Local extinction

Local extinction occurs when there is environmental changes that somehow reduces a species ability to survive in the particular habitat. One of the biggest causes is habitat destruction which is essentially occurs when natural ecosystems has been negatively changed for agriculture, urban development, and many other such human activities. When there is habitats that are being destroyed or changed, you would typically see specie's populations to slowly decline or diminish until they completely disappear in that specific region. This can thus lead to habitat fragmentation which has contribute to local extinction by dividing continuous and connected habitats into more smaller and isolated patches. the reduction in size and isolation has negatively impacted the species such as lowering population size, slow down movements among populations and decrease the overall genetic diversity which can unfortunately increase the risk of a major population collapse (Fahrig, 2003).Another crucial component that has contributed to local exploitation is the overexploitation of species and the rapid environmental changes driven by human activity and development. Essentially Overexploitation has occur when species are being harvested and used at a such fast rate then the specie can reproduce and recover. Such human activities like overfishing and. hunting can be responsible in reducing a species population size and thus make the species more vulnerable to extinction in specific regions. Also, climate change has been increasingly on the rise in impacting a species survival as changes in temperature, precipitation patterns, and climate abnormalities and severe weather like hurricanes and tornados can impact ecosystems and even disrupt the environmental conditions that the species depend on survival like food and water sources. When all of these pressures and external factor come to play with also the habitat loss and habitat fragmentation, we can see specie's population to struggle to adapt to these rapidly changing/evolving environments. Smaller and isolated populations are often have less resistance to these environmental stresses and disturbance and have less ability to recover from such disturbances. Thus these ecological pressures can really impact the chance of survival of the species population and increase the likelihood that species populations will disappear from certain regions and this has contribute to signs and patterns of local extinction(Rodolfo et al.,2014). == Metapopulation dynamics ==

Metapopulation dynamics is an crucial component in really understanding how species survive across many fragmented habitats and also how local extinction occurs. A metapopulation basically refers to an group of spatially or fragmented separated populations of the same species that live in different habitat patches but are interconnected due to migration and dispersal. Species survival across different landscapes often depend on the specific balance between the local extinction and recolonization events, where populations that vanish in one particular habitat patch can be re-established or reintegrated through individuals migrating from nearby populations(Hansik,1998). Also, Harrison 1991 also explains that habitat fragmentation can create connected networks that smaller populations that interact with each other, and the long term persistence of the species depend on the movement of the species between thiase habitat patches. However, if Dispersal between these patches are reduced or there is isolation among the habitat patches, the odds or recolonization becomes very less likely and thus the chances of permeant local extinction increases(Harrison,1991) . Now the reason why understanding metapopulation dynamics is important because it helps us explain why there are some species that are able to recover after a local population losses or collapse while the other aren't so lucky and they decline when their habitat connectivity is disrupted. == Extinction debt ==

Essentially extinction debt basically refers to the slow loss of species that follow some habitat destruction or an environmental disturbance. There are some species populations that some how continue to exist for some amount of time even though the long term conditions for their survival is gone. In these specific situations, some species may be available in a habitat for years and decades once there is degradation in the environment, but the ecological changes within the environment have already reduced their odds for an specie's long term stay(Tilman et al.,1994).extinction debt also highlights how biodiversity loss can happen eventually rather than sudden after a specific environmental change. Research also shows that habitat fragmentation and environmental degradation would lead to negative ecological conditions that would slowly reduce and population stability and their reproductive success rate which would lead to indirect population collapse of the species in that habitat which would eventually lead to the species disappearance from that region even though they survived the environmental disturbance(Jackson,2010). extinction debt is one of biggest factors for local extinction for an specie in a habitat patch. Extinction debt is very important because it shows how that current species population might not reflect the long term impacts of previous environmental degradation. Conservation strategies take account of historical habitat loss and how the ecosystems changes when evaluation future extinction risks and losses. == Extinction risk ==

Extinction risk is essentially the probability that a species will disappear from a specific region based on ecological, biological and other environmental factors. Many Scientist will analyze many characteristics of the species populations to which to estimate among which species is the most vulnerable to extinction and therefore need the most attention. These analysis take account of variables such as population size, geographic range, availability in the habitat and the most unique of all the biological traits of a species. Research has shown that for specific biological characteristic have an strong impact to the odds of extinction risk. One such example that supports this is species with a small geographic range, slow life histories or expectancies and even high tropic levels have the greatest vulnerability to extinction risk compared to species with better/wider distributions and faster reproductive rates. Studies also show by comparing many different animal groups that have shown that these such biological abilities/traits can explain a large ratio of the different chances of extinction risk among species(Purvis et al., 2000). Also there are environmental pressures such as habitat loss, habitat fragmentation and negative human interactions that have directly related to increase local extinction risk for many species around the world. We see ecological studies have shown that when there is external pressures that interact with the species biological characteristics, there are many populations that would decline at such a rapid rate and become less capable for recovery. This leads scientist to use predictive models and comparative analyses to identify which species have the highest extinction risk and are the most likely to experience future population falls and local extinction(Cardillo et al.,2005). Essentially extinction risk is important as it allows for researchers and conservation authorities to prioritize species that need the most protection from local extinction. By identify the species with the highest extinction risk, there can be better conservation strategies that can be centered in protecting many habitats, stabilizing populations and slowing down the threats that lead to extinction. == 6th mass extinction and biodiversity loss: ==

