Resilience & Stability of Ecosystems (DP IB Environmental Systems & Societies (ESS))

Resilience & Stability of Ecosystems

• An ecosystem’s capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience

  • Diversity refers to the variety of species, genetic variations, habitats and ecological functions within an ecosystem

  • Resilience refers to the ability of an ecosystem to recover after a disturbance

    • High resilience = ecosystem quickly returns to its original state after disturbance

    • Low resilience = ecosystem takes a long time to recover or does not fully recover after disturbance

• Greater diversity often means greater resilience—two main reasons for this include:

  • Species redundancy:

    • Multiple species perform similar roles, so if one species is lost, others can fill its ecological role

  • Genetic variation:

    • More genetic diversity within a species can help it adapt to changing conditions

Human impacts on succession

• Human activities can divert the progression of succession to an alternative stable state by modifying the ecosystem through various activities, such as:

  • Burning

  • Agriculture

  • Grazing pressure

  • Resource use (such as deforestation)

• These activities can have both direct and indirect impacts on the ecosystem

  • They lead to changes in the biotic and abiotic components, ultimately altering the course of ecological succession within the ecosystem

    • For example, controlled fires are often used to clear land for agricultural purposes or to manage the spread of wildfires

    • However, fire can have serious negative effects on the ecosystem by killing off plants, reducing soil fertility and altering nutrient cycles

    • Similarly, agriculture and grazing can cause soil erosion, loss of vegetation cover and changes in nutrient cycling

    • This can, in turn, affect the composition of the species in the ecosystem

• These activities, which divert the progression of succession, may be temporary or permanent, depending upon the resilience of the ecosystem

  • If the human disturbance is mild and the ecosystem is highly resilient, it may be able to recover and return to its original state

  • If the disturbance is severe and the ecosystem is less resilient, the ecosystem will be permanently changed

    • This eventually leads to a new stable state with a different set of species and ecological interactions

• This is one reason why it is so important to carefully consider the environmental impacts of human activities in order to minimise their negative effects on the ecosystem

  • It is essential to protect natural ecological processes, such as succession