Disruptions in Ecosystems

Definition of Ecosystem

For starters, let's take a look at the definition of an ecosystem.

Ecosystems take into account both the biotic (living) and abiotic (non-living) components of the environment. In the ecological level of organization, ecosystems are larger than communities, which consist of only the biotic components of the environment, and smaller than the biome.

Examples of ecosystems include specific areas, such as the Amazon rainforest, Bornean peat swamps, the paperbark swamps of northern Australia, and the Serengeti tropical savanna. Over periods of time, ecosystems experience changes due to disruptions.

Definition of Disruptions in Ecosystems

Now that we know what an ecosystem is, let's look at the definition of disruption.

These events may be biotic or abiotic, as well as natural or anthropogenic, in origin, and may change ecosystems through increased organism mortality or drastic changes to the environment (or both).

Natural Disruptions to Ecosystems

There are several natural events that can disrupt ecosystems, including the following:

• Asteroid/meteor impacts

• Flooding

• Wildfires

• Volcanic eruptions

So, let's talk about each of these in detail!

Asteroid/meteor impacts

Perhaps the most extreme, catastrophic, and least common form of natural ecosystem disruption, asteroid impacts cause widespread mortality and changes to the environment. In prehistory, asteroid impacts have wiped out numerous species, resulting in mass extinction events, such as the Chicxulub asteroid impact that marked the end of the Cretaceous Period and likely resulted in the extinction of non-avian dinosaurs.

Flooding

Flooding is another example of a natural ecosystem disruption event. Large floods can cause excess mortality through drowning (of both animals and plants) and change the physical environment by washing away soil. Many species have adapted to annual flooding, particularly species that live on flood plains.

Wildfires

While many wildfires in modern times are anthropogenic in origin (through arson, negligence, and technological failure), naturally occurring wildfires (caused by drought, lightning strikes, etc.) are still a major cause of natural ecosystem disruption.

In addition to the obvious mortality resulting from wildfires, they also affect the physical environment by increasing the erosion of soil due to the death of large amounts of vegetation.

Like floods, wildfires play an important, positive role in the environment as well. Wildfires aid in the removal of decaying or dying plants, while providing nutrient rich soil for the next generation.

Volcanic Eruptions

Like asteroid impacts, volcanic eruptions can be quite catastrophic and cause sudden, drastic changes to the environment.

Volcanic eruptions and their subsequent pyroclastic flows wipe out most living organisms within the surrounding area and cover it with a thick layer of ash, leaving behind a large ash field.

Anthropogenic (human-caused) Disruptions to Ecosystems

Humans cause disruptions to ecosystems in numerous ways, most of them negative. Many of these disruptions are related to and fuel each other (e.g., climate change can result in habitat destruction). The following are just a few examples of anthropogenic ecosystem disruptions.

Climate Change

Since the start of the Industrial Revolution, humans have had a disastrous impact on the global climate, with ever increasing global temperatures and associated consequences.

Anthropogenic climate change has resulted in the mass melting of glaciers, rising sea levels, increases in extreme weather events, accelerated species extinction, changes to habitat, and much more. These all result in major changes to both the biotic and abiotic components of an ecosystem.

Destruction and Degradation of Habitat

Perhaps the greatest threat to much of the world's wildlife and natural ecosystems is the degradation and destruction of habitat, which is fueled by unsustainable human population expansions/growth and industry.

This loss of habitat results in changes to the ecosystem through the loss of animal and plant species, as well as through changes to the physical environment, such as land reclamation and the diversion or damming of rivers.

• The loss of habitat can have a significant impact on conflict between humans and large animal species, such as big cats, crocodilians, and elephants.

Poaching

The poaching of wildlife can have a major impact on certain species, particularly those that are endangered or have a limited natural distribution. While habitat destruction has become the principal threat to most species in the 21st Century, for some species (e.g., pangolins and tigers) poaching is just as much of an issue, if not more so.

Example of ecosystem disruption

The following are examples of ecosystem disruption, including climate change, habitat destruction, and poaching.

Climate change example

Anthropogenic climate change is expected to have numerous impacts on wildlife populations.

One likely impact of increasing global temperatures would be the change in the sex ratios of some reptiles, particularly crocodilians. Since egg incubation temperature determines crocodilian gender, even slight fluctuations can result in an overabundance of females and far fewer males (Fig. 1), which could result in the extirpation of some crocodilian populations.

This is of particular concern for Critically Endangered species, such as the Cuban crocodile (Crocodylus rhombifer) and Chinese alligator (Alligator sinensis), both of which have restricted distribution and could go extinct in the wild.

Habitat destruction example

As mentioned previously, habitat destruction can cause increases in human-wildlife conflict. One of the greatest threats to elephant populations in both Africa and Asia is increased conflict with humans, mostly due to the destruction and fragmentation of habitat.

This conflict involves the raiding of crops by elephants, as well as elephants attacking and killing humans, and humans killing elephants in retaliation for the loss of crops or loss of life.

Poaching example

For some species, poaching is still the major threat to continued survival. One such species is the tiger (Panthera tigris). The market for traditional folk medicine in parts of Asia has resulted in increased demand for tiger body parts and, thus, increased poaching.

In fact, within the first two decades of the 21st Century tigers have been declared extinct in Cambodia, Laos, and Vietnam, leaving Myanmar and Thailand as the only two countries in Indochina with (small) breeding tiger populations (Fig. 2).

While tiger populations have recently increased in some other areas (e.g., Nepal), it is possible that the species will disappear from Indochina entirely in the near future, mostly due to poaching to fuel this demand for folk medicine.