![22591477950_6a5d608a27_k.jpg](https://steemitimages.com/DQmU41L1g95MpoPGzJ4NAVXzNuf1iYEwNzub2YGHxFvfv8t/22591477950_6a5d608a27_k.jpg)
<center><a href="https://www.flickr.com/photos/lwpkommunikacio/22591477950">Picture By Lwp Kommunikáció - Flickr</a></center>

So, we're back in the new episode of "Pathological Aspect Of Extinction" where we try to explore and understand the extinction process along with any factors which could affect the rate of natural extinction. In the previous related article, I have listed some of the factors which could cause extinction process to proceed at an accelerated rate. 

> The factors can be divided into six:
>
> - Loss of habitat
> - Pollution
> - Introduced species
> - Overharvesting
> - Secondary extinction
> - Global changes

Habitat loss has been explained, and if any of you missed or are interested in reading it, you can click the link below, and you will be directed to the article. 

![Untitled.png](https://steemitimages.com/DQmSMJiUNHiG9nxetokiUa6F9v4pPPNCwWtHyAMpWgaGoDN/Untitled.png)

<center><a href="https://steemit.com/steemstem/@chloroform/pathological-aspect-of-extinction-3-habitat-loss">Pathological Aspect Of Extinction #3; Habitat Loss</a></center>

<div class="pull-right"><center>https://steemitimages.com/DQmXLKS7gRvQdgYheusUoygyHnmCpUUC9FN3ju3GDqPAC58/image.png<a href="https://commons.wikimedia.org/wiki/File:Holzstaemme.JPG">H.J. Sydow - Wikimedia</a></center></div>

As you all know, habitat loss is the primary factor which has caused the rate of extinction to exceed or became abnormally hasten compared to the typical progression of extinction that is expected of a living creature in an ecological system. In this article, we are going to explore other factors apart from habitat loss to make sense of this accelerated pathological extinction rate. I would touch three topics:

- Introduction of new species
- Secondary extinction
- Pollution

The rest would be discussed in the next article.

## Introduction Of New Species
<br>
<div class="pull-right"><center>https://steemitimages.com/DQmNZsgmnpxxDnGwuwSZjXLsmwDo7pzqmwruk6toQDDTXdQ/image.png<a href="https://commons.wikimedia.org/wiki/File:Moho_nobilis-Keulemans.jpg">John Gerrard Keulemans - Wikimedia</a></center></div>

If you have read some of my articles related to this topic, then you would know that species introduction has been a threat to the native population of a specific area. Polynesian, a population which has been colonizing eastern Pacific Islands in the past, has been responsible for causing more than 1000 extinction of endemic bird species. Obviously, birds are not the only creature which is affected by this transition; there are other species of exotic plants and animals which has been obliterated as the result of human's activities caused by this migration. Some of the bird's egg has been eaten by rats brought from the mainland, through the ship and some of the exotic plants have been destroyed by dairy animals which are introduced to satisfy an increased in food demands among the population.

The rat in the case example is a species which is introduced into the new ecological system unintentionally. There are a few other case examples which illustrated an unintentional spread of species in a different environment:

- Human's infection
- Tree snake in Guam

<div class="pull-left"><center>https://steemitimages.com/DQmazyL2n1V6SvR4MbHBHMutdWX3CbW7peq74uHeWMWBDrt/image.png<a href="https://commons.wikimedia.org/wiki/File:Guam_Rail_RWD.jpg">DickDaniels -
 Wikimedia</a></center></div>
 
In the past, a ship is the main method of introduction which is capable of bringing some species of hitchhiking creatures which might be capable of affecting the environment that they would be introduced in. Please note that not every introduction are harmful to the environment, but most of them are. Let's take a look at an example of an accidental introduction of tree snake in Guam. Before the introduction, there were 11 species of birds which are native to Guam:

- Micronesian starlings
- Guam flycatchers
- Guam rails
- Rufous fantails
- Bridled white-eyes
- Mariana crows
- Micronesian kingfishers
- White-throated ground doves
- Cardinal honeyeaters
- Mariana fruit doves
- Island swiftlets

