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Natural and Social Systems

sustainable development: a vision of development that seeks a balance among economic growth, environmental impacts and social equity.

What changes in society need to occur in order to achieve sustainable development?

How can a city achieve balance among economic growth, environmental impacts and social equity?

In order to become sustainable, cities must change their metabolism from a flow-through linear metabolism to a circular metabolism that recycles outputs to become inputs.

For example - paper -

- linear metabolism - harvests trees as the raw materials and discards it after use in a landfill.
- circular metabolism - takes used paper and uses it again as a raw material recycling outputs to become inputs.

Now let's look at some of the natural systems we interact with.

Soil: combination of sediments and decayed organic matter (humus) and empty pore space.

Erosion: incorporation and transportation of material by a mobile agent, usually water, wind, or ice.

Soils -"A critical sustaining structure for plants, animals, and human life." (Elemental Geosystems)

1. Definition

2. Soil profile - a model of soil horizons.

Soil horizons/layers - continuum from organic to mineral content the deeper you go.

3. Soil systems

Inputs to Soil Formation:
-Parent Material -
Residual Soil - type of bedrock. (granite? limestone? sandstone?)
Transported Soil - alluvial soils are sediments laid down by water - typically on the banks of rivers.
Volcanic Soils - andisols - parent material of volcanic ash lands on top of the soil.
- Plants and Animals
plants and animals are a source of organic matter (humus)
organic acids enhance chemical weathering
micro-organisms (bacteria, fungi) break down organic matter
- Formation processes of water:
water percolating down - moves and removes soluble material, leaching
evaporation makes water soak upwards causing minerals to precipitate (salinization)
- Climate - moisture and energy
weathering rates faster in warm, moist climate
more rainfall, more leaching and more vegetation
-Time - soils generally take millennia to develop, but can be eroded away in a few years
-Human component - agriculture and development

River systems - rivers are sediment transportation systems.
The more turbulent the flow of water, the more sediment the river can carry.
Damming a river interrupts the flow of sediments - causing them to be deposited in the reservoir. The fast running clear water coming out of the reservoir will scour out sediments downstream - eroding the alluvial soil deposited on the banks of the river.
Dams also interrupt the migration of fish species such as salmon, and often change the temperature and chemistry of river water so drastically as to kill of native fish species.

Endangered Fish on the Colorado Plateau

Ecosystems: A community and its environment. Includes all the interactions between living things and their physical environment. Powered by the sun, plants photosynthesize the sugars that feed all the other creatures in an ecosystem. Energy is transferred from one trophic level to another through the food chain.
----------Top carnivores----------
What are trophic levels?

The effects of pollution on the food chain:

Ecological effects of mercury


Adverse Effects of Persistent Organic Pollutants (POPs) during the Perinatal Period