Ecosystems

Ecosystems: From Passive Support to Active Component

Many studies made in the fields of biology and ecology during the past few decades have progressively shown the inadequacy of a traditional representation of nature as a passive entity containing all the resources extracted by human activity and receiving all the emissions and waste produced by mankind. A description in terms of ecosystems that actively produce and allocate natural services is far more satisfactory because the role of natural systems is anything but passive. The network of ecosystems provides a great number of natural services, which are vital for the survival of the human and of the other living species. The Millennium Ecosystem Assessment (MA), following several other studies, describes the following four categories of ecosystem functions, further detailed in several ecosystem services:

• 1.
  Supporting services such as

  • the capture of solar energy and its embodiment as biomass,
  • the decomposition and recycling of organic waste,
  • the formation of soil, and
  • the fixation of nitrogen in soils
• 2.
  Provisioning services such as

  • the production of food (which makes the life of all heterotrophic organisms, including human beings, possible) and
  • the provision of biotic materials or fuel
• 3.
  Regulating services such as

  • regulation of the composition of the atmosphere,
  • climate regulation (including the redistribution of humidity),
  • regulation of the water cycle,
  • water purification,
  • pollination,
  • biological control of disease and pests, and
  • land stabilization and the control of soil erosion
• 4.
  Cultural services, including aesthetic, spiritual, educational, and recreational ones

All the services listed here contribute directly or indirectly to making our planet a suitable place to live in, for humankind and for all the other living species.

Each of these services derives from living organisms and in particular from some species that are critical in maintaining habitat stability and in supporting ecosystem services. Thus, a reduction of these species at a local level will have negative consequences on ecosystem services also at the global level.

Resilience, Resistance, Stability, and Persistence of Ecosystems

There are some properties that focus on the way that ecosystems respond to disturbance. Following C. S. Holling, we define resilience as the capacity of an ecosystem to return to the initial state after a perturbation, maintaining its essential characteristics. This emergent property of ecosystems refers to the ability of an ecosystem to cope with environmental disturbances (climate change, pollution, floods, fires, etc.), without changing its state into a qualitatively different level. For a high level of resilience, an ecosystem is characterized by a great capacity to survive shocks and, if damaged, to restore itself. This property is conferred at multiple scales by genes, species, functional groups of species, and processes interacting within the system. This process of restoration after disturbance helps ecosystem renewal and further development.

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