Forests cover 31% of the land area on Earth. Every year, 75,700 square kilometers (18.7 million acres) of the forest is lost.[14] There was a 12% increase in the loss of primary
tropical forests from 2019 to 2020.[15]
Deforestation has many causes and drivers. Examples include agricultural
clearcutting, livestock
grazing,
logging for timber, and
wildfires.
A study suggests that "tropical, arid and temperate forests are experiencing a significant decline in resilience, probably related to increased water limitations and climate variability" which may shift ecosystems towards
critical transitions and
ecosystem collapses.[17] By contrast, "boreal forests show divergent local patterns with an average increasing trend in resilience, probably benefiting from warming and CO2 fertilization, which may outweigh the adverse effects of climate change".[17] It has been proposed that a loss of resilience in forests "can be detected from the increased temporal autocorrelation (TAC) in the state of the system, reflecting a decline in recovery rates due to the critical slowing down (CSD) of system processes that occur at thresholds".[17]
23% of tree cover losses result from wildfires and climate change increase their frequency and power.[20] The rising temperatures cause massive wildfires especially in the
Boreal forests. One possible effect is the change of the forest composition.[21] Deforestation can also cause forests to become more fire prone through mechanisms such as logging.[22]
Effects of deforestation on climate change aspects
According to a review, north of 50°N, large scale deforestation leads to an overall net global cooling while tropical deforestation leads to substantial warming not just due to CO2 impacts but also due to other biophysical mechanisms (making carbon-centric metrics inadequate). Irreversible deforestation would result in a permanent rise in the
global surface temperature.[23] Moreover, it suggests that standing tropical forests help cool the average global temperature by more than 1 °C.[24][25]
Deforestation, particularly in large swaths of the Amazon, where nearly 20% of the rainforest has been clear cut, has climactic effects and effects on water sources as well as on the soil.[30][31] Moreover, the type of land usage after deforestation also produces varied results. When deforested land is converted to pasture land for livestock grazing it has a greater effect on the ecosystem than forest to cropland conversions.[32] Other effect of deforestation in the Amazon rainforest is seen through the greater amount of carbon dioxide emission. The Amazon rainforest absorbs one-fourth of the carbon dioxide emissions on Earth, however, the amount of CO2 absorbed today decreases by 30% than it was in the 1990s due to deforestation.[33]
Modeling studies have concluded that there are two crucial moments that can lead to devastating effects in the Amazon rainforest which are increase in temperature by 4 °C and deforestation reaching a level of 40%.[34]
Decrease in climate services
Human activity such as deforestation for livestock grazing and fuel wood has led to forest degradation and over extraction resulting in ecosystem biodiversity loss. Loss and degradation of forest has a direct impact on the Earth's diverse flora and fauna and, therefore, on climate change because they are the best defense against CO2 buildup in the atmosphere.[35][36][37] If there is more foliage photosynthesizing more CO2 will be absorbed, thereby balancing the potential temperature increases.[38]
Forests are nature's atmospheric
carbon sink; plants take in atmospheric carbon dioxide (a
greenhouse gas) and convert the carbon into sugars and plant materials through the process of
photosynthesis.[39] The carbon is stored within the trees, vegetation, and soil of the forests. Studies show that "intact forests", in fact, do
sequester carbon.[40] Examples of large forests that have a significant impact on the balance of carbon include the
Amazonian and the
Central African rainforests.[41] However, deforestation disrupts the processes of carbon sequestration and affects localized climates. Additionally, cutting down trees plays a role in a positive
feedback loop centered around climate change on a much larger scale, as studies are finding.[40]
When a climate changes, this causes the shift in a species' geographic range in order to maintain the climatic conditions (temperature, humidity) it is accustomed to. Ecological zones will shift by approximately 160 km per 1 degree Celsius.[38] A reduction in the area of any habitat, but particularly in forest habitat along with climatic change, enables species invasion and the possibility of biotic homogenization as stronger invasive species can take over weaker species in a fragile ecosystem.[38] Humans will also be impacted by the loss of biodiversity as food, energy, and other 'ecosystem goods and services' patterns are disrupted.[42]
Burning or cutting down trees reverses the effects of carbon sequestration and releases greenhouse gases (including carbon dioxide) into the atmosphere.[41] Furthermore, deforestation changes the landscape and reflectivity of earth's surface, i.e. decreasing
