Updated: Aug 16, 2021
Deforestation – ‘the act of cutting down or burning the trees in an area’; a phrase we are all familiar with. But why? What is the real reason for the mass removal of trees? To continue that thought, what are the effects of losing over 50,000 acres of forest every day?
There is no clear answer, because there is not just one reason. However having said that, there are four stand out causes – Beef, soy, palm oil and timber production. Rainforests are heavily relied upon for this production, and as a result are suffering greatly. With 50% of Earth’s plants and animals calling rainforests home, this poses a very obvious problem.
In order to fund our lifestyles across the world, we need resources. Whether it’s clothing materials, building supplies, livestock or crops, they are all required in large quantities due to our growing population. That in essence is why we have created this problem of deforestation. In the case of beef, soy, palm oil and timber production in particular, these all come at a cost for our ecosystems and Earth’s support systems in more ways than one. Soy, palm oil and timber production are significant and increase with our growing need due to population growth, however beef production surpasses them all. When it comes the removal of the trees, there are varying methods with varying primary effects. Which is used depends on why they are being removed, as well as what the left over land will be used for.
Timber production is the fourth greatest cause for deforestation, being responsible for 15% of the annual global greenhouse emissions and it stands out from the top three causes. This is simply because the trees are cut down for their use, not solely for the land. Depending on the method used, the land can be regenerated and on rotation with other areas, can become a ‘permanent’ source for timber. In order to gather wood for paper products (and lower grade lumber), clearcutting (a type of logging) is used. Whereas for higher value wood products and infrastructure, selective logging is required (less damaging to the land and allows regeneration).
In the case of beef, soy and palm oil production, it is the land that is of necessity rather than the trees themselves. With cattle and feed crops, slash & burn is the most common clearance method, with the addition of clearcutting in some cases. These are the first and second leading causes of deforestation – cattle ranching (beef production) first and soy production second. These are also linked, as both are centred around rearing cattle for food. For example, at least 15% of the Amazon alone has been intentionally destroyed, with cattle and feed crops responsible for 80%. And it keeps growing. In the last 20 years soy production has doubled, with 1.2 million acres of land currently being cleared annually in tropical climates, solely for soy production. Of the soy produced, 80% is to be used in animal feed. However, the deforestation for beef production is significantly higher, with 6.7 million acres of tropical rainforest removed for cattle ranching each year. As a result, livestock farming across the world is responsible for the top two causes. Palm oil production is behind at number three on the list. Whilst it seems that it should be higher due to the media coverage it has been getting, it is the growth in its production that is alarming. That being said, all causes need to be addressed urgently.
With an estimated 3.5 – 7 billion trees removed each year (12% of trees needed for enough oxygen at our current human population), our ecosystems and Climate are facing serious problems. Deforestation ‘threatens biodiversity, decreases carbon absorption, magnifies natural disaster damage, and disrupts water cycles.’ But it doesn’t stop there at the primary impacts; there are secondary impacts as a result of the biodiversity loss, for example. As previously mentioned, the level of these threats depends on the type of clearance methods used – clear cutting, selective logging and slash & burn.
Selective logging differs greatly from clearcutting and slash & burn (which in resulting effects are more similar). However, the premise is similar and all have shared features. The first effect is the removal of habit and plant species. All three remove trees, but in vastly varying quantities. Clearcutting and slash & burn removes all trees and vegetation, thus removing all habitats in the area, whilst selective logging doesn’t intentionally remove any plants other than the specific trees. That being said, all require logging tracks for the sites to be reached and timber to be transported away. This means that land has to be cleared, which further damages the forest. The trucks that use these tracks also emit carbon dioxide, which over time builds up to larger quantities.
The water supply is another shared effect. Whilst selective logging leaves most trees in the logging area untouched, there is a thinning effect in the forest canopy. This means that the though-flow will be slightly greater. With clearcutting and slash & burn, the impact is huge, with increased flood risks. It’s the same with the carbon cycle, clearcutting and slash & burn have far greater impacts – for example making the Amazon Rainforest, a vital carbon sink, less of a sink with every passing day. So, what actually are the three methods?
SO, WHAT ACTUALLY ARE THESE THREE METHODS?
Selective logging (a type of logging) is common in timber production for higher value wood products and infrastructure. Whilst it contributes to deforestation, it is seen as more of a sustainable method in relation to the clear cutting and slash and burn, as it is ‘the practice of cutting down a few species of trees while leaving the rest intact and unharmed’. This however, is not strictly true.
