Conservation and Sustainable Use of the Biosphere - WBGU

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Conservation and Sustainable Use of the Biosphere - WBGU

The role of sustainable urban development in biosphere conservation E 3.8

191

Table E 3.8-1

Differences between non-urban and urban ecosystems with respect to the biosphere.

Sources: WBGU, 2000a; Trepl, 1994; Rebele, 1994

Non-urban ecosystem

Urban ecosystem

System limitation • functionally limited by the • geographically limited, eg town limit,

weakest intrasystemic

settlement boundary

relations

• but also geographically limited

(forest periphery, bank of a lake)

Biogeochemical and energy flows • energy received mainly from • import of fossil fuels, inorganic and

the sun

organic resources

• self-contained biogeochemical • high biogeochemical turnover and

cycles

generation of large quantities of wastes and

emissions

• export of wastes and emissions and

import into the environmental media

Degree of integration • causal and functional • living creatures in the area not

(System interconnection, • heavily integrated ecosystem necessarily linked by causal and

whereby each system is • corresponds to functional ecosystem functional relationships

functionally linked with the

• in an extreme case completely

sphere of influence of

disintegrated ecosystem feasible

another)

• system elements do not maintain any

‘ecological’ relationships

• corresponds to geographic ecosystem

Succession • successions of ecosystems • successions of urban biocenoses

(Sequence of various stages mainly caused internally or have a historical character and are

of development, succession of controlled subject to anthropogenic influences

plant communities in certain • succession deterministic, ie • succession not deterministic,

ecosystems over a period targeted, repeatable and not repeatable, not predictable,

of time) predictable to a certain extent most on the basis of social science

• final community often predictable studies

• final community not predictable

Invasion • generally relatively • particularly large number of alien

(Invasion of living creatures resistant to the invasion of species because of favourable distribution

into habitats that they otherwise alien species and naturalisation conditions

do not inhabit)

• number of species is generally

limited to a certain level

Stability and equilibrium • estabishment of a dynamic • states of equilibrium in urban

equilibrium under natural

biotic communities more or less ruled

conditions and over a long

out because the system will probably be

period (decades or centuries)

destroyed before the state of

equilibrium can be attained

Biodiversity • species abundance ‘normal’ • high diversity of sites, organisms

and biotic communities

can be studied in ecological terms, summarily characterized

and demarcated from non-urban ecosystems

(Table E 3.8-1). However, a clear separation cannot

be made because human settlements vary in density

and intensity of use, and there are transitional forms

and overlap areas between ecosystem types in the

peripheral areas.

E 3.8.3

Importance of a high quality biosphere for the

urban environment

The following functions of a high quality biosphere

can be cited for the urban environment:

• Urban climate function: green areas absorb excess

precipitation and contribute to cooling by means

of evaporation.With the production of oxygen, the

absorption of CO 2

and the removal of dust and

pollutants they help to improve air quality

(Häckel, 1990).

• Function of conserving urban nature: high diversity,

eg in the tree population, prevents the loss of

the populations in the case of disease. In this way,

the ecological and climatic functions of urban

nature are preserved (Reduron, 1996).

• Aesthetic and psychosocial function: urban green

areas are used for recreation and contribute to the

experience of biodiversity (Gebhard, 1993).

Because of the increasing urban population, the

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