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.

Public Perception - Research Questions

• 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?

Economics of Native Landscaping – Research Questions

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.

Air Quality – Research Questions

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

Biodiversity – Research Questions

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.)

Phytoremediation – Research Questions

• 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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