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There are an estimated three trillion trees on Planet Earth. Prior to human civilization, there may have been around six trillion. The loss by half is largely attributed to deforestation for agriculture, urban development, and resource extraction over thousands of years.
The extent of this reduction highlights significant ecological impacts, including loss of biodiversity, alterations to water cycles, and contributions to climate change due to reduced carbon sequestration.
In the contemporary discourse on climate change, the reduction of forests stands out as a critical issue with far-reaching implications. Forests are not only vital carbon sinks but also crucial to biodiversity, water cycles, and the livelihoods of many communities worldwide.
Forests play a pivotal role in regulating the Earth’s climate. As carbon sinks, they absorb carbon dioxide from the atmosphere through photosynthesis. This process mitigates the greenhouse effect, which is primarily responsible for climate change. Rainforests, often referred to as the “lungs of the Earth,” are particularly efficient at carbon sequestration. For instance, the Amazon Rainforest alone is responsible for absorbing millions of tons of carbon emissions annually. However, when these forests are cut down, not only is this carbon sequestration halted, but the stored carbon is also released back into the atmosphere, exacerbating global warming.
The loss of forests globally is alarming. Rainforests in regions like the Amazon, Congo Basin, and Southeast Asia have been particularly affected by logging, agriculture, and mining. Similarly, the boreal forests, which ring the northern latitudes of the globe, are not only being cut down but are also increasingly impacted by climate change itself, leading to issues like increased fire frequencies and insect infestations that further diminish their density and health.
During the day, trees absorb CO2 from the atmosphere and, using sunlight as energy, convert it into glucose (a sugar) and oxygen through photosynthesis. This process occurs mainly in the leaves where chlorophyll is present.
Unlike photosynthesis, respiration occurs both day and night. During respiration, glucose is broken down with the consumption of oxygen to produce energy for the tree’s cellular activities. This process releases CO2 and water as by-products.
Respiration in trees involves numerous biochemical processes that take place within the mitochondria, the energy powerhouse of the cell.
Glucose derived from photosynthesis is broken down into carbon dioxide and water in the presence of oxygen, releasing energy stored in ATP (adenosine triphosphate) molecules. This energy is crucial for various cellular functions and overall tree growth.
‘Maintenance Respiration’ is the energy required to sustain the basic functioning of living cells, including nutrient uptake, growth regulation, and repair. ‘Growth Respiration’ involves the energy used specifically for the synthesis of new tissues such as leaves, branches, and roots.
What determines the rate of tree respiration? Two main factors are temperature and environmental stress. Respiration rates generally increase with temperature up to a certain point. As for environmental stress, such factors as drought, nutrient deficiency, or pest attacks can influence respiration rates, usually causing them to increase as the tree expends more energy to cope with stress.
When a forest’s trees are respiring more carbon than they are photosynthesizing, it is a net carbon source, no longer a sink.
The question of whether certain forested areas act as net carbon sinks or sources is being closely examined through ongoing research. The specific status of different forests can vary widely based on numerous factors, including forest type, management practices, climate conditions, and disturbances such as fires or logging.
Forests generally act as carbon sinks when they absorb more carbon dioxide than they emit. Unfortunately for us, when forests are disturbed or are subject to deforestation, they often become carbon sources, releasing more stored carbon back into the atmosphere. Several forested areas around the world have transitioned from being net carbon sinks to net carbon sources. Here are some key examples:
Amazon Rainforest: Once the largest carbon sink in the world, parts of the Amazon Rainforest have become carbon sources. Deforestation for agriculture and ranching, combined with the impact of droughts and fires, has diminished its ability to absorb carbon dioxide. Recent studies suggest that deforested areas in the eastern Amazon are now emitting more carbon than they absorb.
Boreal Forests of North America: The boreal forests across Canada and parts of Alaska have experienced increased fire frequency and intensity due to warmer and drier conditions fueled by climate change. These fires not only release large amounts of stored carbon but also reduce the forest’s overall capacity to sequester carbon in the future.
Southeast Asian Forests: In countries like Indonesia and Malaysia, extensive peatland forests have been drained and converted for palm oil production. When peat (which is highly carbon-rich) is drained and exposed to air, it oxidizes and releases significant amounts of carbon dioxide. Additionally, the frequent fires in these regions exacerbate carbon emissions.
Forests in Central Africa: Similar to the Amazon, parts of the Congo Basin are experiencing shifts from carbon sinks to carbon sources. Factors include logging, land conversion for agriculture, and localized climate changes affecting forest health and growth.
