Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence. We are currently in the midst of the Earth’s sixth mass extinction crisis. Harvard biologist E. O. Wilson estimated that 30,000 species per year are being driven to extinction. Compare this to the natural background rate of one extinction per million species per year. The current mass extinction is a crisis unparalleled in human history, the primary driver thereof being habitat loss and exploitation due to human overpopulation.
Human ecology is an interdisciplinary and transdisciplinary study of the relationship between humans and their natural, social, and built environments. The philosophy and study of human ecology has a diffuse history with advancements in ecology, geography, sociology, psychology, anthropology, zoology, epidemiology, public health, and home economics, among others.
Paul Ralph Ehrlich is an American biologist known for his predictions and warnings about the consequences of population growth, including famine and resource depletion. Ehrlich is the Bing Professor Emeritus of Population Studies of the Department of Biology of Stanford University.
William Ernest McKibben is an American environmentalist, author, and journalist who has written extensively on the impact of global warming. He is the Schumann Distinguished Scholar at Middlebury College and leader of the climate campaign group 350.org. He has authored a dozen books about the environment, including his first, The End of Nature (1989), about climate change, and Falter: Has the Human Game Begun to Play Itself Out? (2019), about the state of the environmental challenges facing humanity and future prospects.
The Anthropocene is a now rejected proposal for the name of a geological epoch that would follow the Holocene, dating from the commencement of significant human impact on Earth up to the present day. It was rejected in 2024 by the International Commission on Stratigraphy in terms of being a defined geologic period. The impacts of humans affect 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.
Space and survival is the idea that the long-term survival of the human species and technological civilization requires the building of a spacefaring civilization that utilizes the resources of outer space, and that not doing this might lead to human extinction. A related observation is that the window of opportunity for doing this may be limited due to the decreasing amount of surplus resources that will be available over time as a result of an ever-growing population.
Spiritual ecology is an emerging field in religion, conservation, and academia that proposes that there is a spiritual facet to all issues related to conservation, environmentalism, and earth stewardship. Proponents of spiritual ecology assert a need for contemporary nature conservation work to include spiritual elements and for contemporary religion and spirituality to include awareness of and engagement in ecological issues.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
Doomers are people who are extremely pessimistic or fatalistic about global problems such as overpopulation, peak oil, climate change, ecological overshoot, pollution, nuclear weapons, and runaway artificial intelligence. The term, and its associated term doomerism, arose primarily on social media. Some doomers assert that there is a possibility these problems will bring about human extinction.
Religion and environmentalism is an emerging interdisciplinary subfield in the academic disciplines of religious studies, religious ethics, the sociology of religion, and theology amongst others, with environmentalism and ecological principles as a primary focus.
Global biodiversity is the measure of biodiversity on planet Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 2 million to 1 trillion, but most estimates are around 11 million species or fewer. About 1.74 million species were databased as of 2018, and over 80 percent have not yet been described. The total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 x 1037, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).
The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by its extreme size bias towards large animals, and widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.
A global catastrophic risk or a doomsday scenario is a hypothetical event that could damage human well-being on a global scale, even endangering or destroying modern civilization. An event that could cause human extinction or permanently and drastically curtail humanity's existence or potential is known as an "existential risk".
In environmental science, a population "overshoots" its local carrying capacity — the capacity of the biome to feed and sustain that population — when that population has not only begun to outstrip its food supply in excess of regeneration, but actually shot past that point, setting up a potentially catastrophic crash of that feeder population once its food populations have been consumed completely. Overshoot can apply to human overpopulation as well as other animal populations: any life-form that consumes others to sustain itself.
Andrew C. Revkin is an American science and environmental journalist, webcaster, author and educator. He has written on a wide range of subjects including destruction of the Amazon rainforest, the 2004 Asian tsunami, sustainable development, climate change, and the changing environment around the North Pole. From 2019 to 2023 he directed the Initiative on Communication and Sustainability at The Earth Institute of Columbia University. While at Columbia, he launched a video webcast, Sustain What, that seeks solutions to tangled environmental and societal challenges through dialogue. In 2023, the webcast integrated with his Substack dispatch of the same name.
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.
Paul Schultz Martin was an American geoscientist at the University of Arizona who developed the theory that the Pleistocene extinction of large mammals worldwide was caused by overhunting by humans. Martin's work bridged the fields of ecology, anthropology, geosciences, and paleontology.
Ecomodernism is an environmental philosophy which argues that technological development can protect nature and improve human wellbeing through eco-economic decoupling, i.e., by separating economic growth from environmental impacts.
Jacquelyn Gill is a paleoecologist and assistant professor of climate science at the University of Maine. She has worked on such as the relationship between megafauna and vegetation in the Pleistocene, and the sediment cores of Jamaica. Gill is also a science communicator on climate change.
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.
