ECOSYSTEM

Ecosystem

Option One- Field-Based Natural ecosystem

Introduction

The term ecosystem is defined by the Convention on Biological Diversity as a dynamic complex of plant, animal, and microorganism communities and their nonliving environment interacting as a functional unit. As further detailed by the convention, this definition does not specify any particular spatial unit or scale. Thus, the term ecosystem does not, necessarily, correspond to the terms biome or ecological zone but can refer to any functioning unit at any scale. The scale of analysis and action should be determined by the different functions, properties, spatial levels involved and by the issues highlighted in this entry.

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:

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

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

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.

Discussion

Water Needs of Earth's Ecosystems the primary and most critical water need is the need for sufficient water at the appropriate time and in the required amount to sustain Earth's ecosystems, of which humans are a part and on which all life depends. As water moves through the hydrologic cycle, not only is water itself transported but also energy and materials are moved through their own biogeochemical cycles, habitat is provided for aquatic organisms, and terrestrial systems are sustained. Water and freshwater ecosystems provide numerous ecosystem services to people worldwide. Ecosystem services are the wide range of benefits provided to people through the functioning of Earth's ...