How Trees Work For Us

When you hear the word “TREES”, what picture does it conjure in your head?
To most, it is a picture of majestic tree trunks with canopies of green leaves.
It is automatically soothing and relaxing, particularly if you put it into the context of a forest with some undergrowth or a tree lined street. If you add birds, bees and other animals living in and around the trees it adds to this scene of tranquillity and sheer pleasure.

This scenario has been used by the health professionals for decades. They know that this soothing assists in the recuperation process and reduces mental stress. Climate change has aggravated stress which has been worsened by Covid. Trees will compensate.

A stress free brain enhances the health of the body, reduces violence, and hence lower drug abuse, which could contain criminal activity. It is a fact of life, treed suburbs have less crime.
Furthermore the aesthetics of the tree and the cool shade underneath encourages social interaction and provides better quality of life.
And let us not forget the tree’s ability to absorb noise, thus reducing noise stress.

There are other solid reasons for the positive perception of trees.
Let us itemise them and relate them to everyday terms.
To start with, leaves are green, which is the most soothing colour in the spectrum.
This colour is due to the chlorophyll in the leaves which reflects all light except for those energy bands needed for the photosynthesis reaction, which equates to the green wave band.

Green leaves produce food by photosynthesis, which takes place in the myriads of production sites throughout all green leaves, each of which resides is a complex molecule called chloroplast. The process of photosynthesis is very complex, but in simple terms it is combining 6 molecules CO2 with 6 molecules of water to produce one molecule of sugar and 6 molecules of oxygen.
This is universal for all green leaves, whether they are grasses, shrubs (incl. fynbos) pines or broadleaf.
Hence water use is not related to the specie, but rather to the number of chloroplast molecules. It stands to reason those plants and trees with more leaves will use more water.

The sugar produced is the foundation stone for all food created in the universe. Once produced each specie will modify this sugar for its own growth and survival. It is transported via its vascular system (the cambium) to where it is needed, whether it is the trunk, branches, roots, flowers, fruits, seeds etc.
The important point to realise is that, like all living entities, there is a central control for growing the tree and ensuring its sustainability.

The CO2 is obtained from the air which enters the leaves via the stomata. The water is sucked up from the ground via its root system. The energy for the reaction comes from light. These are brought together within the chloroplast onto the surface of an enzyme called Rubisco, allowing the reaction to be completed. The sugar is used as in above paragraph and the oxygen leaves via the stomata.

This is one of the most important functions of green leaves. It converts 6 molecules of CO2, a green house gas into 6 molecules of oxygen i.e. it converts a toxin into an essential life sustaining product.
Let’s put this in perspective, there is only 0.04% of CO2 in the air and the leaf can manage to make the foundation stone for all foods throughout the world from this small concentration of air.
Think about it. 0.04%… to grow all the billions of trees and shrubs … that is sophisticated technology! By comparison, the animal kingdom absorbs their life-sustaining oxygen from the air, of which there is 21%. Easy peasy.

Let’s turn to the water delivery. Trees can be 5 m. – 100 m. tall and the leaves are at its extremities. The tree must suck the water up this incredible height every second…. Let that sink in. If we had to pump water 5 m. or 20 m. up it would require a high power pump and it would be very costly. The tree does that effortlessly via its vascular system. Again nature has some incredible technology!

The air coming into the leaf has many pollutants, such as nitrous oxides, sulphur oxides, Particular Matter (a carbon particle), and a range of chemicals and metals from fossil fuel as well as toxins from agricultural and factory productions. The toxic metals include mercury, lead, chromium, cadmium etc.
Most of these are poisons to mankind and the body cannot dispose of them. So they accumulate in organs and can reach dangerous levels. Hence taking them out of the air is very beneficial.
A proportion of these toxins are locked into the biomass of the tree. Hence the tree is really a store of carbon and pollutants – with an attractive bark and canopy.

These pollutants will stay there for the life of the tree until it is felled or burned.
When this happens all these pollutants are released to the air, poisoning the air we breathe.
That is a disaster and should be prevented!
Did you know that deforestation all over the world contributes 13 – 15%  of green house gases, and increases the other pollutants?

