What You’ll Learn In This Module
- How do trees help climate change?
- A series of same species trees or a forest of mixed species trees. Is there a difference?
- Which forests are best for mitigating climate change?
- What is deforestation? What is forest degradation? and How much forest have we lost?
- What causes deforestation?
- What are Temperate Forests?
- What are Tropical Forests?
- What is forest restoration?
- How can we protect forests?
How do trees help climate change?
Forests cover roughly one-third of the world’s land area, that’s 15.4 million square miles, and play a crucial role in determining the balance of Carbon Dioxide in our atmosphere.
Since trees and plants absorb CO2 from the air and use it to build their leaves, stems, trunks and roots, they are an important carbon sink.
There are around 3 trillion trees growing on the Earth. It’s estimated that they absorb about 2.6 billion tonnes of carbon dioxide every year and have absorbed nearly a third of our emissions since the industrial revolution.
An individual tree absorbs somewhere between 10 and 40 kgs of carbon dioxide per year on average.
The exact amount depends on several factors, such as the age of the tree and the amount of light available for photosynthesis.
Young trees grow faster and absorb CO2 quicker, but older trees are larger and their density means that they can absorb a larger amount of CO2 overall.
About one-quarter of a tree is made up of stored carbon. The ratio of the amount of carbon dioxide a tree absorbs relative to the amount of carbon it stores is about 3.6 to 1.
During the process of photosynthesis, the oxygen in CO2 is released into the air.
A series of same species trees or a forest of mixed species trees. Is there a difference?
There is a difference, but it’s not related to how much carbon dioxide they will absorb.
Wherever you plant a tree, it will take carbon from the atmosphere.
The faster trees grow and the larger they grow, the more carbon they suck down from the atmosphere.
But a mixed-species forest is a thriving community, and it offers many more benefits to the natural world besides carbon absorption.
It supports a whole series of interactions that a series of individual trees cannot.
Besides carbon dioxide absorption and carbon capture, forests can:
- house whole ecosystems of fauna and flora,
- provide extensive areas of intrinsic natural beauty,
- significantly reduce the risk of floods,
- purify rivers,
- reduce urban air pollution,
- provide a host of benefits to human wellbeing and recreation
- provide income for local communities
- provide timber for wooden buildings which can hold carbon captured for centuries
Which forests are best for mitigating climate change?
The most valuable forests for fighting climate change are the primary forests.
These are forests that are very wild, old and dense. They have huge, mature trees with full canopy cover, plus a great deal of varied undergrowth.
They can be found on five of earth’s continents and make up about one-third of the world’s forests.
Examples include the Great Bear Rainforest of British Columbia, and the forests of the Amazon, Indonesia and the Congo.
Primary forests are one of the greatest houses of biodiversity on the planet.
And they store about 200 billion tons of carbon.
Yet, they are still being cut and damaged, sometimes under the pretence of being ‘sustainable’.
Researchers argue that once a primary forest is cut by humanity, even under ‘sustainable’ methods, the forest begins to degrade.
What is deforestation? What is forest degradation? and How much forest have we lost?
Deforestation is the permanent destruction of forests and woodlands and the conversion of forests to non-forest uses.
Forest degradation is when forests are damaged or weakened, reducing their ability to produce a healthy ecosystem.
It’s difficult to know the full extent of deforestation.
The world’s land surface has been monitored since 1972. The analysis of land use has shown that forests have been removed over this period. Estimates include:
- The World Resources Institute (WRI) says that 30% of the world’s forests have been cleared and another 20% have been degraded.
- According to estimates of the United Nations Food and Agriculture Organisation, some 13 million hectares of forest – or 15 billion trees – are lost every year.
- Estimates by the World Wildlife Fund suggest that an area of forest the size of 48 football pitches is lost every minute.
- In 2017, over one football pitch of forest was estimated to have been lost every second – the second highest rate recorded since 2001.
- In the last 60 years, more than half of the tropical forests worldwide have been destroyed.
For climate change alone, deforestation and forest degradation are a big problem.
When trees are burned or left to decay, they release all the carbon dioxide they had stored into the atmosphere.
Alongside the carbon lost from the trunks and greenery of trees above the surface, carbon is also lost from the roots and soil below the ground surface.
The loss of carbon is larger and faster when fire is used to clear the trees and in peatland areas where the soil is very carbon-rich.