The Idea of a 6th mass extinction refers to the overall global decline biodiversity in this current century and it is driven by extensive human activities such as deforestation and pollution. Throughout history there were 5 major mass extinction events, one such most notably is the asteroid that killed the dinosaurs, each lead a rapid loss of a large portion of species in a short time period. However, scientist today argue that earth is entering a so called 6th mass extinction event which was caused by the negative human impact toward all the ecosystems(Barnosky,et al.,2011). Such. human influences include habitat destruction and fragmentation, climate change, pollution and the overexploitation of our natural resources all of such would forever change our natural environments and threaten local extinction to a lot of species. Also recent ecological studies have shown that documented widespread population declines across a lot of species most notably among vertebrates species. It was shown that numerous vertebrate populations have experience significant fall of population size and geographic range which support the significant biodiversity loss across many ecosystems. These declines have often came from negative human activities that damage the habitats and the ecosystems. Now when these species disappear from these specific regions and habitats, it can contribute to a more global biodiversity decline which would eventually lead to the complete local extinction for the species. As a result of this, many scientist are increasingly viewing local population loss as an indicator of the global biodiversity problem(Ceballos et al., 2017) ==Discussion==

Glaciation is one factor that leads to local extinction. This was the case during the Pleistocene glaciation event in North America. During this period, most of the native North American species of earthworm were killed in places covered by glaciation. This left them open for colonization by European earthworms brought over in soil from Europe. Species naturally become extinct from islands over time; this can be either local extinction if the species also occurs elsewhere, or in cases of island endemism, outright extinction. The number of species an island can support is limited by its geographical size. Because many islands were relatively recently formed due to climate change at the end of the Pleistocene when the sea level rose, and these islands most likely had the same complement of species as found on the mainland, counting the species that still survive at present on a statistically large enough number of islands will give the parameters with which certain groups of species such as plants or birds will become less biodiverse on a given island over a given period of time, depending on its size. The same calculations can also be applied to determine when species will disappear from nature parks ('islands' in many senses), mountain tops and mesas (see sky islands), forest remnants or other such distributional patches. This research also demonstrates that certain species are more prone to extinction than others, a species has an intrinsic extinction-ability (incidence function). Some species exploit or require transient or disturbed habitats, such as vernal pools, a human gut, or burnt woodland after forest fires, and are characterised by highly fluctuating population numbers and shifting distributional patterns. Many natural ecosystems cycle through a standard succession, pioneer species disappear from a region as the ecosystem matures and reaches a climax community. A local extinction can be useful for research: in the case of the bay checkerspot butterfly, scientists, including Paul R. Ehrlich, chose not to intervene as a population disappeared from an area in order to study the process. Many crocodilian species have experienced localized extinction, particularly the saltwater crocodile (Crocodylus porosus), which has been extirpated from Vietnam, Thailand, Java and many other areas. Major environmental events, such as volcanic eruptions, may lead to large numbers of local extinctions. Heat waves can lead to local extinction. In New Zealand, during the summer of 2017–2018, sea surface temperatures around parts of South Island exceeded , which was well above normal. Air temperatures were also high, exceeding . These high temperatures, coupled with small wave height, led to the local extinction of bull kelp (Durvillaea spp.) from Pile Bay. Lagoa Santa, a lake in Lagoa Santa, Brazil, has lost almost 70% of the local fish species over the last 150 years. These include Acestrorhynchus lacustris, Astyanax fasciatus, and Characidium zebra. This could be caused by the introduction of non-native species, such as Tilapia rendalli, into the lagoon, changes in water level and organic pollution. Local extinctions can be reversed, in some cases artificially. Wolves are a species that have been reintroduced into parts of their historical range. This has happened with red wolves (Canis rufus) in the United States in the late 1980s and also grey wolves in Yellowstone National Park in the mid-1990s. There have been talks of reintroducing wolves in Scotland, Japan, and Mexico. ==Subpopulations and stocks==

When the local population of a certain species disappears from a certain geographical delimitation, whether fish in a drying pond or an entire ocean, it can be said to be extirpated or locally extinct in that pond or ocean. A particular total world population can be more or less arbitrarily divided into 'stocks' or 'subpopulations', defined by political or other geographical delimitations. For example, the Cetacean Specialist Group of the International Union for Conservation of Nature (IUCN) has assessed the conservation status of the Black Sea stock of harbour porpoise (Phocoena phocoena) that touches six countries, and COSEWIC, which only assesses the conservation status of wildlife in Canada, even assesses Canadian species that occur in the United States or other countries. While the IUCN mostly only assesses the global conservation status of species or subspecies, in some older cases it also assessed the risks to certain stocks and populations, in some cases these populations may be genetically distinct. In all, 119 stocks or subpopulations across 69 species had been assessed by the IUCN in 2006. If a local stock or population becomes extinct, the species as a whole has not become extinct, but extirpated from that local area. Examples of stocks and subdivisions of world populations assessed separately by the IUCN for their conservation status are: • Marsh deer (three populations assessed) • Blue whale, North Pacific and North Atlantic stocks • Bowhead whale, Balaena mysticetus (five populations assessed, from critically endangered to LR/cd) • Lake sturgeon, Acipenser fulvescens, Mississippi & Missouri Basins population assessed as vulnerable • Wild common carp, Cyprinus carpio (distribution in the River Danube) • Black-flanked rock-wallaby Petrogale lateralis (MacDonnell Ranges population and Western Kimberly population) The IUCN also lists countries where assessed species, subspecies or geographic populations are found, and from which countries they have been extirpated or reintroduced. ==See also==