The scientific community has been investigating the causes of climate change for decades. After thousands of studies, it came to a consensus, where it is "unequivocal that human influence has warmed the atmosphere, ocean and land since pre-industrial times." This consensus is supported by around 200 scientific organizations worldwide, The dominant role in this climate change has been played by the direct emissions of carbon dioxide from the burning of fossil fuels. Indirect CO2 emissions from land use change, and the emissions of methane, nitrous oxide and other greenhouse gases play major supporting roles.
A carbon sink is a natural or artificial carbon sequestration process that "removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". These sinks form an important part of the natural carbon cycle. An overarching term is carbon pool, which is all the places where carbon on Earth can be, i.e. the atmosphere, oceans, soil, florae, fossil fuel reservoirs and so forth. A carbon sink is a type of carbon pool that has the capability to take up more carbon from the atmosphere than it releases.
Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. About 31% of Earth's land surface is covered by forests at present. This is one-third less than the forest cover before the expansion of agriculture, with half of that loss occurring in the last century. Between 15 million to 18 million hectares of forest, an area the size of Bangladesh, are destroyed every year. On average 2,400 trees are cut down each minute. Estimates vary widely as to the extent of deforestation in the tropics. In 2019, nearly a third of the overall tree cover loss, or 3.8 million hectares, occurred within humid tropical primary forests. These are areas of mature rainforest that are especially important for biodiversity and carbon storage.
The Eocene is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name Eocene comes from the Ancient Greek Ἠώς and καινός and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.
In physical geography, tundra is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic tundra, alpine tundra, and Antarctic tundra.
The Amazon rainforest, also called Amazon jungle or Amazonia, is a moist broadleaf tropical rainforest in the Amazon biome that covers most of the Amazon basin of South America. This basin encompasses 7,000,000 km2 (2,700,000 sq mi), of which 6,000,000 km2 (2,300,000 sq mi) are covered by the rainforest. This region includes territory belonging to nine nations and 3,344 indigenous territories.
Afforestation is the establishment of a forest or stand of trees in an area where there was no recent tree cover. There are three types of afforestation: Natural regeneration, agroforestry and tree plantations. Afforestation has many benefits. In the context of climate change, afforestation can be helpful for climate change mitigation through the route of carbon sequestration. Afforestation can also improve the local climate through increased rainfall and by being a barrier against high winds. The additional trees can also prevent or reduce topsoil erosion, floods and landslides. Finally, additional trees can be a habitat for wildlife, and provide employment and wood products.
Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Climate change mitigation actions include conserving energy and replacing fossil fuels with clean energy sources. Secondary mitigation strategies include changes to land use and removing carbon dioxide (CO2) from the atmosphere. Current climate change mitigation policies are insufficient as they would still result in global warming of about 2.7 °C by 2100, significantly above the 2015 Paris Agreement's goal of limiting global warming to below 2 °C.
In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, canopy refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms. The communities that inhabit the canopy layer are thought to be involved in maintaining forest diversity, resilience, and functioning. Shade trees normally have a dense canopy that blocks light from lower growing plants.
Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in limiting climate change by reducing the amount of carbon dioxide in the atmosphere. There are two main types of carbon sequestration: biologic and geologic.
Soil carbon is the solid carbon stored in global soils. This includes both soil organic matter and inorganic carbon as carbonate minerals. It is vital to the soil capacity in our ecosystem. Soil carbon is a carbon sink in regard to the global carbon cycle, playing a role in biogeochemistry, climate change mitigation, and constructing global climate models. Microorganisms play an important role in breaking down carbon in the soil. Changes in their activity due to rising temperatures could possibly influence and even contribute to climate change. Human activities have caused a massive loss of soil organic carbon. For example, anthropogenic fires destroy the top layer of the soil, exposing soil to excessive oxidation.