Forests are rapidly disappearing around the world and one-third of CO2 emissions from land-use change are caused by deforestation.
But it’s not only the carbon that is lost.
When forests are destroyed, humanity loses the intrinsic beauty of the forest and its biodiversity, sometimes people lose their livelihoods and cultural underpinnings, together with food, medicine, shelter, heat and timber.
They also lose the natural means of providing clean air, regulating the water cycle and preventing soil erosion.
Europe cleared many of its forests from the 17th to 20th centuries and the US did the same in the 19th and 20th.
The centre of deforestation in the 20th century has been Central and South America, Southeast Asia and Africa, which produce around 90% of land-use-change emissions.
What causes deforestation?
Deforestation in local communities is often the result of a complex interaction of many drivers.
These include poverty and inequality, commerce, cultural habits, urbanization and changes in land use, natural hazards, corruption, subsidies and even local government policy.
At a global scale, it’s estimated that about three-quarters of global deforestation is driven by commercial or subsistence agriculture.
The land on which forest grows is often considered more valuable than the standing forest itself.
Throughout history, whenever we needed to produce more food, humanity has cut down the forest.
And deforestation today usually starts with logging.
Forests are then cleared and burned, being replaced by agricultural crops such as soya beans and rubber or by pasture for cattle.
A big driver of forest clearing has been the production of palm oil.
You can find Palm oil in a huge number of everyday products, including soaps, shampoos, chocolate, bread and even crisps.
It’s an incredibly versatile and efficient crop.
But natural forest habitats continue to be cleared and disappear in order to make space to grow oil palm trees.
Losing these forests, coupled with the land-use change away from carbon-rich soils, means that millions of tons of greenhouses gases are released into the atmosphere, contributing to climate change.
About 10% of deforestation is because of natural hazards such as forest fires.
Each year, and around the world, hot and dry weather leads to forest fires.
These burn millions of hectares of forest worldwide, alongside threatening human life and property and increasing air pollution.
A certain amount of fire helps to clear undergrowth and release the seeds of certain trees species. It’s part of a forest’s natural life cycle.
But climate change, with its increased temperatures, heatwaves and drought, is supercharging these natural fires.
An increase in their frequency and severity has occurred over the last two decades in some areas and it’s likely to continue in the years ahead.
But while the cause of forest fires can be natural, direct human action also plays a significant role.
Fires may result from both human neglect and intent. Small fires can get out of control.
In areas of deforestation, the number of fires has closely followed the deforestation rate for the last two decades.
‘Slash and burn’ practices are common in some regions to clear forests for arable land.
Besides the damage by the surface removal of trees, deforestation breaks up the forest ecosystem, altering the forest’s role in regulating the climate and creating a drier environment, with a greater risk of future fires.
Infrastructure, mining and industrial wood production cause the remaining 10% of deforestation.
The construction of infrastructure, such as roads, can affect forests through two routes.
First, the direct effect of clearing space for the road and second, the indirect effect of breaking open a forest and opening up access to it for settlement and agriculture.
Mining projects are often accompanied by major infrastructure construction such as road, railway lines and power stations, adding further demands on forests and their water ecosystems.
Finally, illegal and unsustainable logging occurs in all forests across all continents and destroys wildlife and the livelihood of local communities, besides destroying the forest.
What are Temperate Forests?
Temperate forests are one of the four main types of forest around the world: tropical, subtropical, temperate and boreal.
Temperate forests experience all four seasons. They grow between 30 and 50-55 degrees latitude, mostly in the northern hemisphere.
A quarter of the world’s forests lie in this zone, making up 1.9 billion acres in total.
They can include coniferous forests, full of evergreen trees with leaves all year; fully deciduous forests that shed their leaves every autumn, or a mixture of the two.
Temperate forests have a smaller variety of animal and plant life compared to tropical or subtropical forests because of their cold winter temperatures.
Until the 19th century, these forests were heavily deforested. Now they are increasing again. Some are in conservation zones, while other degraded areas have been repaired and are now better managed.
The temperate forest zone is now a net carbon sink, absorbing 0.8 gigatons of carbon each year and with rising biomass density.
It’s estimated that over 1.4 billion acres could still be restored, which would increase the capacity of these forests to absorb carbon further.
While not facing the threat of large-scale deforestation, these areas are fragmented by development.
