On Landscape Ecology

What is landscape ecology and how does it fit within an urban framework?  

“Ecology”, as Richard Forman tells us, “is generally defined as the study of interactions among organisms and their environment, and a landscape is a kilometers-wide mosaic over which particular local ecosystems and land-uses recur” (Forman, 1996).  Zev Naveh in his book, Landscape Ecology, Theory and Application, refines this definition and tells us that landscape ecology is “a young branch of modern ecology that deals with the interrelationship between man and his open and built landscape”   (Naveh, 1994).   Pete August further refines this definition when he suggests that “landscape ecology is a discipline that studies how and why living organisms are distributed in the environment in the ways that they are.

Landscape ecologists are especially interested in how the components of a landscape – forests, villages, rivers – interact” (August, 2005).  Fortunately, landscape architecture has been accepted as a partner in the interdisciplinary field of landscape ecology (Ahern, 2005).  This is fortunate because much of landscape architecture theory is cradled in ecology.  The difference between ecology and landscape architecture is, as Ahern asserts, the “imperative to act” (Ahern, 2005) of landscape architecture.  While building places and altering landscapes, landscape ecology is asked to provide guidance and inform design decisions at a variety of scales (Ahern, 2005).  As landscape architecture makes it mark in the urban design realm, landscape ecology is again asked to provide a language for holistic design.

An important idea behind modern landscape ecology that begins to provide a design language is that any “living system, from the human body to the biosphere, exhibits three broad characteristics:  structure, functioning, and change.

Landscape structure is the special pattern or arrangement of landscape elements.  Functioning is the movement and flows of animals, plants, water, wind, and materials and energy through the structure.  And change is the dynamics or alteration in spatial pattern and functioning over time” (Forman, 1996).

The general principles that Forman presents are as well important to present:

Patches:  “A spatially separate instance of a given type of habitat” (Steiner, 1999).  Urbanization and natural process create patches of vegetation.  These patches may be as large as a national forest or as small as a single tree.

Edges and Boundaries:  An edge is described as the outer portion of a patch where the environment differs significantly from the interior of the patch.  Often, edge and interior elements look and feel differently.  A boundary can be either curvilinear or straight, but it influences the flow of nutrients, water, energy, or species along or across it.  Boundaries may also be artificial:  political or administrative.

          Corridors and Connectivity:  In the face of continuing habitat loss and

isolation, many landscape ecologists stress the need for providing landscape connectivity, particularly in the forms of wildlife movement corridors and stepping stones.  Corridors in the landscape may also act as barriers or filters to species movement.  Finally, stream or river systems are corridors of exceptional significance in the landscape.  Maintaining their ecological integrity in the face of intense human use is both a challenge and an opportunity to landscape designers and land-use planners.  The core of this paper, in that it deals with integrating neighborhood design with urban stream restoration, relies heavily on this principle.

Mosaics:  The overall structure and functional integrity of a landscape can be understood and evaluated in terms of both pattern and scale.  Interconnected corridors form networks.  These networks may be interrupted by fragmentation which is often associated with the loss and isolation of habitat.  The interaction, placement, and relationship between networks, edges, and patches form land mosaics.

The patch/corridor/matrix model is complementary to the adaptation of landscape ecological theory and concepts into urban planning and design (Herpsberger, 2005).   The landscape structure/functioning/change concept is an interesting way of describing an urban site with the patch/corridor/matrix model as a possible subset of that description.  An urban morphology can be determined and reinterpreted with these concept from landscape ecology as groups of buildings, open lots, streets, vegetation, movement all form a cohesive whole (Herspberger, 2005). 

A city can be described, as Forman has presented, not only as existing within a living system (as seen from a regional scale) but as itself a living system at the local scale—with all major theory and principles of landscape ecology describing that system.   Eugene Odum in his heralded book, Ecology: A Bridge Between Science and Society describes cities “as a parasite on the natural and domesticated environments, since it makes no food, cleans no air, and cleans very little water to the point where it could be reused” (Odum).  In contrast Jane Jacobs offers the idea that it is the domesticated areas that act as a drain on the city. Cities, she claims, provide the creativity and social benefits that enhance the human race and provide for our continued existence (Jacobs).  This anthropocentric view cannot be entirely ignored and in fact it is important to note that, as humans, it is virtually impossible to adopt any other view other than a human centered reality (Seed, 1999).

Although both a somewhat negative view of the contrast between the built and open environments, these notions, if viewed as opportunities, are quite congruent.  Odum’s view, likening a city to a parasite, for the most part accepts the notion that the city is a malignant living system, but a living system nonetheless.  With the creativity and knowledge base provided by the benefits of higher density living as suggested by Jacobs, there is a clear invitation for not only a move towards creating more of these high density environments, but a mandate to do so in an ecologically sensitive manner.