Ecosystem: Balance & Imbalance

The term ‘ecosystem’ was first used by A. G. Tansley in 1935. Tansley defined ecosystem as ‘a particular category of physical systems, consisting of organisms and inorganic components in a relatively stable equilibrium, open and of various sizes and kinds‘.

  • An ecosystem is a structural and functional unit of the nature where there is interactions between living organisms and non-living components and that determine the flow of energy and nutrients.
  • e.g. pond ecosystem, forest ecosystem, grasslands, deserts, etc.

Ecosystem stability/balance

Stability is commonly defined as a state in which change does not occur.

In ecology, ecosystem stability is defined as the ability of an ecosystem to maintain its structure (e.g. landscape, species diversity, etc.) and function (e.g. nutrient and water cycling, biomass production, etc.) over long period of time despite disturbances.

Fully developed or mature ecosystems are more stable than the immature ecosystems.

  • Mature ecosystems are considered stable because their structure and function remains more or less the same over long period of time.
  • Stable ecosystems are in a state of dynamic equilibrium in which things change but remain more or less the same.
  • Stability is the ability of a disturbed ecosystem to return to its original condition (resilience).
  • Stability is also a property of an ecosystem that causes it to resist being changed by natural events or by human interferences (resistance).

Ecosystem homeostasis/balance

  • Stability is also known as homeostasis.
  • Homeostasis is the dynamic equilibrium among the living members of an ecosystem, against environmental conditions such as wind, rainfall, nutrient availability, air quality and climate.

Immature vs Mature ecosystems

Immature Ecosystem Mature Ecosystem
Plants are small in size. Plants are large in size.
Species diversity is low. Species diversity is high.
Communities are mostly producers, few decomposers. Mixture of producers, consumers and decomposers.
Few ecological niches (generalized). Many ecological niches (specialized).
Low community organization. High community organization.
Efficiency of nutrient cycling is low. Efficiency of nutrient cycling is high.
Source Pinterest.

Factors that influence ecosystem balance/stability

Following are the factors that influence ecosystem

Factors that affect ecosystem stability.

A. Population growth and reduction factors
B. Species diversity
C. Food web complexity
D. Movement of nutrient and energy
E. Succession

A. Population growth and reduction factors

  • The factors that affect ecosystem’s stability are the factors that control the size of its populations.
  • These factors are of two types:
  • Growth factors: Factors that tend to increase population size.
  • Reduction factors: Factors that tend to decrease population size.

B. Species diversity and ecosystem stability

  • Ecosystem stability may also be affected by species diversity.
  • Species diversity is related to at least three variables: The number of different specie in an ecosystem, the number of individuals in each species, and the number of individuals of all species in a community.
  • Species diversity is high in mature or climax communities.
  • Mature ecosystem will remain at this stage until natural disaster or human intervention occurs.
  • A high level diversity is believed to confer a high degree of stability.

C. Food web complexity in ecosystem stability

  • An ecosystem with more complex food web is more stable than an ecosystem with simple food web.
  • In a complex food web, one organism has alternative source of food and energy while the number of energy source of an organism is less in a simple food web.
Source: Study.com
Source here.

D. Movement of nutrient and energy

  • Movement of nutrient and energy influences stability of an ecosystem. It occurs through food chain. Continuity of food chain maintains ecosystem balance while any disruption in the food chain interrupt ecosystem balance.

E. Succession influences ecosystem stability

  • Succession is the replacement of one community by another community in a particular area over time.
  • Succession gradually leads to a more complex community over a period of time.
  • A climax community is more diverse than a community of early stage during succession.

Imbalance in ecosystem

  • Stability is a useful concept to apply to ecosystem. It helps in understand imbalances that occur naturally or from human activities.
  • Small scale change
  • An ecosystem balance can be tilted temporarily by natural shifts in the abiotic and biotic growth and reduction factors. Small shifts in these factors in an ecosystem are fairly common. Ecosystem responds to these changes in a way that ensure the survival of the community.
  • However, drastic shifts can seriously, sometimes irreversibly causes imbalance in ecosystem.
  • Large scale change:
  • Major ecosystem perturbation may be caused by natural events (shifts in climate, floods, volcanic eruption, fires and drought, or human intervention such as mining and logging.
  • In either cases, damage to the ecosystem may be so severe that it takes years or decades for the original condition to be restored.

Human impact on ecosystems

1. Altering biotic factors

The various level of human impact brought about by disturbing abiotic and biotic factors in the environment.

a) Introducing competitors

Time to time, humans have introduced foreign species into new regions only to tackle serious problems caused by excessive growth of the introduced species.

12 pairs of European rabbits were introduced to Australia in 1839. Eat grasses for sheep. Number of rabbits in 1933 became 1 billion.

Water hyacinth was introduced in 1884 in Florida. 10 plants multiplied into 60,000 in 8 months. They clogged waterways and cost 11 million USD to clear it.

b) Eliminating or introducing predators

Humans have tendency to eliminate predators such as bear, eagles and wolves from their
habitat. Occasionally predators are introduced into the area (mosquito fish).

In 1900, wolves, coyotes, mountain lions were eliminated from Kaibab plateau, North of Grand Canyon. Number of deer increased from 4000 to 100,000. eat grasses and vegetation. Next year died.

c) Introducing disease organisms:

Humans have unknowingly introduced pathogen into new environment where there were no controls. They reproduce at a high rate and cause serious damage.

2. Altering abiotic factors

a) Creating pollution: Water pollution and air pollution caused by humans create an unfavorable environment for many organisms. Oil spillage, toxic pesticides, thermal pollution etc.

b) Depleting resources: Human pollutions may deplete or destroy resources used by other species.

Ecosystem resistance and resilience

Resistance Resilience
Property of communities to remain ‘essentially unchanged’ when subject to disturbance. Ability to return to a former successional trajectory after being degraded or deflected by outside disturbances.
Show little impact due to repeated disturbances over time. Immediately impacted by even low intensity disturbances.
Disturbance without loss. Capacity to recover from a disturbance after incurring losses.
No internal re-organization and successional change is needed. System is internally re-organizing, perhaps through a mosaic of patches that are at different stages of reassembly.
Loss of resistance can’t display early warning signal of a collapse. Loss of resilience can display early warning signal of a collapse.
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About Abulais Shomrat

Abulais Shomrat
Currently in 4th year (Hons) in the Department of Botany, University of Dhaka. Planning to have multiple careers one by one but promised to be with 'Plantlet' as long as it's primary stage remains unfinished.

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