Albedo. This results in an increase in the
absorption of light energy from the sun in the form of heat, enhancing
global warming.[40]
Changes in rainfall
As a consequence of reduced evapotranspiration, precipitation is also reduced. This implies having a hotter and drier climate, and a longer dry season.[43][44] This change in climate has drastic ecological and global impacts including increases in severity and frequency of fires, and disruption in the
pollination process that will likely spread beyond the area of deforestation.[44][43]
According to a study published in 2023, tropical deforestation has led to a significant decrease in the amount of observed precipitation.[45] By the year 2100, researchers anticipate that deforestation in the Congo will diminish regional precipitation levels by up to 8-10%.[45]
Statistics have shown that there is a direct correlation between forest fires and deforestation. Statistics regarding the
Brazilian Amazon area during the early 2000s have shown that fires and the air pollution that accompanies these fires mirror the patterns of deforestation and "high deforestation rates led to frequent fires".[46]
The
Amazon rainforest has recently experienced fires that occurred inside the forest when
wildfires tend to occur on the outer edges of the forest.[15]Wetlands have faced an increase in forest fires as well.[15] Due to the change in temperature, the climate around forests have become warm and dry, conditions that allow forest fires to occur.[15]
Under unmitigated climate change, by the end of the century, 21% of the Amazon would be vulnerable to post‐fire grass invasion. In 3% of the Amazon, fire return intervals are already shorter than the time required for grass exclusion by canopy recovery, implying a high risk of irreversible shifts to a fire‐maintained degraded forest grassy state. The south‐eastern region of the Amazon is currently at highest risk of irreversible degradation.[47]
According to a study in tropical peatland forest of Borneo, deforestation also contributes to the increase in fire risk.[48]
Control measures and their effects on climate change
Trees absorb carbon dioxide (CO2) from the atmosphere through the process of
photosynthesis. Throughout this biochemical process, chlorophyll in the tree's leaves harnesses sunlight to convert CO2 and water into glucose and oxygen.[49] While glucose serves as a source of energy for the tree, oxygen is released into the atmosphere as a byproduct. Trees store carbon in the form of biomass, encompassing roots, stems, branches, and leaves. Throughout their lifespan, trees continue to sequester carbon, acting as long-term storage units for atmospheric CO2.[50] Sustainable forest management, afforestration, reforestation and proforestation are therefore important contributions to climate change mitigation.
Afforestation is the establishment of a forest in an area where there was no previous tree cover.
Proforestation is the practice of growing an existing
forest intact toward its full ecological potential.[51] An important consideration in such efforts is that the carbon sink potential of forests will saturate[52] and forests can turn from sinks to carbon sources.[53][54] The
Intergovernmental Panel on Climate Change (IPCC) concluded that a combination of measures aimed at increasing forest carbon stocks, and sustainable timber offtake will generate the largest carbon sequestration benefit.[55]
In terms of carbon retention on forest land, it is better to avoid
deforestation than to remove trees and subsequently reforest, as deforestation leads to irreversible effects e.g.
biodiversity loss and
soil degradation.[56] Additionally, the effects of af- or reforestation will be farther in the future compared to keeping existing forests intact.[57] It takes much longer − several decades − for reforested areas to return to the same carbon sequestration levels found in mature tropical forests.[58]
There are four primary ways in which reforestation and reducing deforestation can increase carbon sequestration. First, by increasing the volume of existing forest. Second, by increasing the carbon density of existing forests at a stand and landscape scale.[59] Third, by expanding the use of forest products that will sustainably replace fossil-fuel emissions. Fourth, by reducing carbon emissions that are caused from deforestation and degradation.[60]
The planting of trees on marginal crop and
pasture lands helps to incorporate carbon from atmospheric CO 2 into
biomass.[61][62] For this carbon sequestration process to succeed the carbon must not return to the atmosphere from biomass burning or rotting when the trees die.[63] To this end, land allotted to the trees must not be converted to other uses and management of the frequency of disturbances might be necessary in order to avoid extreme events. Alternatively, the wood from them must itself be sequestered, e.g., via
biochar, bio-energy with carbon storage (
BECS), landfill or stored by use in construction.
