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Landscaping with Native Plants
Exploring the Environmental, Social
and Economic Benefits Conference
December 6 - 7, 2004
Attachment A
Landscaping with Native Plants Research Needs
Introduction
Native landscaping is promoted as a means to
improve the quality of the air, soil and water, help to prevent
flooding, control erosion, and enhance biodiversity. Native
landscaping is also seen as a tool for sustainable urban
development, as a means for reintroducing the natural heritage of an
area, and as a vehicle for connecting urban residents to the natural
world and promoting a conservation culture.
But how well are these various attributes on
native landscaping quantified in the scientific literature? To
answer this question U.S. Environmental Protection Agency; DePaul
University’s Environmental Science Program and Institute for Nature
and Culture, and Chicago Department of Environment organized a
conference, Landscaping with Native Plants: Exploring the
Environmental, Social and Economic Benefits, in Chicago in December
2004. Researchers evaluated the scientific literature pertinent to
the Great Lakes basin to determine the current state of knowledge on
native landscaping and its environmental, social and economic
interactions. Close to 200 researchers, government officials,
development professionals, environmentalists, landscape architects,
civil engineers, natural resource managers and others reviewed the
evidence.
During the conference we found that while there
are many anecdotal stories about the benefits of native plants in
the landscape, there are very few rigorous scientific studies
quantifying the benefits. Many questions remain unanswered. Based
on a review of existing literature and on gap analysis discussions
during the conference, we developed the following native landscaping
research needs.
- How and why
does public perception of native landscaping change?
Design
- What characteristics of landscape pattern
affect public perception of native landscaping? Consider
shape, size, matrix characteristics, how it relates to the
surrounding site.
- What characteristics of composition
(design, phenology, transparency, vertical structure, color,
species mix) affect public perception of native landscaping?
Maintenance
- What maintenance or disturbance
characteristics (controlled burns, homo/heterogeneity, dormancy,
winter debris) of native landscaping affect public perception? How?
Public Knowledge
- Is there a relationship between public
knowledge of landscaping function (e.g. stormwater management,
urban habitat creation) and its acceptance?
- How does familiarity with (exposure to)
native landscaping affect preference/acceptance of native
landscaping?
- How does
childhood familiarity with native plants affect adult
preference?
- What
environmental education programs have been successful in
promoting adoption of native landscaping? How? Why?
Quantifying
- By combining existing environmental and
spatial models with econometric models (so that environmental
variables can be substituted with monetary values) can we
quantify the economic benefits of certain aspects of native
landscaping more rigorously?
- Can use values be estimated for native
landscaping? (For example, can the travel cost method be
employed to estimate the amounts people pay to visit a nicely
landscaped city park).
- How can we quantify the physical and
mental health benefits of native landscaping in economic terms?
- What are the economic benefits of native
landscaping on human behavior (e.g. labor relations, educational
and social welfare, consumption patterns)?
Costs/Benefits
- When all costs and benefits have been
aggregated, is the promotion of native landscaping economically
justified? What are the avoidance costs associated with native
landscaping? (e.g. lower air conditioning bills due to more
trees shading a house, or lower water bills due to native plants
requiring less irrigation.)
- Can avoidance costs be used as proxy
for valuation of the benefits?
- What are the evaluative tools that allow an appropriate cost/benefit
decision to be made with regard to native versus traditional
landscapes?
- Comparing air emissions during controlled burns to the
emissions associated with maintenance of traditional landscapes?
- Carbon sequestration?
- Biodiversity impacts?
- Hydrology impacts?
- Pesticide and fertilizer use?
- How many homeowners have to be persuaded
to implement native landscaping in order to realize any
significant cost savings to a municipality (like reduced
stormwater management costs.)
Hydrology – Research Questions
Water quantity and quality
- Develop quantitative data sets on
hydrologic impacts of native landscaping. Compare with amount of
water used to maintain a traditional landscape.
- Initiate studies on the water quality
improvements associated with native landscaping.
- How do the range of different native
landscaping types (for instance, rain gardens, bioswales,
prairie meadows ) compare to traditional curb, gutter and turf
landscape features in the mitigation of flooding, in impacting
stream habitat quality, pollutants, erosion in urban areas.
- When existing traditional landscapes such
as mowed turf/rip rap retention basin are retrofitted into
native plant landscaping or wetland what is the degree and speed
at which volume of water stored and water quality are modified.
- How does the use of native plants in
stormwater control features impact water quality (time of
- concentration) and quantity (runoff curves)?
Size
- All other factors being equal, what is the
relationship between the size of a landscaping project and water
quality and quantity benefits? Are several small landscaping
projects equivalent to one large one?
Plant Properties
- All other factors being equal, what is the
impact of a variety of native plants (individually and in
community mixes) on evapotranspiration (AET), canopy
interception and soil infiltration? How does this compare to
the evapotranspiration, canopy interception and infiltration of
a variety of ornamental plants and turf grass.
Maintenance
- How do a range of maintenance activities
(e.g mowing, fertilizer, pesticides, controlled burns) on
various landscape types (on a gradient from traditional to
native) impact air quality?