Research has shown that only 3% of trees in the selected area are cut down intentionally, as higher quality timber is required, so only certain trees are needed. This is great, as it leaves 97% of the trees standing and the varying plant species protected by the canopy. Knowing this, we would think that ecosystems are left relatively un-impacted. Unfortunately, this is not the case. Whilst only 3% of trees are removed, they are not all contained in one corner of the designated site. This means that people and machinery need to manoeuvre within the unneeded trees to reach the required ones. Then once they have been cut, they of course fall; they fall in a densely packed forest with delicate plant species on the forest floor. As a result, around 49% of trees are unintentionally damaged, as well as vegetation on the forest floor. In addition, this method also contributes to forest fragmentation on a large scale. This essentially means that areas and habitats become unconnected, which can be through the removal of selected trees, but also due to logging tracks and roads linking infrastructure. Whilst it seems small, this can have an effect on forest microclimates, which is ‘the weather in a particular small area, especially when this is different from the weather in the surrounding area.’ It can also make forests more vulnerable to forest fires, which (as explained below with slash & burn) has wider implications.
That being said, in general the area can regenerate without human aid. The unintentionally harmed trees and plant species can recover, as well as regrowth happening relatively quickly – within 50 years. This is because the ecosystem has been left almost untouched (essentially with plants and trees left alone). As a result, wind and animals disperse seeds, nutrients from decomposing leaves of remaining plants are continually supplying the soil, the saplings are protected naturally by the forest canopy, whilst the canopy also filters rain and sunlight; life will not only continue, but will not need to drastically adapt. This is also true for the wildlife, as their habit has not been lost, just reduced. Yes, trees are removed but the area is not cleared, most of the area is left ‘untouched’. For the same reason, compared to other methods, the effect on the global carbon and water cycles are relatively small.
Clear cutting (a type of logging) is common in timber production, specifically with wood to be used for paper products and lower grade wood products. It is also used to expand an area used for cattle grazing and growing crops. This is the preferred timber harvesting method, due to its low cost and efficiency – it’s the most efficient method as there are no trees left standing, as it’s ‘the removal of all the trees in an area of forest.’ In reality however, it’s more than this.
This method not only removes all trees, but also vegetation, no matter what the plant species. As a result the land is left completely bare and exposed. Whilst we know the removal of trees has major on-going negative impacts, unnaturally exposed land is just as bad. To begin with, it cannot be determined how long it will take the area of forest to naturally regenerate, as no plant species remain. No plants means no seed sources, which prevents natural regrowth and recovery. This is major, as the forest is now relying on humans to enable regeneration, requiring the correct re-introduction of native plant species to the exposed soil. But there is a problem with this exposed soil, as well as planting seeds in a large area without protection – the rain. When you take away the trees, the topsoil (upper lay of soil) is exposed and left without protection. This has a significant impact on the water cycle – leaves intercept rainfall, reducing the amount that reaches the forest floor, as well as the speed at which it reaches the ground. So if the leaves are removed, the interception cannot take place. This impacts how the water is returned to the atmosphere as well as what happens to the topsoil.
So what does this mean? Well, everything that could go wrong, will. Firstly, there will be an increase in the amount of water in the soil, for two reasons – water absorption and rainfall. Trees absorb a lot of water from the soil and then transpire, releasing it back to the atmosphere – they hold a lot water, more than their own weight. If there are no trees to absorb this water, their water will just build up in the ground store. Add in the drastic and sudden increase in the amount of water reaching the ground (in the tropics where there is a large proportion of deforestation there is a lot of rainfall) then there is a sudden increase in the amount of water running to the nearest river. This water has a lot of power, meaning that it can carry soil to the rivers. Once the soil reaches the river, it’s deposited by the run-off water that carried it down. If this occurs frequently, it can cause the river to become shallow, thus widening and increase the chance of a flood. This was the case with the Madeira River in 2014, when many areas of the floodplain were engulfed, leading to 68,000 families being evacuated and suffering from disease outbreaks. Impacts of this sediment can also be found in the sea. The flow of the river will move sediments downstream and into the sea, where they will be deposited. Here, these sediments are known to smother coral reefs that are found in shallower waters, which can have significant impacts on ecosystems both in and out of the sea.
Another problem is the topsoil itself. This is a crucial layer for plants and trees, as it has a high concentration of organic matter. Roots of plants and trees use this layer to absorb the much needed nutrients, making it a crucial part of the ecosystem (the tropics tend to have poor and nutrient deficient topsoil). However, without the overhead protection, it is vulnerable to erosion and being washed away by the rainwater. But what’s the significance of this? If there are no trees and plants in the soil, then surely it doesn’t matter that there are no nutrients? Well this is the problem. There are no trees or plants at all. As previously mentioned, the forest relies on humans to plant seeds to allow regeneration to take place. But how can these seeds grow if there are no nutrients that they desperately need? In order to replenish the nutrient store, as a large proportion of the organic matter comes from decomposing plant matter once it’s naturally reached the end of its life, that’s what’s needed. But that’s what can’t grow without the nutrients in the first place. In addition, there is the wind and rain washing away the soil. Without protecting trees and surrounding vegetation, any seeds that got enough nutrients and reached seedlings, are not strong enough to withstand the (now amplified) wind and rain. This is cycle that cannot be broken unless we step in to help.