<div class="pull-right"><center>https://steemitimages.com/DQmehzBdWSuqJz9UneYzt3t887gx5ATgKRipC1ETeX5zm77/image.png<a href="https://commons.wikimedia.org/wiki/File:Brown_tree_snake_(Boiga_irregularis)_(8387580552).jpg">Pavel Kirillove - WIkimedia</a></center></div>

The number of all the bird species which has been listed above has started to decline in the early 1960s due to the introductions of the brown tree snake from another region by a ship. It was obliterated region by region until only a small portion of them were thriving in northern Guam before they disappeared from that area as well. The snake has been hunting every one of the respective birds, consumed their eggs, threatened their natural habitat which resulted in their extinction. Of all the bird species mentioned above, only two to three of them were protected and raised in captivity. Some of the farmers have been reported to complain their poultry farm animals such as chickens have been declining due to this snake.

Snake has been only one example; there are other examples which illustrate the damage caused by an introduction of foreign species to the native's area especially in Guam.  Domestic cats which have been brought by humans when they were migrating to this part of northern America has demolished at least 30 species of island birds. Farm animals such as cows and goats have been feeding on a various type of native plant species which caused them to be demolished as well.

## Secondary Extinction
<br>
![13578843423_b822a78c68_o.png](https://steemitimages.com/DQmRDDfD9S1qRKw81gSG26r9sdXeaeGJzqN5RUiAyk7rZwy/13578843423_b822a78c68_o.png)
<center><a href="https://www.flickr.com/photos/121935927@N06/13578843423">Picture By Slyavula Education - Flickr</a></center>

I have mentioned countless times in my articles that when a species is obliterated their roles in the ecosystem would be replaced by a new population. The natural process of extinction has been taking place slowly, as any abrupt changes in the ecosystem could affect the entire biodiversity. This can be explained easily by using the food web analogy. If an animal is being obliterated in an ecosystem, their predators and prey would be affected by this changes. This changes would eventually affect the other species either in a good way or bad. If a living creature is obliterated as a consequence of an extinction event, this phenomenon is called as the secondary extinction. 

A study which has been carried out in the past has concluded that some species of parasites were dependent on the existence of specific kind of mammals and birds. If by any chance, one of the species of mammals extinct, then the parasite which inhabits the mammal will have a higher probability to disappear as well. This theory only applied to any kind of parasites which are found exclusively in a certain living creature. They can't thrive without specific hosts so they will be obliterated by the extinction event.

<div class="pull-right"><center>https://steemitimages.com/DQmauSsgK4TDgdEVN9TC9pzMdeEQKQkYkecBeco4R8jeZ3D/image.png<a href="https://commons.wikimedia.org/wiki/File:Drepanis_pacifica-Keulemans.jpg">John Gerrard Keulemans - Wikimedia</a></center></div>

To illustrate this event, let's take a look at how nectar-feeding bird species in the Hawaiian island are being obliterated as a consequence of extinction of nectar-producing plants. There are three species of nectar-feeding birds which inhabits the Hawaiian island before the event of human's migration:

- **Drepanis Pacifica** (Mamo)
- **Drepanis Funerea** (Black mamo)
- **Vestiaria Coccinea** (Iiwi)

Most of the bird species which has extinct in the Hawaiian island were caused by the destruction of their natural habitats and poaching. They were hunted for their feather which can be made into clothes but in the case of the three bird species above, they extinct or threatened to extinction due to the destruction of many nectar-producing native plants which are eaten by pigs, cows, and goats that were introduced to increase human's food sources. Mamo and black mamo have extinct while iiwi has extirpated in at least two islands as a result of the extinction of more than a quarter of the plant's population. 

Some of these plants have evolved to be pollinated by the three species of birds, but as the number of birds declined, the rate of pollination plummeted to the point of extinction. However, it is not known which of the species, either the plants or the birds which disappear first. Secondary extinction is quite complicated.