Reforestation with long-lived trees (>100 years) will sequester carbon for substantial periods and be released gradually, minimizing carbon's climate impact during the 21st century. Earth offers enough room to plant an additional 1.2 trillion trees.[64] Planting and protecting them would offset some 10 years of CO2 emissions and sequester 205 billion tons of carbon.[65] This approach is supported by the
Trillion Tree Campaign. Restoring all degraded forests world-wide would capture about 205 billion tons of carbon in total, which is about two-thirds of all carbon emissions.[66][67]
Although a bamboo forest stores less total carbon than a mature forest of trees, a
bamboo plantation sequesters carbon at a much faster rate than a mature forest or a tree plantation. Therefore, the farming of bamboo timber may have significant carbon sequestration potential.[68]
During a 30-year period to 2050 if all new construction globally utilized 90% wood products, largely via adoption of
mass timber in
low rise construction, this could sequester 700 million net tons of carbon per year,[69][70] thus negating approximately 2% of annual carbon emissions as of 2019.[71] This is in addition to the elimination of carbon emissions from the displaced construction material such as steel or concrete, which are carbon-intense to produce.
As enforcement of forest protection may not sufficiently address the drivers behind deforestation – the largest of which being the production of beef in
the case of the Amazon rainforest[72] – it may also need policies. These could effectively ban and/or progressively discourage deforestation-associated trade via e.g. product information requirements, satellite monitoring like the
Global Forest Watch, related
eco-tariffs, and product certifications.[73][74][75]
Reforestation, afforestation and agroforestry
Possible methods of reforestation include large-scale industrial plantations, the introduction of trees into existing agricultural systems, small-scale plantations by landowners, the establishment of woodlots on communal lands, and the rehabilitation of degraded areas through tree planting or assisted natural regeneration.[76]
Afforestation is the planting of trees where there was no previous tree coverage. There are three different types of afforestation that could have varying effects on the amount of
carbon dioxide that is taken from the atmosphere. The three kinds of afforestation are natural regeneration, commercial plantations, and
agroforestry.[77] Although afforestation can help reduce the
carbon emissions given off as a result of climate change, natural regeneration tends to be the most effective out of the three.[77] Natural regeneration typically concerns a wide variety of vegetation, making natural forest levels so plants can receive sunlight to undergo photosynthesis. Commercial plantations typically result in mass amounts of lumber, which if used for fuel, will release the stored CO2 back into the atmosphere. Agroforestry stores energy based on the size and type of plant, meaning that the effect will vary depending on what is planted.[77]
Wood harvesting and supply have reached around 550 million m3 per year, while the total increasing stock of European forests has more than quadrupled during the previous six decades. It now accounts for around 35 billion m3 of forest biomass.[78][79] Since the beginning of the 1990s, the amounts of wood and carbon stored in European forests have increased by 50% due to greater forest area and biomass stocks. Every year, European woods adsorb and store around 155 million tonnes CO2 equivalent. This is comparable to 10% of all other sectors' emissions in Europe.[78][80][81]
Forestry projects have faced increasing criticism of their integrity as offset or credit programs. A number of news stories in 2021–2023 have criticized nature-based carbon offsets, the REDD+ program, and certification organizations.[83][84][85] In one case it was estimated that around 90% of
rainforest offset credits of the
Verified Carbon Standard are likely to be "phantom credits".[86]
Tree planting projects in particular have been problematic. Critics point to a number of concerns. Trees reach maturity over a course of many decades. It is difficult to guarantee how long the forest will last. It may suffer clearing, burning, or mismanagement.[87][88] Some tree-planting projects introduce fast-growing invasive species. These end up damaging native forests and reducing biodiversity.[89][90][91] In response, some certification standards such as the Climate Community and Biodiversity Standard require multiple species plantings.[92] Tree planting in high latitude forests may have a net warming effect on the Earth's climate. This is because tree cover absorbs sunlight. This creates a warming effect that balances out their absorption of carbon dioxide.[93] Tree-planting projects can also cause conflicts with local communities and Indigenous people. This happens if the project displaces them or otherwise curtails their use of forest resources.[94][95][96]