To combat this poisoning of the air has been a major problem. Scientists eventually convinced politicians and the captains of industries of the threat and they made promises at the Paris Climate Accord to enforce limits to this pollution.
However, the fossil fuel lobby managed to derail the good intentions. Instead, use of these fuels has continued to increase. The scientists had another try at COP 26. The outcomes here were simple. Stop fossil fuels usage, stop felling trees and plant more trees. That includes SA.
Let’s see what happens now…

Coming back to photosynthesis, there is a problem with the process. The enzyme at the centre, Rubisco, is heat sensitive. Its efficiency increases with temperature until it reaches 35 C, when it starts to plateau and decrease as the enzyme becomes denatured. At 45 C Rubisco stops functioning and the world’s food production stops.

Nature to the rescue!
All vegetation has been provided with another technology –its own airconditioner.
Just like our own home air conditioner, except it does not use fossil fuel and does not push hot air into the atmosphere.
Nature uses water only, which is sucked up to cool the leaves internally.
But this is not enough in hot climates. So a portion of the water is exuded through the stomata to create an envelope around the plant or tree like an external airconditioner. This helps to reduce the ambient temperature by 4 – 8 C.

This is a bonus for biodiversity including mankind, because this moisture ensures not only a lower temperature for less heat stress, but also ensures an efficient functioning of our lungs and bodies. Hence we can breathe easily and our whole body benefits from better health.

Nature’s airconditioners provide a huge economic benefit, but there is a negative.
It stands to reason that the bigger the plant or tree, the greater the volume of water is used.
The cost of water must be offset against the cost of airconditioning an open air space 10 m. high.

Let us follow the water to the roots. For water to be effective it needs to have a healthy porous soil. Roots are instrumental in providing this.
Roots trap the underground water, creating good conditions for the underground biodiversity to develop.This has two advantages viz. it allows rain falling on the surface to be absorbed into the soil, and assists the root hairs in an efficient absorption of water into the tree with the support of the fungal network.

This has further advantages, a healthy root system not only anchors the tree firmly in the soil, but also slows down the underground water flow to prevent erosion thus overcoming a potential economic disaster.
However, in urban environments, mankind has countered these advantages!
For their own convenience they cast concrete and tar over all the porous soil, preventing water being absorbed with the result that this water rushes downhill accumulating into torrents and floods, doing untold damage to roads, buildings, cabling and water pipes.
The worst part is that it is limiting the water content of the soil to the detriment of the vegetative biodiversity.

Good underground water reserves are essential for sustainability of the ecosystem, where trees act like recycling machines bringing the ground water into the atmosphere for use by all vegetation and animals.

Let me summarise the benefits.
Nature has provided incredible technology in the workings of the tree, which has been doing a phenomenal job over the millenniums maintaining the balance of nature by providing food, a healthy environment and a habitat for animal diversity.
On top of this it adds to the aesthetics of the world. We must respect trees and forests. Focus on preserving them and all its biodiversity.

Finally, let me detail all the benefits that we experience every minute of the day, and how trees make our life worthwhile, improve our quality of life, and reduce our health bills and utility costs:

1. Soothe and relax – reducing mental stress, leading to less violence and crime
2. Absorb noise – reducing noise stress
3. Reduce temperatures by 4 -8 C – reducing heat waves/heat stress and making our living space cool
4. Absorb GHG – reducing major causes of global warming
5. Absorb pollution – reducing health risks e.g. respiratory, heart, brain damage
6. Exude oxygen – restoring the oxygen balance for all biodiversity
7. Moisture in air – lowering temperature and boosting overall health by iImprove body functioning especially lungs and skin
8. Reduce soil erosion – conditioning soil, reducing stormwater and underground damage
9. Support biodiversity at all levels – above and below ground
10. Recycle water from below-ground to above-ground (refer 4. and 6.) – a giant recycling machine
11. Provide food and habitat for biodiversity

It is impossible to put a value on all these health and utility benefits, but the value far exceeds maintenance and replacement costs of trees.
To top it all, the ambience of trees creates immeasurable value for social interaction and quality of life. They really make you feel good. And they are a good investment.

Address by Henk Egberink, a retired chemist and Exco member of TreeKeepers