A species is said to be extinct with the death of the last surviving member of the species. However, a species may become functionally extinct even if a few of its members are alive but are not able to reproduce due to various reasons such as age, disease, genetic damage etc. , and are therefore unable to sustain the existence of the species any further. A species can also be functionally extinct when a specific population is maintained in an artificial environment such as a zoo with no scope or hope for future reintroduction into the wild or its natural habitat.
In the course of evolution, it happens many a type that a species that have evolved a ancestor still survives and procreates while the ancestor from which it descended becomes extinct. Such type of extinctions in which the parent species no longer exists but the evolved daughter species lives on is known as pseudo extinction. Again, when a species no longer exists in a specified geographical location it may be said to be locally extinct although it could exist in another geographical location. Local extinction is also termed as extirpation.
For the purpose of this paper, the term extinction will broadly encompass all the types of extinction and will generally refer to the end of existence of a particular species. When a wide range of species are wiped off the face of the earth it is known as mass extinction. Scientists estimate that there have been at least five mass extinctions in the history of the earth due natural causes such as sudden drastic climatic changes or meteor hits. The Cretaceous-Tertiary extinction event which occurred almost 65 million years ago was responsible for the extinction of the dinosaurs.
Many scientists now believe that the earth is now in the initial throes of another mass extinction, this time man made, and has termed this human-made mass extinction the Halocene Extinction event. Causes Changes are inevitable, more so when we view it from the perspective the earth as a whole and the accompanying natural climatic, geographic and geological processes. Surviving changes has been an acceptable fact of life, and the maxim ‘Survival of the fittest’ has held true throughout the different ages.
Those species that have not been able to adapt and evolve with changing conditions have not been able to survive. This has been the natural course of things. “Over geological time, all species have a finite span of existence. Species extinction is therefore a natural process which occurs without the intervention of man. ” (Understanding Biodiversity) The advent of human beings has added a new and alarming dimension to species extinction – man-made factors that could lead to a process of extinction much wider in range and much expedited in the geographical scale of time.
When human beings dispersed widely over the earth they engaged in activities detrimental to the existence and survival of a wide variety of species. “…it is beyond question that extinctions caused directly or indirectly by man are occurring at a rate which far exceeds any reasonable estimates of background extinction rates, and which, to the extent that it is correlated with habitat perturbation, must be increasing. ” (Understanding Biodiversity) Human activities that lead to extinction can be divided into two categories: direct and indirect.
Direct activities are those activities that affect the concerned species directly. These include hunting, collecting and persecution. Indirect activities that could lead to extinction are those which do not affect the species directly but lead to the destruction or modification of their habitat. Agricultural activities, industrial activities and developmental activities can be included in the category of such activities. Hunting and trophy collection has been the direct cause of extinction of many species. Nature has a way of replenishing depleted resources within its scheme of things.
Had human beings resorted to hunting only for the sake of survival, and exploited the available resources cautiously and reasonably, there could have been no cause for alarm. But wanton overexploitation of natural flora and fauna resources has been the root cause of extinction o many species. “A species that faces overexploitation is one that may become severely endangered or even extinct due to the rate in which the species is being used. Unrestricted whaling during the 20th century is an example of overexploitation, and the whaling industry brought many species of whales to extremely low population sizes. (Causes of Endangerment)
Hunting and collection of species are resorted to for many reasons – very often superstitious and false. The horn of the rhinoceros is supposed to have aphrodisiac qualities, the rhinoceros was therefore mercilessly killed for their horns; many plants are supposed to have medicinal or magical powers, these are therefore collected from the wild without any thought of growing or cultivating them. In other cases certain species are persecuted because of the harm that they cause to crops, food materials or other human interests.
