The Azimuth Project
Ecosystem services (Rev #1)

Ecosystem services

Idea

Many of the world’s resources, eg, clean water, in the world are not fixed pools but are constantly being replenished by the behaviour of entities in the overall ecosystem. Likewise many “processes”, eg, decomposition of wastes, are built upon ecosystem entities’ actions and behaviour. Ecosystem services is the study of how resources for human activities depend upon the general ecosystem and its constituents.

Details

The United Nations 2004 Millennium Ecosystem Assessment (MA) (see references) created a set of definitions for broad types of ecosystem services:

  1. provisioning such as the production of food and water, eg,

    • food (including seafood and game), crops, wild foods, and spices
    • water
    • pharmaceuticals, biochemicals, and industrial products
    • energy (hydropower, biomass fuels)
  2. regulating such as the control of climate and disease, eg,

    • carbon sequestration and climate regulation
    • waste decomposition and detoxification
    • purification of water and air
    • crop pollination
    • pest and disease control
  3. supporting such as nutrient cycles and crop pollination, eg,

    • nutrient dispersal and cycling
    • seed dispersal
    • primary production
  4. cultural such as spiritual and recreational benefits, eg,

    • cultural, intellectual and spiritual inspiration
    • recreational experiences (including ecotourism)
    • scientific discovery

Relationship between biodiversity and ecological services

It’s not immediately clear that large amounts of biodiversity (beyond the level of having a single species fulfilling a given ecosystem task) are necessary for the ecosystem services humanity depends on. However, it is believed that high biodiversity levels are required for a robust ecosystem which reliably provides ecosystem services. There are three major hypotheses for this:

  1. The redundancy hypothesis assumes that, whilst multiple species can play a given ecosystem role, as the number of providers of a given role decreases stress on the ecosystem increases and robustness decreases. Thus healthy natural ecosystems develop redundancy.

  2. The rivet hypothesis postulates that removing a species is analogous to removing a rivet from an aircraft wing: the first few rivets distribute their workload to other rivets with relatively little effect, but the susceptibility to further damage and overall risk increases non-linearly with the number of removed rivets.

  3. The portfolio effect postulates that, given a particular stressor or damage, different species will be affected in different ways, so that the damage to the total ecosystem is likely to be much less than if there was only one species in a given role.

In addition, there is the obvious issue that science has not identified all the subtle ecosystem services, let alone identified which species provide them. As such, maintaining the current level of biodiversity can be seen as precautionary.

References

category: [[biodiversity]]