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The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction, or is on the cusp of doing so. As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction; given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.
Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa.
The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as the environment's maximal load, which in population ecology corresponds to the population equilibrium, when the number of deaths in a population equals the number of births. Carrying capacity of the environment implies that the resources extraction is not above the rate of regeneration of the resources and the wastes generated are within the assimilating capacity of the environment. The effect of carrying capacity on population dynamics is modelled with a logistic function. Carrying capacity is applied to the maximum population an environment can support in ecology, agriculture and fisheries. The term carrying capacity has been applied to a few different processes in the past before finally being applied to population limits in the 1950s. The notion of carrying capacity for humans is covered by the notion of sustainable population.
In zoology, megafauna are large animals. The precise definition of the term varies widely, though a common threshold is approximately 45 kilograms (99 lb), with other thresholds as low as 10 kilograms (22 lb) or as high as 1,000 kilograms (2,200 lb). Large body size is generally associated with other traits, such as having a slow rate of reproduction and, in large herbivores, reduced or negligible adult mortality from being killed by predators.
The Anthropocene is a rejected proposal for a geological epoch following the Holocene, dating from the commencement of significant human impact on Earth up to the present day. This impact affects Earth's oceans, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen for example in biodiversity loss and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution, to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term. However, in 2024 the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) rejected the Anthropocene Epoch proposal for inclusion in the Geologic Time Scale.
Environmental degradation is the deterioration of the environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution. It is defined as any change or disturbance to the environment perceived to be deleterious or undesirable. The environmental degradation process amplifies the impact of environmental issues which leave lasting impacts on the environment.
An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own.
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years. It is further proposed that these warming events caused the Bond Cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials.
In landscape ecology, landscape connectivity is, broadly, "the degree to which the landscape facilitates or impedes movement among resource patches". Alternatively, connectivity may be a continuous property of the landscape and independent of patches and paths. Connectivity includes both structural connectivity and functional connectivity. Functional connectivity includes actual connectivity and potential connectivity in which movement paths are estimated using the life-history data.
Quaternary science is the subfield of geology which studies the Quaternary Period commonly known as the ice age. The Quaternary Period is a time period that started around 2.58 million years ago and continues today. This period is divided into two epochs – the Pleistocene Epoch and the Holocene Epoch. The aim of Quaternary science is to understand everything that happened during the Pleistocene Epoch and the Holocene Epoch to be able to acquire fundamental knowledge about Earth's environment, ecosystem, climate changes, etc. Quaternary science was first studied during the nineteenth century by Georges Cuvier, a French scientist. Most Quaternary scientists have studied the history of the Quaternary to predict future changes in climate.
Throughout Earth's climate history (Paleoclimate) its climate has fluctuated between two primary states: greenhouse and icehouse Earth. Both climate states last for millions of years and should not be confused with the much smaller glacial and interglacial periods, which occur as alternating phases within an icehouse period and tend to last less than one million years. There are five known icehouse periods in Earth's climate history, namely the Huronian, Cryogenian, Andean-Saharan, Late Paleozoic and Late Cenozoic glaciations.
In climate science, a tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system. If tipping points are crossed, they are likely to have severe impacts on human society and may accelerate global warming. Tipping behavior is found across the climate system, for example in ice sheets, mountain glaciers, circulation patterns in the ocean, in ecosystems, and the atmosphere. Examples of tipping points include thawing permafrost, which will release methane, a powerful greenhouse gas, or melting ice sheets and glaciers reducing Earth's albedo, which would warm the planet faster. Thawing permafrost is a threat multiplier because it holds roughly twice as much carbon as the amount currently circulating in the atmosphere.
Environmental issues are disruptions in the usual function of ecosystems. Further, these issues can be caused by humans or they can be natural. These issues are considered serious when the ecosystem cannot recover in the present situation, and catastrophic if the ecosystem is projected to certainly collapse.