Noted positives surrounding clear cutting are increased farm land, cost efficiency and an increase in water supply for human and farm animal populations. These are human impacts, they are not natural. The increase in water could be seen as a positive, as there is a growing farm animal population in these areas, but it relation to nature it is unnecessary. The increase in water (used for cattle ranches and crop land) is a direct result of deforestation, which is largely due to a growing demand for this very meat. Therefore, the impacts of this commonly used method are clear and unfortunately, are not good at all.
S LASH & BURN
Slash & burn is the main method of clearing land ready for cattle (beef production) and feed crops. This method is similar to clear cutting in its effects, as it is a method of ‘clearing the land for cultivation, and then, when the plot becomes infertile, the farmer moves to a new fresh plot and does the same again’. This method is essentially an extended version of selective logging, as the trees and plants are first cut down and any organisms are therefore removed (slashed). Once cut down they are not removed, they are simply burnt where they lay. This releases the the minerals and nutrients stored in the plants trees, back into the soil. But these only remain in the soil for a few years, due to the increased exposure to wind and rain, as well as their use in the agriculture. So, once the nutrients are gone, the land is classed as infertile. When this happens, the farmer moves onto a new area of land. This cycle happens every 3 to 20 years.
Slashing the forest has the same outcome and impacts as clear cutting; it is the burning that makes this method different, as this method is used to clear land for another purpose rather that the need for the trees themselves. But the volume of the impacts are greater, as this not only causes habitat fragmentation, biodiversity loss, effects the water cycle and the nutrients in the soil – the carbon cycle effects are amplified through the burning; burning trees releases carbon dioxide and the fires can get out of control and spread, causing more damage. This is one of the reasons why this method is so destructive. During the burning season (June to October) ’20% of the fires in the world can be attributed to deforestation’. These fires release carbon dioxide, as a result of removing the very means in which it can be later removed. Therefore the secondary impact is increase the atmospheric carbon store, as the global tree store us being reduced. To add to that, the lack of soil protection is causing the soil store to erode and further release carbon stored within (stores explained in Our Earth’s Carbon Cycle).
Traditionally, this method was sustainable, as the population was much lower – there was not the demand that we see now. But why was it sustainable then and not now? Well, back then it was possible for farmers to use the land, then leave to farrow for 15 to 20 years. This meant that the land remained untouched and was left to naturally regenerate; the soil’s fertility was reduced from the farming, but the remaining nutrient level was high enough that the vegetation could return, meaning so could the total nutrient level. This is also because the ash from the trees and plants once they had been burned added an additional layer of nutrients to the soil (this is still the case now). Farmers could then use this land once again to farm, or they could leave it to revert to a secondary forest. This is as simple as it sounds, as it’s an area of forest that is able to re-grow back to what it was before a harvest or clearance. It was also common for farmers to split their fields into two. One half would be planted with crops, whilst the other was left farrow. The following year, they would plant crops in the fallow half, leaving the other side to rest or fallow. All of this meant that there was less burning, less destruction and less smoke produced. Unfortunately, this rarely happens now. As farming advanced to supply the growing demand, chemicals, machinery and other tools came on offer to help farmers with land ‘fertility’ and farming in general. As a result, farmers started to stop fallowing their land. However, even with the aid of the chemicals, the land still becomes infertile. So, the farmers do what gives them the most profit – they abandon that area of land (often only after two years) and clear another untouched area. By the early 21st Century, due to the increase in the amount of land being burnt for crops, the areas that had already been abandoned have simply remained in a deforested state unable to naturally regenerate.
So can we fix this growing problem? In theory yes, but it will take a lot of effort. On the whole, selective logging is relatively sustainable. Both clear cutting and slash & burn are not, although they do have the opportunities to be taken in that direction, which is something that needs to happen. The loss of trees in the Amazon Rainforest for example, means that some animals are facing extinction, like the giant otter and Brazilian bare-faced tamarins. Fortunately in some cases, slash & burn for example is carried out more sustainably, but for the majority this isn’t the case and that minority isn’t enough. Overall there are some positives to these clearance methods, but they are mostly negative; after all if the positives are the regeneration of those deforested areas, then that tells us they shouldn’t be cut down in the first place. Other than this, there are no other positives in relation to nature – as mentioned, increased water flow isn’t as good as it seems.
With all the deforestation occurring to allow humans to consume animal meats and other derivatives, it’s clear that we need to address it. With animal welfare rightly becoming more talked about, we should be seeing the reduction of factory farms and an increase in grazing/free-range farms. Whilst this is good for the livestock it is not for the environment and wild animals, as more land will need to be cleared. Our ecosystems and Climate cannot withstand the deforestation rates it’s experiencing now; it cannot take more. The simple solution is for humans to reduce their consumption of animal meats (and other derivatives), otherwise this problem will be unfixable.
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