In recent years, the frequency and intensity of wildfires have increased significantly, becoming a global concern. These fires are often exacerbated by a combination of factors including climate change, deforestation, and human activities. Wildfires not only lead to the immediate loss of forests but also contribute significantly to the release of stored carbon dioxide, further enhancing the greenhouse effect that drives global warming. The boreal forests, known for their resilience in cooler climates, are now experiencing more frequent and severe fires due to rising temperatures and drying conditions.
Similarly, rainforests, which were once too wet to burn frequently, have seen an increase in fire incidents, particularly in areas where the forest has been degraded by logging or cleared for agriculture.
There are also ongoing debates about the effectiveness of reforestation and afforestation in different regions, the long-term impact of climate change on forests’ ability to store carbon, and how best to manage forests sustainably.
In response to the dire implications of deforestation, several international commitments have been made to restore forest canopies. Prominent among these is the Bonn Challenge, established in 2011, which aims to restore 350 million hectares of deforested and degraded land by 2030. This initiative is significant as it represents a practical, large-scale investment in natural climate solutions. Restoration under the Bonn Challenge includes a mix of reforestation (replanting trees in deforested areas), afforestation (planting trees in areas that were not previously forested), and the natural regeneration of forests. These efforts are crucial for enhancing biodiversity, improving water cycles, and expanding carbon sinks.
Countries from Brazil to Indonesia have pledged millions of hectares to this cause. Afforestation efforts, as part of the broader restoration initiatives, have been implemented in many regions, from large-scale projects in China and India to community-driven efforts in Sub-Saharan Africa. Despite these efforts, the overall loss of forest cover continues in many parts of the world, driven by agricultural expansion, illegal logging, and the development of infrastructure. The net effect is that while some areas see new growth, globally, forests continue to be lost at an alarming rate.
In recent years, the frequency and intensity of wildfires have increased significantly, becoming a global concern. These fires are often exacerbated by a combination of factors including climate change, deforestation, and human activities. Wildfires not only lead to the immediate loss of forests but also contribute significantly to the release of stored carbon dioxide, exacerbating the greenhouse effect that drives global warming.
The boreal forests, known for their resilience in cooler climates, are now experiencing more frequent and severe fires due to rising temperatures and drying conditions. Similarly, rainforests, which were once too wet to burn frequently, have seen an increase in fire incidents, particularly in areas where the forest has been degraded by logging or cleared for agriculture.
Reforestation is a complex process that involves more than just planting trees. It requires a sustainable approach that considers local ecosystems, biodiversity, and the needs of indigenous communities. The new trees need to be planted soon to offset the rate of carbon emission effectively. Ideally, reforestation projects should begin immediately to maximize their impact on carbon absorption and climate mitigation. The younger forests, however, do not sequester carbon at the rate of mature forests, emphasizing the importance of preserving existing old-growth forests alongside planting new ones.
The promises made by countries to restore forest canopy are not just environmental commitments but also crucial for global climate health. The urgency with which these new trees need to be planted cannot be overstated. Climate scientists argue that major reforestation efforts need to be implemented within the next decade to effectively combat the worst effects of climate change. This includes not only planting new trees but also implementing policies that reduce deforestation and increase the resilience of existing forests.
Afforestation and reforestation efforts in compensating for lost forests are vital, but they often cannot immediately replace the ecological complexity and carbon storage capacity of mature forests. Additionally, young plantations are more susceptible to threats such as fires and pests compared to old-growth forests. Therefore, while afforestation is beneficial, it is not sufficient on its own to stop the negative impacts of widespread deforestation.
To truly mitigate the effects of climate change and the increasing incidence of wildfires, a multifaceted approach is needed. This approach should combine aggressive protection of existing forests, especially old-growth forests, with sustainable management practices and restoration efforts. Additionally, addressing the root causes of deforestation—such as the demand for agricultural land and timber—requires global cooperation and robust policy frameworks. Only by tackling these issues holistically can we hope to see a net gain in forest cover and a decrease in the global warming potential associated with forest loss.
While the Bonn Challenge and other reforestation initiatives are critical, they must be part of a broader strategy that includes conservation, sustainable management, and a reduction in the drivers of deforestation to effectively address the complex interplay of issues affecting global forests and climate.
While international commitments to forest restoration are a step in the right direction, the pace and scale of these efforts need to be significantly increased. For reforestation to be part of a successful climate change mitigation strategy, it must be implemented rapidly and sustainably, respecting ecological, social, and economic contexts. The time to act is now, as the window to mitigate the worst outcomes of climate change is rapidly closing. •
This is a first overview of articles in the series about Forest Policy. We will be presenting an article in each issue of the magazine for at least the next year. These, plus a few other previously published articles constitute the “syllabus” in Forest Policy Advocacy which, when completed, will yield a certificate and a one-year free membership in Project Save the World. See page ___ for details. As with other articles here, you are welcome to comment here: https://tosavetheworld.ca/global-warming-2/#comments