ancient cities

evolved in response to urbanization and has
resulted in great diversity among the work of
landscape architects today. Landscape architects
are involved in the design and planning of large
landscapes, such as watersheds and communitywide
plans; many large urban spaces such as
parks, recreation facilities, plazas, and streets; and
many small spaces such as monuments and residential
gardens. This work in urban environments
has revealed significant ecological and social challenges
that characterize the field.
Urban Ecological Challenges
The stewardship, planning, and design of natural
environments by landscape architects requires an
understanding of landscape structure, that is, the
patterns of land form, plant, and animal species
found to be existing within a region, as well as
landscape function, the natural processes that
shape these patterns. Urban development often
dramatically alters landscape structure by displacing
native vegetation and sensitive animal species,
as well as landscape features such as wetlands,
streams, or hillsides. Although it has long been
common practice to preserve some existing landscape
structure in urbanizing areas through the
development of parks and open space reserves,
these remnants often degrade in quality over time
due to changes in the function of these landscapes.
Key natural processes, such as the migration of
plant and animal species, hydrology, carbon and
nutrient cycling, and ecological disturbances such
as flooding and fire, are typically suppressed or
radically altered in terms of frequency, extent, and
diminished beneficial impact.
The alteration of landscape structure and function
affects the ecological integrity of open spaces
as well as the quality of the overall urban environment.
Some native species may become locally
extinct due to insufficient or isolated habitat.
Others may thrive due to their adaptability
to urban conditions or the reduction of their
predators or competitors. Alterations in natural
processes, such as hydrology, may result in insufficient
quantity to meet human demand, as well
degradation of water quality due to chemicals,
fertilizers, and sediments common to urban environments.
Suppression of ecological disturbances
such as flooding and fire may result in less
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frequent, but more intense events that threaten life
and property.
Current landscape architecture practice favors
a variety of approaches designed to sustain the
urban ecosystem over an extended period of time.
A primary approach is the establishment of ecological
networks, an assemblage of connected open
space, often along streams and other hydrologic
systems, to facilitate species migration and preserve
natural hydrologic processes. Native plant
species are often advocated for designs to provide
wildlife habitat, reduce water usage, and prevent
the use of exotic species that may be invasive to
surrounding ecosystems. Efforts are made to capture
and filter storm water runoff using wetland
plants and microorganisms to enhance water quality,
and some open spaces are designed to flood as
a storm water management strategy. Efforts are
made to reduce energy consumption of projects,
both in terms of daily operations and maintenance,
to reduce greenhouse gas emissions associated
with development.
Ecological networks and sustainable processes
are most effectively achieved if these concepts are
integrated into the initial planning of urban environments,
but landscape architecture has long been
concerned with the reestablishment of ecologically
beneficial landscape structure and function in existing
cities, a sector of practice that has enjoyed
renewed interest in recent years. These approaches
often rely on the regenerative qualities of natural
processes, which if supported possess the potential
to restore landscape structure as well as address
soil, water, and air pollution. Although the restored
ecosystem is not identical to the native ecosystem
displaced by urban development, it has the potential
to be ecologically beneficial while also supportive
of the surrounding urban community.
Urban Social Challenges for
Landscape Architecture
As stewards, planners, and designers of the cultural
environment, landscape architects are concerned
with the broad range of social issues that
impact community life, with particular attention
paid to impacts from the physical environment.
Work may include the design of large spaces to
support community activities and smaller spaces
for small groups and individuals. Such work often