovely fresh oxygen they are pumping out into the air. However, there is a balance in nature that is always struck. For every emitter of O2, there is an absorber of it, hungry and waiting to consume it.
Take human beings once again. We emit between 0.5 and 1 kilograms of CO2 per day. If we take the average of these, it equates to c. 270 kg’s of CO2 each year. This is an average, then, for every man woman and child. An average tree that lives to be 100 years old will absorb about 5,000 kg’s of CO2 in its lifetime. This equates to 50 kg’s of CO2 each year. So, in order for the 270 kg’s of CO2 breathed out by a single human to be offset by trees alone, would require: 270 / 50 = c. 5 trees.
This is worth restating. Five trees are required to offset the CO2 emissions of just one human being. Now, living in the natural forests, temperate forests, rain forests and woodlands are species of marsupials, bears, squirrels, birds, animals, and (of even greater relevance to this particular discussion) insect and bacterial life-forms. The forests are literally teeming with millions upon millions of oxygen breathing creatures, occupying every natural ecological nook and cranny.
Every living tree provides a natural habitat for oxygen breathing life and, although there are no exact figures available, it is likely that the number of life forms a single tree can support is exactly balanced by the CO2 / O2 gas exchanges between them. Moreover, if it were not so, that the emission of O2 by plant life is exactly balanced by the CO2 emissions of animal life, then our planet would have run out of oxygen or CO2 long, long ago. Therefore, not only is this balance overwhelmingly likely, it is actually necessary to explain continued life on Earth.
This is not to say that a given tree will suck in the CO2 that the actual bird living in its branches will breathe out, or the actual bear scratching its back against the bark, but that there is a balance in nature that would forbid surplus habitation of non-plant life forms in the forested areas of the Earth due to this simple constraint
Furthermore, the most veracious of oxygen feeders are the smallest life forms of all – bacteria. These small creatures are the dustbins of the natural world, consuming vast quantities of dead biomass and other materials littered on the ground and they are prevalent everywhere. A colony of bacteria can consume an entire fallen tree and return all of its carbon stock, as CO2, back into the atmosphere in a matter of months, under the right conditions. So we can confidently say that animal and plant life – the oxygen breathers and CO2 consumers of the planet – are in a perfect, symbiotic, ecological balance.
In other words, the more trees there are, the more animal and insect life there is. These life forms ensure that no matter how many trees there are on the Earth, there could NEVER be a surplus of oxygen (or a deficit of CO2) as their consumption of O2 is in perfect balance with the trees production of it. Conversely, if one were to chop down half the trees on Earth it would likely destroy half of the natural habitat of these forest-dwelling creatures, thus killing them off in the process and retaining the balance of gaseous exchanges between other animal life and their tree hosts.
Moreover, if all of the trees on Earth were chopped down, it would be truly catastrophic for habitats and morally and ethically repugnant, but, in terms of oxygen levels, it would hardly make one jot of a difference.
No trees = no woodland and forest habitats = no woodland and forest life forms = no CO2 respiration emissions from biological life forms.
So without trees there would be oxygen – moreover, the same amount of oxygen.
Now let us look at the fourth point of discussion, that ‘trees are a permanent store for carbon’. Trees are a store for carbon. They do it by absorbing CO2, mixing it with water and building cells made of complex sugars, using the Sun’s energy to drive the process. It is called photosynthesis and, in a tree, we call the end product ‘wood’.
Wood is about 50% carbon by dry weight. Burn it, and the carbon would combine with two oxygen atoms in the atmosphere to form CO2, so for each kg of carbon stored in a tree, it is equivalent to approximately 3.6 kg’s of CO2 that has been sequestered from the atmosphere.
This is a good thing (for oxygen breathers at least) but the tree is by no means unique in this respect. All plants do precisely the same thing. Every flower, blade of grass and thorny bush is a store for carbon, just like a tree. The difference between most other plants and trees is the amount of time the carbon resides within its cellular structure – nothing more.
A blade of grass might last a few months; a hedgerow, a few years. A rose bush might last 30 years in a garden if it is well looked after. Only trees are more durable. Trees can last 100, 200 or, in some very extreme cases, 500 years or more. However, if we take an average age of a tree to be about 100 years, say, then the carbon that is locked up inside it will remain locked up only for this duration. For the avoidance of any doubt, and to educate the ‘trees really breathe’ fraternity further (who may be starting to ask a few hard questions by now), the mass of carbon stored in a tree at the end of its life is the total carbon it has ever removed from the atmosphere and the total oxygen it gave back in return, is no more than this process would naturally allow.
Once a tree dies, it will succumb to decomposition.
This act of rotting is not the tree succumbing to the forces of nature – wind and rain, and the like; it is actually being eaten by bacteria. Nothing is wasted in nature and the trees carcass becomes a feast for millions of hungry ‘mouths’. These bacteria breathe in oxygen and breathe out CO2. So as the tree decomposes, all of the CO2 it once captured is released back into the atmosphere.
It is true that a tree is a store for carbon, but it is a transient store, one that, in geological timeframes, is the blink of a metaphorical eye. In fact, if geological timeframes are used as a measure for the efficacy of all plants as stores for carbon, then trees are no better than grasslands for CO2 sequestration. It means absolutely nothing to say that the trees contain more carbon than grass, as this carbon will all be released back into the atmosphere in good time.
So, trees are not a permanent store for carbon.
Let’s now move to our final point of discussion that states ‘deforestation directly contributes to global warming’. It has already been discussed in detail (above) that the removal of trees, whilst being deplorable in terms of loss of habitat and damaging the Earth’s natural beauty, does not alter global warming to any great extent. More trees mean more creatures; and more creatures mean more CO2. It’s a perfect balance that doesn’t have any climate altering affects. What does alter the climate, however, is the human propensity and desire for burning fossil fuels.
Fossil fuels were created millions of years ago when dead plants and trees that had fallen to the floor became buried. In these unique conditions, rather than decompose, the biomass compacted and became compressed and, over eons, became coal and oil. By burning these fuels today, we are extracting energy that was embedded in its chemistry tens of millions or even hundreds of millions of years ago. In doing so we are upsetting the natural balance of nature and adding CO2 into the atmosphere at a rate that has begun to change our climate.
Deforestation, wood products, recycling, paperless offices – none of these things either help, or hinder, or are responsible in any way for climate change.
We are responsible – because we burn fossil fuels.
And the only way we can stop it is to reduce our reliance on fossil fuels and find new ways to remove CO2 from the atmosphere and put carbon safely back into the ground from where it came. Just how we might be able to do this is bullet pointed below (please refer to the diagram to the upper right for the corresponding carbon flow) and more details can also be found here:
- Carbon is sequestered from the atmosphere by trees.
- The trees are felled and chopped into wood.
- The carbon stored in the wood is stabilised and fixed inside paper products.
- This paper can be used for entertainment and communication purposes.
- The paper is placed into long-term, underground storage (i.e. landfill).
- The paper remains in landfill indefinitely and becomes part of the Earths natural composition over thousands of years.