Arctic methane emissions contribute to a rise in methane concentrations in the atmosphere. Whilst the Arctic region is one of many natural sources of the greenhouse gas methane, there is nowadays also a human component to this due to the effects of climate change. In the Arctic, the main human-influenced sources of methane are thawing permafrost, Arctic sea ice melting, clathrate breakdown and Greenland ice sheet melting. This methane release results in a positive climate change feedback, as methane is a powerful greenhouse gas. When permafrost thaws due to global warming, large amounts of organic material can become available for methanogenesis and may therefore be released as methane.
Carbon dioxide removal (CDR) is a process in which carbon dioxide is removed from the atmosphere by deliberate human activities and durably stored in geological, terrestrial, or ocean reservoirs, or in products. This process is also known as carbon removal, greenhouse gas removal or negative emissions. CDR is more and more often integrated into climate policy, as an element of climate change mitigation strategies. Achieving net zero emissions will require first and foremost deep and sustained cuts in emissions, and then—in addition—the use of CDR. In the future, CDR may be able to counterbalance emissions that are technically difficult to eliminate, such as some agricultural and industrial emissions.
The permafrost carbon cycle or Arctic carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0o C for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir, one which was often neglected in the initial research determining global terrestrial carbon reservoirs. Since the start of the 2000s, however, far more attention has been paid to the subject, with an enormous growth both in general attention and in the scientific research output.
Blue carbon is a concept within climate change mitigation that refers to "biologically driven carbon fluxes and storage in marine systems that are amenable to management". Most commonly, it refers to the role that tidal marshes, mangroves and seagrass meadows can play in carbon sequestration. These ecosystems can play an important role for climate change mitigation and ecosystem-based adaptation. However, when blue carbon ecosystems are degraded or lost, they release carbon back to the atmosphere, thereby adding to greenhouse gas emissions.
David John Beerling FLSW is the Director of the Leverhulme Centre for Climate change mitigation and Sorby Professor of Natural Sciences in the Department of Animal and Plant Sciences (APS) at the University of Sheffield, UK. He is also Editor-in-Chief of the Royal Society journal Biology Letters.
Deforestation is a primary contributor to climate change, and climate change affects the health of forests. Land use change, especially in the form of deforestation, is the second largest source of carbon dioxide emissions from human activities, after the burning of fossil fuels. Greenhouse gases are emitted from deforestation during the burning of forest biomass and decomposition of remaining plant material and soil carbon. Global models and national greenhouse gas inventories give similar results for deforestation emissions. As of 2019, deforestation is responsible for about 11% of global greenhouse gas emissions. Carbon emissions from tropical deforestation are accelerating.
The CO2 fertilization effect or carbon fertilization effect causes an increased rate of photosynthesis while limiting leaf transpiration in plants. Both processes result from increased levels of atmospheric carbon dioxide (CO2). The carbon fertilization effect varies depending on plant species, air and soil temperature, and availability of water and nutrients. Net primary productivity (NPP) might positively respond to the carbon fertilization effect. Although, evidence shows that enhanced rates of photosynthesis in plants due to CO2 fertilization do not directly enhance all plant growth, and thus carbon storage. The carbon fertilization effect has been reported to be the cause of 44% of gross primary productivity (GPP) increase since the 2000s. Earth System Models, Land System Models and Dynamic Global Vegetation Models are used to investigate and interpret vegetation trends related to increasing levels of atmospheric CO2. However, the ecosystem processes associated with the CO2 fertilization effect remain uncertain and therefore are challenging to model.
Yadvinder Singh Malhi is professor of Ecosystem Science at the University of Oxford and a Jackson Senior Research Fellow at Oriel College, Oxford.
This is an article of notable issues relating to the terrestrial environment of Earth in 2022. They relate to environmental events such as natural disasters, environmental sciences such as ecology and geoscience with a known relevance to contemporary influence of humanity on Earth, environmental law, conservation, environmentalism with major worldwide impact and environmental issues.
