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 or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of varient at the genetic,species,and ecosystem levels. diversity is not distributed evenly on Earth;it is usually 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 100 of Earth's terrestrial face and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa. Marine coastal biodiversity is highest globally speaking in the Western indian ocean steered mainly by the highest surface temper In all oceans across the planet,marine species varsity peaks in the mid-latitudinal zones. Terrestrial species threatened with mass extinction can be observed in exceptionally dense regional biodiversity hotspots,with high levels of species endemism under threat. There are 36 such hotspot regions which require the world's attention in order to secure union biodiversity.
In zoology,megafauna are large animals. The most common thresholds to be a megafauna are weighing over 45 kg (99 lb) or weighing over 1,000 kg (2,200 lb). The first occurrence of the term was in 1876. After the Cretaceous–Paleogene extinction event wiped out all non-avian dinosaurs,mammals and other vertebrates experienced an expansion in size. Millions of years of evolution led to gigantism on every major land mass. During the Quaternary extinction event,many species of megafauna went extinct as part of a slowly progressing extinction wave that affected ecosystems worldwide.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species,their habitats,and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences,and the practice of natural resource management.
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.
An ecological or environmental crisis occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
An apex predator,also known as a top predator,is a predator at the top of a food chain,without natural predators of its own.
Naturalisation is the ecological phenomenon through which a species,taxon,or population of exotic origin integrates into a given ecosystem,becoming capable of reproducing and growing in it,and proceeds to disseminate spontaneously. In some instances,the presence of a species in a given ecosystem is so ancient that it cannot be presupposed whether it is native or introduced.
Charismatic megafauna are animal species that are large—in the relevant category that they represent—with symbolic value or widespread popular appeal,and are often used by environmental activists to gain public support for environmentalist goals. In this definition,animals such as penguins or bald eagles can be considered megafauna because they are among the largest animals within the local animal community,and they disproportionately affect their environment. The vast majority of charismatic megafauna species are threatened and endangered by overhunting,poaching,black market trade,climate change,habitat destruction,invasive species,and many more causes. In a 2018 study,the top twenty most popular charismatic megafauna were found to be:the tiger,lion,elephant,giraffe,leopard,giant panda,cheetah,polar bear,wolf,gorilla,chimpanzee,zebra,hippopotamus,great white shark,crocodile,dolphin,rhinoceros,brown bear,koala and blue whale.
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 numerous extinctions of predominantly megafaunal animal species,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 the 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.
There is an ongoing decline in plant biodiversity,just like there is ongoing biodiversity loss for many other life forms. One of the causes for this decline is climate change. Environmental conditions play a key role in defining the function and geographic distributions of plants. Therefore,when environmental conditions change,this can result in changes to biodiversity. The effects of climate change on plant biodiversity can be predicted by using various models,for example bioclimatic models.
Rewilding is a form of ecological restoration aimed at increasing biodiversity and restoring natural processes. It differs from other forms of ecological restoration in that rewilding aspires to reduce human influence on ecosystems. It is also distinct from other forms of restoration in that,while it places emphasis on recovering geographically specific sets of ecological interactions and functions that would have maintained ecosystems prior to human influence,rewilding is open to novel or emerging ecosystems which encompass new species and new interactions.
In ecology,the term productivity refers to the rate of generation of biomass in an ecosystem,usually expressed in units of mass per volume per unit of time,such as grams per square metre per day. The unit of mass can relate to dry matter or to the mass of generated carbon. The productivity of autotrophs,such as plants,is called primary productivity,while the productivity of heterotrophs,such as animals,is called secondary productivity.
Equus semplicatus was a Pleistocene species of New World stilt-legged horse,and considered the type species for the stilt legged horses,one of three lineages of equids within the Americas,the other two being hippidionid and caballine horses. Now extinct,Equus semiplicatus once inhabited North America.
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.
Sandra Myrna DíazForMemRS is an Argentine ecologist and professor of ecology at the National University of Córdoba,who has been awarded with the Linnean Medal for her scientific work. She studies the functional traits of plants and investigates how plants impact the ecosystem.
The wood-pasture hypothesis is a scientific hypothesis positing that open and semi-open pastures and wood-pastures formed the predominant type of landscape in post-glacial temperate Europe,rather than the common belief of primeval forests. The hypothesis proposes that such a landscape would be formed and maintained by large wild herbivores. Although others,including landscape ecologist Oliver Rackham,had previously expressed similar ideas,it was the Dutch researcher Frans Vera,who,in his 2000 book Grazing Ecology and Forest History,first developed a comprehensive framework for such ideas and formulated them into a theorem. Vera's proposals,although highly controversial,came at a time when the role grazers played in woodlands was increasingly being reconsidered,and are credited for ushering in a period of increased reassessment and interdisciplinary research in European conservation theory and practice. Although Vera largely focused his research on the European situation,his findings could also be applied to other temperate ecological regions worldwide,especially the broadleaved ones.
Richard Simon Ostfeld is a Distinguished Senior Scientist at the Cary Institute of Ecosystem Studies in Millbrook,New York. He is best known for his work on the ecology of Lyme disease,which he began studying while monitoring the abundance of small mammals in the forests of Cary Institute property in the early 1990s.
Megaherbivores are large herbivores that can exceed 1,000 kg (2,200 lb) in weight. They first appeared 300 million years ago in the early Permian,in the form of synapsids. They were then replaced by megaherbivorous dinosaurs that went extinct in the Cretaceous-Paleogene extinction event. After this period,small mammalian species evolved into large herbivores in the Paleogene. During the Quaternary Extinction Event,megaherbivores disappeared on most continents on Earth. Recent megaherbivores include elephants,rhinos,hippos,and giraffes. There are nine extant species of terrestrial megaherbivores living in Africa and Asia. The African bush elephant is the largest extant species.