REDD+ (or REDD-plus) is a framework to encourage
developing countries to reduce
emissions and enhance removals of
greenhouse gases through a variety of
forest management options, and to provide technical and financial support for these efforts. The acronym refers to "reducing emissions from
deforestation and forest degradation in developing countries, and the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks in developing countries".[97] REDD+ is a voluntary
climate change mitigation framework developed by the
United Nations Framework Convention on Climate Change (UNFCCC).[98] REDD originally referred to "reducing emissions from deforestation in developing countries", which was the title of the original document on REDD.[99] It was superseded by REDD+ in the Warsaw Framework on REDD-plus negotiations.Since 2000, various studies estimate that
land use change, including deforestation and
forest degradation, accounts for 12-29% of global
greenhouse gas emissions.[100][101][102] For this reason the inclusion of reducing emissions from land use change is considered essential to achieve the objectives of the UNFCCC.[103]
The Bali Action Plan
The Bali Action Plan was developed in December 2007 in Bali, Indonesia.[104][105] It is a direct result of The Kyoto Protocol of December 1997.[106][37] One of the key elements of The Bali Action Plan involves a concerted effort by the member countries of
The Kyoto Protocol to enact and create policy approaches that incentivize emissions reduction caused by deforestation and forest degradation in the developing world.[107] It emphasized the importance of sustainable forest management and conservation practices in mitigating climate change. This coupled with the increased attention to carbon emission stocks as a way to provide additional resource flows to the developing countries.[37]
The Billion Tree Campaign was launched in 2006 by the
United Nations Environment Programme (UNEP) as a response to the challenges of
global warming, as well as to a wider array of sustainability challenges, from water supply to
biodiversity loss.[108] Its initial target was the planting of one billion trees in 2007. Only one year later in 2008, the campaign's objective was raised to 7 billion trees—a target to be met by the climate change conference that was held in Copenhagen, Denmark in December 2009. Three months before the conference, the 7 billion planted trees mark had been surpassed. In December 2011, after more than 12 billion trees had been planted,
UNEP formally handed management of the program over to the not-for-profit
Plant-for-the-Planet initiative, based in Munich, Germany.[109]
Considered the largest reserve of biological diversity in the world, the
Amazon Basin is also the largest Brazilian biome, taking up almost half the nation's territory. The Amazon Basin corresponds to two fifths of
South America's territory. Its area of approximately seven million square kilometers covers the largest
hydrographic network on the planet, through which runs about one fifth of the
fresh water on the world's surface.
Deforestation in the Amazon rainforest is a major cause to climate change due to the decreasing number of trees available to capture increasing carbon dioxide levels in the atmosphere.[110]
The Amazon Fund is aimed at raising donations for non-reimbursable investments in efforts to prevent, monitor and combat deforestation, as well as to promote the preservation and sustainable use of forests in the
Amazon Biome, under the terms of Decree N.º 6,527, dated August 1, 2008.[111] The Norwegian Government, which is the largest donor to the fund, froze its funding in 2019 over deforestation concerns. Norway has tied the resumption of funding to proof of a reduction in deforestation.[112]
The Amazon Fund supports the following areas: management of public forests and protected areas, environmental control, monitoring and inspection, sustainable forest management, economic activities created with sustainable use of forests, ecological and economic zoning, territorial arrangement and agricultural regulation, preservation and sustainable use of biodiversity, and recovery of deforested areas. Besides those, the Amazon Fund may use up to 20% of its donations to support the development of systems to monitor and control deforestation in other Brazilian biomes and in biomes of other
tropical countries.[111]
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