Parts of Any Human Ecosystem
There are four components of human ecosystems: biological,
physical, social, and built. They are
all necessary categories for human ecosystems, by definition. The one-word label for each is a convenient
shorthand that cannot instantly convey all the richness embodied in each
one.
The Parts have Parts
Take "social," for example. The comprehensive nature of the human
ecosystem framework presented by Machlis et al. (1997) gives some sense of the
variety of structures, processes, and relationships that are implied by the simple
term "social." The familiar
use of social-ecological conceptions in contemporary urban ecology have helped
biophysical scientists appreciate some of the richness that simple term stands
for. And of course those with biological
or ecological training will immediately fill in the detail implied by the terms
"biological" or "physical."
What Parts Exist in the Built Component?
Where subtlety may be missed in urban ecology is in what is
commonly labeled the built component. To
help expose some of that richness, perhaps "constructed" could be
used to refer to the "fourth component" of urban ecosystems.
Why might an alternative term be useful for the built
realm? Unfortunately "built" may
make non-specialists think of buildings or edifices. Adding the idea of infrastructure helps, of
course, since that term traditionally points to the connective tissue that
people also build. Wires, pipes, ditches,
drains, roads, streets, and rails are common features of urban infrastructure. Most of these will elicit thoughts of
engineering.
 |
| Human ecosystem model template, with linkages and specialized disciplines. Environmental components are described as either physical or constructed, to emphasize the extensive range of activities and artifacts that humans create in urban areas. |
But even extending the focus to built infrastructure may
allow people to miss important material parts of ecosystems that humans design,
shape, or unintentionally modify. The
surface of urban land may be purposefully modified for many reasons. Landforms may be shaped to alter water flow
or to improve the view. Low places are filled to provide more space for
buildings and roads, and grading is a common part of highway and railroad
construction. Cuts through hills and
mountains also are a part of the constructed environment, as are borrow
pits. The soil and subsoil excavated for
cellars, and the masses of materials removed in making the deep basements of
high rises, cisterns, tunnels, and subways are deposited elsewhere. Often the receiving sites are (former)
wetlands, or coastal margins. In some
urban situations, topsoil or turf is imported and installed over sterile or
compacted fill.
 |
| Baltimore in 1935, constructed shoreline in gray shading |
Not Missing the Construction For the Buildings.
Some of these activities and artifacts may be missed if one
uses the term built and too easily sees only edifices. Even buildings may hide infrastructure or
flows from view. For example, when one
looks at a block of handsome Baltimore rowhouses from the 19th century, the housing
residents is the obvious use. But the
rowhouses are also part of a unified system of stormwater management. The roofs slope gently to the rear of the
house, where gutters and downspouts convey the rainfall to the back yards, and
thence to the alleys behind the houses.
The alleys, with their central gutters, convey the stormwater to the
streets, and in the streets, the water was guided by the curbs into storm drains. So buildings, whose principal intention was
shelter (and social significance -- but that's another story) also participate
in a larger system of construction with the goal of water management.
While we are thinking about constructed systems for
stormwater management, it is worth pointing out that the 18th century
stormwater system involving houses was different in some ways from the 19th
century pattern noted above, and the current "on site" components of
stormwater management are different still, with their rain barrels,
disconnected downspouts, rain gardens, detention basins, and other water-sensitive
design strategies that characterize more recent developments or retrofits.
Complexity in the Built - Seeing Construction.
The upshot of all this complexity is that the term
constructed may be a more evocative term to use as the label for one of the
main components of the human ecosystem.
Each of the four components will suggest its own contributing structures
and processes, just as the human ecosystem does so well for the constituent social
systems, social-economic resources, and cultural resources. Substituting the term "constructed"
for the term "built" may on the surface seem unnecessary, but the substitute
term has value in immediately pointing to a broader array of activities and
artifacts than the making of edifices. The
alternative term helps expose equal detail in all four of the components of
urban ecosystems, not just the ones that are familiar to biologists or to
social scientists.
Background Literature:
Cadenasso, M. L., S. T. A. Pickett, and J. M. Grove. 2006. Integrative approaches to investigating human-natural systems: the Baltimore ecosystem study. Natures Sciences Societes 14:4–14.
Machlis, G. E., J. E. Force, and W. R. Burch. 1997. The human ecosystem 1. The human ecosystem as an organizing concept in ecosystem management. Society & Natural Resources 10:347–367.
