Natural Disruptions to Ecosystems
It seems that in this course we tend to concentrate on anthropogenic (Human) disruptions to ecosystems. Natural disruptions to ecosystems have environmental consequences that may, for a given occurrence, be as great as, or greater than, many human-made disruptions. There have even been five global mass extinctions (large numbers of species went extinct over relatively short periods of time) that were the result of changes in the environment.
Earth system processes operate on a range of scales in terms of time. Processes can be periodic, episodic, or random.
Earth's climate has changed over geologic time for many reasons.
It seems that in this course we tend to concentrate on anthropogenic (Human) disruptions to ecosystems. Natural disruptions to ecosystems have environmental consequences that may, for a given occurrence, be as great as, or greater than, many human-made disruptions. There have even been five global mass extinctions (large numbers of species went extinct over relatively short periods of time) that were the result of changes in the environment.
Earth system processes operate on a range of scales in terms of time. Processes can be periodic, episodic, or random.
- Periodic - occurring at repeated intervals (tides)
- Episodic - occurring occasionally and at irregular intervals (El Nino/La Nina every 2-7ish years)
- Random - meteorite impacts
Earth's climate has changed over geologic time for many reasons.
- Changes in ocean and atmosphere circulation patterns
- Varying concentrations of atmospheric carbon dioxide
- Volcanic eruptions
- Plate tectonics - continents "drifting" to different latitudes
Sea level has varied significantly as a result of changes in the amount of glacial ice on Earth over geological time.
Major environmental change or upheaval commonly results in large swathes of habitat changes
Wildlife engages in both short- and long-term migration for a variety of reasons, including natural disruptions.
Ecological Succession
Ecological succession is how an ecosystem responds to a change, natural or anthropogenic. It is the gradual changes in the types of species that live in an area. When we talk about succession, we usually concentrate on the gradual replacement of one plant community by another through natural processes over time.
Can a plant really grow in hardened lava?
It can if it is very hardy and tenacious. And that is how succession starts. It begins with a plant that must be able to grow on new land with minimal soil or nutrients.
Ecological succession is how an ecosystem responds to a change, natural or anthropogenic. It is the gradual changes in the types of species that live in an area. When we talk about succession, we usually concentrate on the gradual replacement of one plant community by another through natural processes over time.
Can a plant really grow in hardened lava?
It can if it is very hardy and tenacious. And that is how succession starts. It begins with a plant that must be able to grow on new land with minimal soil or nutrients.
Ecological Succession
Communities are not usually static. The numbers and types of species that live in them generally change over time. This is called ecological succession . Important cases of succession are primary and secondary succession.
Primary Succession
Primary succession occurs in an area that has never before been colonized. Generally, the area is nothing but bare rock. This type of environment may come about when
The first species to colonize a disturbed area such as this are called pioneer species (see Figure below). They change the environment and pave the way for other species to come into the area. Pioneer species are likely to include bacteria and lichens that can live on bare rock. Along with wind and water, they help weather the rock and form soil. Once soil begins to form, plants can move in. At first, the plants include grasses and other species that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area. Pioneer members of early successional species commonly move into unoccupied habitat and over time adapt to its particular conditions, which may result in the origin of new species.
Communities are not usually static. The numbers and types of species that live in them generally change over time. This is called ecological succession . Important cases of succession are primary and secondary succession.
Primary Succession
Primary succession occurs in an area that has never before been colonized. Generally, the area is nothing but bare rock. This type of environment may come about when
- lava flows from a volcano and hardens into rock.
- a glacier retreats and leaves behind bare rock.
- a landslide uncovers an area of bare rock.
The first species to colonize a disturbed area such as this are called pioneer species (see Figure below). They change the environment and pave the way for other species to come into the area. Pioneer species are likely to include bacteria and lichens that can live on bare rock. Along with wind and water, they help weather the rock and form soil. Once soil begins to form, plants can move in. At first, the plants include grasses and other species that can grow in thin, poor soil. As more plants grow and die, organic matter is added to the soil. This improves the soil and helps it hold water. The improved soil allows shrubs and trees to move into the area. Pioneer members of early successional species commonly move into unoccupied habitat and over time adapt to its particular conditions, which may result in the origin of new species.
Secondary Succession
Secondary succession occurs in a formerly inhabited area that was disturbed. The disturbance could be a fire, flood, or human action such as farming. This type of succession is faster because the soil is already in place. In this case, the pioneer species are plants such as grasses, birch trees, and fireweed. Organic matter from the pioneer species improves the soil. This lets other plants move into the area. An example of this type of succession is shown in Figure below.
Secondary succession occurs in a formerly inhabited area that was disturbed. The disturbance could be a fire, flood, or human action such as farming. This type of succession is faster because the soil is already in place. In this case, the pioneer species are plants such as grasses, birch trees, and fireweed. Organic matter from the pioneer species improves the soil. This lets other plants move into the area. An example of this type of succession is shown in Figure below.
Succession in a disturbed ecosystem will affect the total biomass, species richness, and net productivity over time.