And they face major threats from climate change.
These include hotter temperatures and longer heatwaves, more frequent floods, more severe wildfires, as well as new and more frequent pest and disease attacks.
What are Tropical Forests?
Tropical forests are found between 23.5 degrees north and 23.5 degrees south of the equator.
They are very wet areas, receiving more than 200cm of rainfall per year.
They are home to gigantic trees and a vast variety of animals. About 80% of the world’s documented specifies can be found in these forests.
These forests cover the largest area of all the four forest groups and face the most extensive land-use change.
Deforestation is most concentrated in tropical rainforests. They once covered around 12% of the world’s land surface, but now they cover about 6%.
They have suffered from clearing, fragmentation and damage, resulting in a loss and depletion of plants and trees.
Tropical forests also take up the most carbon, as much as 6 gigatons of carbon dioxide per year, while facing also the greatest uncertainty.
But the damage and loss of trees in these areas are emitting around 16% of greenhouse gas emissions.
Restoration efforts are increasing.
Over 1 billion acres are ready for the full restoration of large forests with dense canopy cover.
What is forest restoration?
Forest restoration means taking actions to help a damaged forest ecosystem recover and regrow in its original nature.
What is important is not simply the number of trunks, but also the quality of the forest.
Reforestation includes actions to restore healthy trees, native organisms and species; to recover a thriving forest community that allows native animals and birds to return, and to build up the forest’s health and capacity to be net carbon stores.
It can include protecting the forest alongside cultivating, weeding and planting techniques.
The process of restoration takes time.
It takes on average over 65 years to recover 90% of the biomass and re-sequester the carbon that was lost so quickly through burning and deforestation.
Over 2 billion hectares of forest have the potential to be restored worldwide.
While not the same as old forests, restored forests support the water cycle, conserve and protect the soil, provide habitats for animals and insects, and food, medicine, homes and income for local communities.
Restoration supported by local communities helps to ensure that the restoration is well designed and addresses the causes of the original forest damage while helping to underpin a restoration’s long-term success.
The 2011 Bonn challenge set a target to restore 370 million acres (150 million hectares) of forest worldwide by 2020.
In 2014, the New York Declaration on Forests added a cumulate target of 865 million acres (350 million hectares) to be restored globally by 2030.
These targets would help forests to store an extra 12 to 33 gigatons of carbon dioxide.
But the total cost of the target lies between 350 billion and 1 trillion dollars, which cannot be borne by the mainly low-income countries in the tropical regions.
Much progress on the restoration of forests will therefore rely on funding from the wealthier world nations.
How can we protect forests?
Protective measures can include:
- Better governance and improved enforcement of existing laws
- Public policies which maintain and care for forests, rather than give incentives for their destruction
- The creation and enforcement of anti-logging laws
- The protection of indigenous lands
- Empowering forest communities to protect their forests
- Better access to finance and technologies for the surveillance and protection of forests
- Sustainable forestry and certification programs
- Payments for the protection and maintenance of forest land
- Preventing fire, erosion and grazing in forest areas
Protecting a forest to prevent its loss is always better than trying to bring the forest back into an area of e.g. agricultural land.
This is because a restored forest takes many years to establish itself and it never fully recovers its original biodiversity, structure, and complexity.
The extent of deforestation in the world today has had also significant social, economic and environmental effects, not only locally but also globally.
The benefits of forest protection are many. They include:
- The protection of entire ecosystems of fauna and flora,
- The protection of extensive areas of natural beauty,
- Reducing the risk of floods,
- Purify rivers,
- Reducing urban air pollution,
- Providing a host of benefits to human wellbeing and recreation
- Providing income and non-timber goods and services for local communities
- Providing sustainable timber for wooden buildings which can hold carbon captured for centuries
There are several large programs that reward nations for the conservation of forest carbon stocks and reducing deforestation and degradation.
These include the United Nations Reducing Emissions from Deforestation and Forest Degradation (REDD+) program, the New York Declaration on Forests and the Forest Carbon Partnership Facility.
But it is important that also the people who live at the edge of forests have the support that encourages also the value and protection of standing forests.
Competing and conflicting demands for land are likely to increase towards 2050 when it’s estimated that over 9 billion people will live on Earth.
Want to know why there hasn’t been more action on climate change? Read about why climate change is difficult to address and how you can make a difference.