Urban Design – Ecology & Systems

ENVS 6123

January 16, 2006

• Barcelona

• 8

Emerging in the literature is a dichotomy between studies that have addressed the ecology in a city16 and those that are describing the ecology of a city, researchers doing work in the urban context have posed ecology in questions. These questions ask about conditions within cities compared to those outside of the urban landscape.“Urban” vs. “natural”— These studies assumed “urban” characterized by the presence of humans and “natural” by their absence. “Urban” and “natural” environments were thus viewed by ecologists as being at opposite ends of a spectrum.Gradient analysis— Distance from the urban center often provides a useful first cut for determining whether spatial correlations exist between increasing human activity and ecological response variables.Ecological process rates—based on locating where rates of ecological processes change rapidly. For example, it is already well established that fossil fuel combustion increases nitrogen and sulfur deposition across large areas within and adjacent to industrial areas. Rapid assays of such changes could be used to delimit the urban system.Energy—the feature that distinguishes an urban ecosystem unambiguously from its surroundings is the level of energy use.

Ecology is the science that explains the relationships between living things and their environment. It also examines the relationships between and among species.

When humans are studied as well, those studies become known as human ecology. Belief systems, accumulated knowledge, technology, and the like, determine how most human needs are addressed.

Three sets of relationships must be determined: (1) the interrelationships within the natural system; (2) the interrelationships between user groups; (3) the demands made on the ecosystem by each user group.Human ecological planning uses the interior views of inhabitants and their adaptive strategies in the formulation of plans and implements these plans through the existing social organization.

Three mental models:

The city as living system. Landscapes and cities are living systems. What form would the city take if we understand it as a manifestation of natural processes? Ecosystems provide many goods and services. What would the city look like if its form were also manifestation of such life processes?

The city as experience of nature. What form would the city take if we understood nature as a vehicle for human development? The biophilia hypothesis suggests that humans tend to affiliate with other living processes for their emotional development. What would a city look like if its form were to appeal to ecological aesthetics?

The city as a particular place. The patterns and processes of ecosystems vary with location. What would a city look like if its form truly fits with the underlying landscape?

These mental models generate five patterns:

Hydrologic city. The usual underground network carries up to 90% of urban rainfall. A naturalized hydrologic system would be cheaper and more aesthetically pleasant.

Environmentally sensitive stormwater management in Prairie Crossing,

a 667-acre residential development in Grayslake, Illinois.

These measures include integrating restored landscapes into the development as a major element of the stormwater management system. The Prairie Crossing development can be expected to reduce surface runoff volumes by 65% and reduce solids, nutrients and heavy metals loads by 85% to 100%.

The Pyramid is situated in the Hollændervej/Fredensgade block in Kolding. All sewage in the block is collected, pre-treated in a small underground mechanical-biological sewage treatment plant, sterilised in an uv-ozone filter, pumped to the Pyramid, where the sewage are further cleaned by algae and plants. The total surface of the tanks is 840 m2 and the total tank volume is 460 m3. From the Pyramid, the sewage is ‘polished’ in a reed-bed and infiltrated in the ground. In principle, no wastewater leaves the block. The Pyramid was operational in 1994

Productive city. The gray city is not productive in ecological terms. In China 50% of vegetable consumed in cities are locally grown.

Productive zones in Village Homes, Davis, California

Bioclimatic city. Bioclimatic design uses the natural climatic forces to provide comfort

Transit city. Transit Oriented Development, TOD, advocates pedestrian scale development centered on bus and light rail stops. Urban TODs are located on trunk lines, neighborhood TODs are located on arterial with feeder transit lines 10 min. away

Habitat city.

To be a spatial structure of life process the city needs:preserved patches of critical areas,

preserved representative patches of all the ecosystems in the context,

a network of greenways linking all.