- What are the emissions associated with
burning of Midwestern prairies?
Modeling
- By combining existing local atmospheric
models to modify plume models, can we more accurately determine
emissions from controlled burns? Based on the above
information, what are the costs and benefits of using controlled
burns as your maintenance technique for native landscapes?)
Air Impacts
- How do native landscapes (including their constituent
plants and soil) compare to traditional landscapes in terms of air
quality impacts?
- What are the carbon sequestration rates for specific
landscape types?
- What are the emission (e.g. NOx, VOC, CH4) rates for
specific landscape types?
- What are the air particulate and contaminant removal effects
for specific landscape types?
Methodology
To carry out the
above information these are some of the Basic Information
Requirements
- Structural data from specific native
landscape types (vs. hypothetical native landscape types)
- Vegetation growth and mortality rates
- Improved leaf area estimates from various
landscape types
Species and Community Composition
- Does community structure (diversity and
relative species abundance) in a native landscaping project
impact biodiversity benefits?
Physical Form
- Do formalized
native plant gardens, designed with priority given to aesthetic
considerations, promote biodiversity? For example, do
flowerbeds of Purple Coneflowers next to Black-eyed Susans
enhance biodiversity?
Maintenance
- To what extent
do various management schemes, such as hand weeding, winter
pruning, dead-heading or other “tended garden” management
practices impact biodiversity?
Genetics
- When is it
important to use local genotypes in native plantings?
- How
important are seed genotypes in native seed selection?
- What role
do nursery cultivars play in the genetics of native
landscaping?
- What are the
genetic impacts of planted landscapes on local native gene
pools?
Ecosystem Function
- What ecosystem functions should most
concern landscaping practitioners when deciding the level of
biodiversity that they choose for projects? What is the best
way to evaluate these functions?
- When does restored biodiversity structure
contribute favorably to restored ecosystem function?
- What size is necessary for ecosystem functions to be
restored? Are exclusively native plants necessary for restored
function? Can we maximize ecosystem function with a combination of
native and non-native plants?
- How long after structural integrity is restored will
functions become viable?
Regional Biodiversity and Fragmentation
- What number of fragments and of what size
are necessary to achieve comparable biodiversity with large
tracts of land?
- Are several small landscaping projects equivalent to one
large one?
- Counter to many expectations, can fragmentation serve to
promote biodiversity by eliminating adverse affects associated with
larger tracks of land?
- Do native landscapes provide habitat for native biota, and
thereby increase the biodiversity of an area?
- Is this benefit enhanced if the landscaping is adjacent to a
natural area?
Definition and Methodology
- Are native landscaping and ecosystem
restoration appropriate comparisons – can we expect landscaping
projects to perform in a manner similar to a mature restoration?
Soil – Research Questions
Soils
- What are the necessary soil conditions for
successful native landscaping?
- Under what circumstances do soils (including urban soils)
need to be amended to facilitate native landscaping?
- What sorts of amendments are needed to overcome specific
limitations (e.g microbial inoculations, compost-teas, biosolids,
physical modifications, nutrients additions or sequestration)?
- What are the reciprocal relations between
urban soils and the communities planted by landscapers?
- Under what circumstances are native plant communities
constrained by poor soil quality?
- Under what circumstances is soil quality and structure
improved by landscaping?
Pesticides and
Fertilizers:
- Under what circumstances do native
landscapes require more or less fertilizer and pesticides than
conventional landscapes?
- Do the fates of nitrogen and phosphorous
on a native landscape differ from a conventionally landscaped
site? Are the biogeochemical mechanisms equivalent on native
landscaped and conventional sites, and how do these processes
compare?
Urban Carbon Sequestration
- What effect does higher carbon levels in
urban areas have on plant productivity in native versus
conventional landscapes?
- Do native landscapes
sequester more carbon than conventional landscapes?
- How do altered
compacted urban soils compare with other systems in regard to
sequestering atmospheric carbon.
Methodology
Experiments should account for the indirect
carbon effects of native and conventional urban landscaping, such as
the carbon produced during the manufacturing and application of
fertilizer, or benefits of reduced energy needs. (e.g. planting to
reduce the heat island effect could reduce reliance on air
conditioning and generate savings in fossil fuel emissions.)
- Are contaminants
absorbed by the plants being transferred to pollinators and
introduced into the food web?
- How effective are native plants, in
particular deep rooted ones, as indicators of contamination?
- How practical are native aquatic plants
for phytostabliziation on contaminated lakeshores compared to
traditional techniques?
- How effective are native plants for
hydrologic control?
- How much water would native species
use, given an unlimited supply?
- How effective are specific native plants in phytoremediation
compared with currently used non-native?
- What is the ability of native plants
to remediate ground water contamination?
- What is the ability of native plants
to tolerate/remediate radon, radium or other radioactive
elements?
- Are successional plantings, using a series
of communities from specialized non-natives to natives,
effective in the remediation of contaminated soils and the
rehabilitation of a native landscape?
- How do the costs of phytoremediation
compare to other methods of contaminant removal?
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