## Pollution 
<br>
![](https://steemitimages.com/DQmeqmvqpY9rzH6md9m1RqhVVG6XwQXFq17GRv1pZ6X2B1Q/image.png)
<center><a href="https://en.wikipedia.org/wiki/Pollution#/media/File:Litter.JPG">Picture By Nils Ally - Wikipedia</a></center>

Pollution can be considered as habitat destruction. However, the damage imposed is on a chemical level rather than physical. The damage imposed by pollutions are detrimental to animals, plants, humans and other living creature which existed. Nowadays, there are many habitats which have been polluted by chemical substances caused by human activities, such as agriculture, deforestation, and industrial activities. Global warming, any related poisoning has been a part of consequences which are caused by pollution, and if it is not controlled, it has the potential to wipe out a large portion of biodiversity.

<div class="pull-right"><center>https://steemitimages.com/DQmY4NQ29vHHKXxxCNH5yvw8DiZaEUHEmoAZzFXgVwm4aBo/image.png<a href="https://commons.wikimedia.org/wiki/File:US_Navy_050107-N-6074Y-198_The_coast_of_Sumatra,_Indonesia_in_the_southern_Aceh_region_reveals_her_beauty_in_spite_of_the_devastation_that_was_left_in_wake_of_the_Tsunami_that_struck_the_entire_region.jpg">U.S Navy - Wikimedia</a></center></div>

The coastal region of the ocean has been a habitat for various marine species. This is due to the fact that, most of the ocean is composed of deep, less-nutrient region which is incompatible for the development of marine life, so the coastal regions which are rich in nutrient were considered favourable places to live in. Industrial, agricultural and deforestation activities have been affecting the coastal area in different ways, but, we can agree that the majority if not all of them, are detrimental to the coastal region ecosystem. Waste products of a factory have been dumped in the flowing river, any chemical fertilizers which have been used in the agriculture were disposed in the river through runoff, and some of the soil would slowly be deposited in the river or the coastal area directly by the rain as a result of deforestation.

The pollution caused by human's activities typically affect freshwater and marine life compared to terrestrial lives. This is due to the fact that most of the chemical byproducts and detrimental agent were disposed of in the river, lake or even the ocean. Some of the polluted rivers might be supplying various plant species with poor-nutrient water which caused progressive vegetative changes as a result of the changing environment. 

![](https://steemitimages.com/DQmeEeNytQjSF9geJ9AbEuhZWrru7B2qj1rMp7g55Nm89h6/image.png)
<center><a href="https://commons.wikimedia.org/wiki/File:River_Nith_estuary.jpg">Picture By Doc Searls - Wikimedia</a></center>

Estuary, an area in which multiple rivers would combine and meet the sea, is one of the most polluted places in the world. The Northern Gulf of Mexico, for example, has been receiving water along with sediments and pollutants from the Mississippi River. Since salt waters of the ocean are much denser than the fresh water, the upper layer of the water found in the estuary contains a higher concentration of pollutants which includes phosphorus and nitrogen-based fertilizers. This will cause exponential growth of the ocean's phytoplankton which would also mean the number of phytoplankton which would die will increase. The decomposition process would use some oxygen in the water, and as the number of died phytoplankton increased, the level of oxygen in the water would decrease. This would affect the bottom dwellers such as crabs, shrimps and marine worms, which would die from suffocation due to insufficient oxygen resulting in an area which we would call the "dead zone".

Some of the pollutants have the reputation of affecting both marine lives and humans by inflicting different kind condition depending on the type of toxic organisms produced by the type of nutritional compartment of the polluted water. We could say that some diseases were imposed on marine lives and sometimes humans caused by the pollutants found in the water. 

I think most of you, generally, know that pollution can affect us in certain ways. Pollution is never good, and the effect is usually worldwide. Global warming is one of the consequences of pollution which is not discussed in this article, as the topic is quite extensive. I hope most of you get the idea, or at least some of it, how these three factors would affect biodiversity. I will be writing an article to describe the other two factors soon. Thank you for your attention and be sure to upvote if you like the content.

## References and further reading materials
<br>
- Stuart L. Pimm. Encyclopaedia Britannica. Conservation. Retrieved April 3, 2018, from https://www.britannica.com/science/conservation-ecology
- World Wildlife Fund. Pollution. Retrieved April 3, 2018, from https://www.worldwildlife.org/threats/pollution
- Wikipedia. Extinction. Retrieved April 3, 2018, from https://en.wikipedia.org/wiki/Extinction

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