Liam Heneghan and Gerry Clabby (Fingal County Council, Dublin, Ireland)
The role of green infrastructure in facilitating energy flows
and material exchanges that sustain human habitation in urban regions is becoming
more apparent and its importance for long term urban planning is being increasingly
recognized. Open space planning (i.e., parks, wildlife corridors, urban forests)
has long been on the agenda of urban designers. In contrast, green
infrastructure serves as a way of framing discussions about the future of the
city so that green spaces in are presented alongside engineered structures (i.e.,
roads, bridges, sewers) in urban areas so both can be simultaneously regarded
as providing vital environmental services.
Green infrastructure gives metropolitan planners and
engineers a greater range of tools for mitigating urban problems. Additionally,
if more extensive green space is planned and protected in metropolitan areas then
this increases the opportunities for biodiversity conservation. Thus, green infrastructure
combines several seemingly disparate environmental strategies such as increasing
ecosystems services, enhancing biodiversity conservation, and bringing a landscape
ecological perspective to the management of urban regions where open space is
no longer considered as isolated fragments.
We provide a definition for green infrastructure as this is
a relatively new term and is used inconsistently. However, we demonstrate the
usefulness of the term “green infrastructure” as a way of integrating several aspects
of an urban ecological strategy. In particular, we argue that restoration is a critical
tactic in achieving functional green infrastructure in large metropolitan areas
where degraded ecosystems are often assailed by multiple stressors. We
illustrate progress made in the Chicago area in developing a green infrastructure
vision, and suggest a number of key knowledge gaps, attention to which may increase
our ability to translate this vision into a reality.
Green Infrastructure Defined
We define green infrastructure as the ecological features of
a human settlement that may be considered alongside traditional engineered infrastructure
to enhance ecological values and functions. Usually green infrastructure is
deployed for the benefit of the resident human populations although in the
cases of natural areas conservation the supposed benefit for people may be an
indirect one. This broad definition captures the range of uses to which the
term has been applied, from those structures and processes that augment urban
storm flow systems (Anon. 2008) to interconnected natural areas that contribute
to human welfare (Benedict and McMahon 2006). Green infrastructure builds on
previous work on ecosystems services, urban natural capital evaluation, and
open space protection by integrating these insights explicitly into landuse planning
in partnership with others involved in urban planning.
Since much open space in urban areas is currently either low
diversity turf grass or degraded semi-natural land, restoration may be a key
ingredient in increasing the ecological functioning of this land where the potential
of this land to serve as green infrastructure is recognized and thus has been incorporated
into urban planning. In order to provide a city with services required to augment,
and in some cases replace, elements of gray infrastructure, the rehabilitation
or restoration of open space will often be required. Green Infrastructure
Planning in Chicago