The Sixth Extinction: An Unnatural History is a 2014 nonfiction book written by Elizabeth Kolbert and published by Henry Holt and Company. The book argues that the Earth is in the midst of a modern, man-made, sixth extinction. In the book, Kolbert chronicles previous mass extinction events, and compares them to the accelerated, widespread extinctions during our present time. She also describes specific species extinguished by humans, as well as the ecologies surrounding prehistoric and near-present extinction events. The author received the Pulitzer Prize for General Nonfiction for the book in 2015.
Biodiversity loss happens when plant or animal species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. Biodiversity loss means that there is a reduction in biological diversity in a given area. The decrease can be temporary or permanent. It is temporary if the damage that led to the loss is reversible in time, for example through ecological restoration. If this is not possible, then the decrease is permanent. The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far. These activities include habitat destruction and land use intensification. Further problem areas are air and water pollution, over-exploitation, invasive species and climate change.
David P. Mindell is an American evolutionary biologist and author. He is currently a senior researcher at the University of California, Berkeley, Museum of Vertebrate Zoology. Mindell's work is focused on the systematics, conservation and molecular evolution of birds, especially birds of prey. He is known for his 2006 book, The Evolving World in which he explained, for the general public, how evolution applies to everyday life.
Conservation paleobiology is a field of paleontology that applies the knowledge of the geological and paleoecological record to the conservation and restoration of biodiversity and ecosystem services. Despite the influence of paleontology on ecological sciences can be traced back at least at the 18th century, the current field has been established by the work of K.W. Flessa and G.P. Dietl in the first decade of the 21st century. The discipline utilizes paleontological and geological data to understand how biotas respond to climate and other natural and anthropogenic environmental change. These information are then used to address the challenges faced by modern conservation biology, like understanding the extinction risk of endangered species, providing baselines for restoration and modelling future scenarios for species range's contraction or expansion.
The term collapsology is a neologism used to designate the transdisciplinary study of the risks of collapse of industrial civilization. It is concerned with the general collapse of societies induced by climate change, as well as "scarcity of resources, vast extinctions, and natural disasters." Although the concept of civilizational or societal collapse had already existed for many years, collapsology focuses its attention on contemporary, industrial, and globalized societies.
Elizabeth Hadly is an academic and researcher working in biology, earth/environmental science, and paleoecology. As a professor in the Department of Biology at Stanford University, she holds the Paul S. and Billie Achilles Chair of Environmental Science and is the Head of the Faculty Senate. Her research interests include links between ecology and evolution, and understanding of the impacts of the Anthropocene.
Shahid Naeem is an ecologist and conservation biologist and is a Lenfest Distinguished professor and chair in the Department of Ecology, Evolution, and Environmental Biology at Columbia University. Naeem is the author of Biodiversity, Ecosystem Functioning, and Human Well-Being, and has published over 100 scientific articles.
References
- 1 2 3 Short Bio - Anthony D. Barnosky
- ↑ Hello, Governor: When California's governor enlisted the aid of two palaeoecologists, their careers took an unusual turn.
- ↑ Five Climate Tipping Points We've Already Seen, and One We're Hoping For
- ↑ Population growth is driving the migration crisis
- ↑ 10 Ways you can help stop the sixth mass extinction
- ↑ Barnosky, Anthony D.; Hadly, Elizabeth A.; Bascompte, Jordi; Berlow, Eric L.; Brown, James H.; Fortelius, Mikael; Getz, Wayne M.; Harte, John; Hastings, Alan; Marquet, Pablo A.; Martinez, Neo D.; Mooers, Arne; Roopnarine, Peter; Vermeij, Geerat; Williams, John W.; Gillespie, Rosemary; Kitzes, Justin; Marshall, Charles; Matzke, Nicholas; Mindell, David P.; Revilla, Eloy; Smith, Adam B. (2012). "Approaching a state shift in Earth's biosphere". Nature. 486 (7401): 52–58. Bibcode:2012Natur.486...52B. doi:10.1038/nature11018. hdl: 10261/55208 . ISSN 0028-0836. PMID 22678279. S2CID 4788164.