There are then culled or killed with the use of pesticides and other mass elimination methods leading to their extinction. Indirect effect of human activities Destruction or modification of habitat is one of the main reasons of extinction. There are a wide range of human activities that indirectly impact on the habitat of many species. Clearing of forest areas for agriculture has been a major cause of loss of habitat since human beings took to cultivation. There are also many overtly harmful conventional agricultural practices such as shifting cultivation that causes meaningless destruction to habitats of species.
Agriculture is a leading cause, with about 45 percent of the total land area in the U. S. used for farming. Besides causing the direct replacement of natural habitat with fields, agricultural activity also results in soil erosion, pollution from pesticides and fertilizers, and runoff into aquatic habitats. Agriculture has impacted forest, prairie, and wetland habitats in particular. ”(Factors that contribute to Species Endangerment) Growth of towns and cities, setting up of industries, building up of dams, grazing of animals, mining, are all instrumental in harming habitat in one way or the other.
Industries not only need large areas, their effluents also cause water and air pollution, mining destroys vegetation and soil, dams destroy aquatic habitats, and grazing not only harms the habitat directly but also impacts the species that competes with the livestock in food. One of the most prestine areas on the earth the continent of Australia has been ravaged by such activities: “Since the first European settlers arrived in 1788, Australia has lost 10 species of marsupials, including three bandicoots, the thylacine or Tasmanian tiger, and several wallabies and potoroos.
This represents a quarter of the world’s mammal extinctions during this period. ” (Szabo, 1995) Land use patterns of human beings often cause fragmentation of species habitat. Fragmentation of habitat paves the way for extinction as the species are not able to disperse from one fragment to another and are more exposed to the negative affects of the ‘edges’ of the habitat, such as exposure to predators and human-generated vulnerabilities. Invasive Species The phenomenon of invasive species leading to the extinction of weaker local species has also been largely a contribution of human beings.
In many cases the invasive species have been deliberately introduced, while in other cases such introduction has been inadvertent in nature. Invasive species lead to the extinction of native species by competing with them for food and other resources, by preying on the native species or by subsisting on the native species as parasites. The Australian marsupial is such an example. Early settlers released cats in Australia. Australia has a population of more than 12 million cats now.
The European red foxes were introduced for sport in the middle of the 19th Century. …feral cats prey on 64 species of native mammals, including possums, bandicoots and the swamp wallabies, and estimates that each cat can kill up to a thousand times a year. ” (Paton, 1995) Global Warming The term global warming refers to the gradual rise in temperature across the earth. A major share of the energy requirement of the earth is derived from the burning of fossil fuels. When fossil fuels are burnt, carbon dioxide is released into the atmosphere resulting in what is known as the ‘greenhouse’ effect and rise in temperatures all over the earth.
Gutierrez (2007) reports that “by the year 2100, global warming likely will cause the extinction of numerous species by eliminating the climate zones in which they are able to live…” Global warming could wreck havoc with the habitats of different species pushing them towards certain extinction. Loss of forest cover and global warming acts in a vicious cycle. Los of forest cover contributes to global warming and global warming in turn will contribute to loss of forests. “As the global climate warms up, patterns of rainfall will change; and ‘normal’ temperature patterns will be disrupted.
The expected rate of global warming and sea-level rise will be too fast to allow most forests to be able to adapt quickly enough to survive. ” (Web of Creation, 2000) Protecting Species from Extinction It is very evident that human beings are primarily at the root of the problem of a wide variety of flora and fauna species facing extinction. It therefore falls on human beings to take adequate measures to protect these species from extinction. Conservation of endangered species is a cure rather than a remedy. It will however be the remedial measures that will be able to say the situation.
All governments should frame necessary laws and regulations against human activities such as hunting, collection and persecution. Agricultural practices, industrial and urban developments and land use patterns should be regulated in such a way that the habitats of flora and fauna are not harmed or modifies. Deliberate efforts should be made to curb global warming by the use of non-conventional sources of energy. Different species are interdependent in the ecosystem. The loss of biodiversity is a certain path to extinction of the species of homo sapiens also.