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The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch as a result of human activity. The included extinctions span numerous families of bacteria, fungi, plants and animals, including mammals, birds, reptiles, amphibians, fish and invertebrates. With widespread degradation of highly biodiverse habitats 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, or no one has yet discovered their extinction. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates.
The Triassic–Jurassic (Tr-J) extinction event, often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.3 million years ago, and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, the entire class of conodonts and 23–34% of marine genera disappeared. On land, all archosauromorphs other than crocodylomorphs, pterosaurs, and dinosaurs went extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Some remaining non-mammalian therapsids and many of the large temnospondyl amphibians had gone extinct prior to the Jurassic as well. However, there is still much uncertainty regarding a connection between the Tr-J boundary and terrestrial vertebrates, due to a lack of terrestrial fossils from the Rhaetian (latest) stage of the Triassic. What was left fairly untouched were plants, dinosaurs, pterosaurs and mammals; this allowed the dinosaurs and pterosaurs to become the dominant land animals for the next 135 million years.
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. 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.
Habitat conservation is a management practice that seeks to conserve, protect and restore habitats and prevent species extinction, fragmentation or reduction in range. It is a priority of many groups that cannot be easily characterized in terms of any one ideology.
The Anthropocene is a proposed geological epoch dating from the commencement of significant human impact on Earth's geology and ecosystems, including, but not limited to, anthropogenic climate change.
Pleistocene megafauna is the set of large animals that lived on Earth during the Pleistocene epoch. Pleistocene megafauna became extinct during the Quaternary extinction event resulting in substantial changes to ecosystems globally. The role of humans in causing Pleistocene megafaunal extinctions is controversial.
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 study which represents the systematic study of 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 glacial and interglacial periods, which occur as alternate phases within an icehouse period and tend to last less than 1 million years. There are five known Icehouse periods in Earth's climate history, which are known as the Huronian, Cryogenian, Andean-Saharan, Late Paleozoic, and Late Cenozoic glaciations. The main factors involved in changes of the paleoclimate are believed to be the concentration of atmospheric carbon dioxide, changes in Earth's orbit, long-term changes in the solar constant, and oceanic and orogenic changes from tectonic plate dynamics. Greenhouse and icehouse periods have played key roles in the evolution of life on Earth by directly and indirectly forcing biotic adaptation and turnover at various spatial scales across time.
In climate science, a tipping point is a critical threshold that, when crossed, leads to large and often irreversible changes in the climate system. If tipping points are crossed, they are likely to have severe impacts on human society. Tipping behaviour is found across the climate system, in ecosystems, ice sheets, and the circulation of the ocean and atmosphere.
An ecological network is a representation of the biotic interactions in an ecosystem, in which species (nodes) are connected by pairwise interactions (links). These interactions can be trophic or symbiotic. Ecological networks are used to describe and compare the structures of real ecosystems, while network models are used to investigate the effects of network structure on properties such as ecosystem stability.
Planetary boundaries is a concept highlighting human-caused perturbations of Earth systems making them relevant in a way not accommodated by the environmental boundaries separating the three ages within the Holocene epoch. Crossing a planetary boundary comes at the risk of abrupt environmental change. The framework is based on scientific evidence that human actions, especially those of industrialized societies since the Industrial Revolution, have become the main driver of global environmental change. According to the framework, "transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-scale to planetary-scale systems."
The Sixth Extinction: An Unnatural History is a 2014 non-fiction 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 Non-Fiction for the book in 2015.
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, depending on whether the environmental degradation that leads to the loss is reversible through ecological restoration/ecological resilience or effectively permanent. The current global extinction, has resulted in a biodiversity crisis being driven by human activities which push beyond the planetary boundaries and so far has proven irreversible.
David P. Mindell is an American evolutionary biologist and author. He is currently a visiting scholar 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.
An ecosystem is considered collapsed when its unique biotic or abiotic features are lost from all previous occurrences. Ecosystem collapse causes ecological collapse within a system; essentially altering its stability, resilience, and diversity levels. It is, however, possible to reverse through careful restoration, and is thus not completely equivalent to species extinction. It occurs after a system has reached a so-called ecological 'tipping point', or crossed a critical threshold, and can no longer adequately respond to rapid changes in ecological conditions; either due to the suddenness or the scale of the changes.
A climate apocalypse generally denotes a predicted scenario involving the global collapse of human civilization and potential human extinction as either a direct or indirect result of anthropogenic climate change. Many academics and researchers posit that in actuality, unless a major course correction is imminently implemented, some or all of the Earth will be rendered uninhabitable as a result of extreme temperatures, severe weather events, an inability to grow crops, and an altered composition of the Earth's atmosphere.
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, 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 a professor in the Department of Biology at Stanford University, and holds the Paul S. and Billie Achilles Chair of Environmental Science. Her research interests include links between ecology and evolution, and understanding of the impacts of the Anthropocene.
The Princeton Science Library is a book series of popular science written by scientists known for their popular writings and originally published by Princeton University Press.
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.
