Native Plant Rescue Site Selection

Jay Doolittle
May 5, 2006
ES 551, Emporia State University


The Atlanta metropolitan area has been growing at a rapid pace for many years now. An inevitable consequence of this growth is that forests are being destroyed on a daily basis to make room for housing, retail, and commercial uses. Usually, the forests are clear cut without regard to the plants, animals or other resources on the property. Valuable trees may be saved for the timber but often they are just shredded on the spot and no effort is made to save any other living plants or animals that call the forest their home.

Saving all of the animals and plants from the consequences of development would be a huge undertaking and is not the subject of this project. There are organizations though that are eager to save some of the plants that grow in these forests and this project was undertaken to assist in this effort. One organization that works to save native plants from development is the Georgia Native Plant Society, GNPS. Its members seek out, and go to forests that are slated for removal so that they can rescue the valuable native plants that live there. The plants that are obtained in this way are donated to local gardens in the Atlanta area.

The GNPS currently has permission to visit and rescue plants from many properties in the area but is always looking for new sites. Usually, new sites are obtained when members drive by a plot of land that looks like it is about to be developed. Indicators may be a “For Sale” sign, survey tape, utility locate markings such as paint or flags, “Rezoning Notices,” etc. If there is a phone number posted this is recorded and then an effort is made to gain permission to establish rescue field trips to the site. These are effective means of locating and gaining access to such threatened forests but leave a lot to chance or are time consuming when one makes a special point to drive around and look for threatened forest sites. This project was undertaken to pursue another method of site selection using Geographic Information System, GIS, technologies.

GIS can integrate geographic information such as geographic coordinates of a forest likely to contain valuable native plants with other types of data such as the Parcel ID number of a tract of land for which a rezoning application or variance has been filed. Parcel ID numbers can be used to obtain property owner names and mailing addresses. GIS can provide an efficient means of identifying forests that are threatened and the necessary contact information for gaining access to the site. All that is required is a system for integrating these types of information and the raw data that will be the input.

This project makes use of several GIS systems and tools. Idrisi Kilimanjaro from Clark Labs is used to process much of the geographic and tabular data but the project also relies heavily on freely available data and processing tools via the internet. Most of the data regarding land that is threatened by development comes from various Fulton County government web sites which also provide access to ownership and contact information, aerial photos covering much of the metro Atlanta area, future land use plans and much more. The United States Geological Survey, USGS , site provides access to many different types of geographic data. A lot of this data is free though most of it comes at a cost and the user may have to wait days or weeks for their order to be processed. Free Landsat Orthorectified images were downloaded from the USGS, Earth Resources Observation and Science, EROS , site for this project. Microsoft's TerraServer web site also provides the ability to view and save orthophotos and was used extensively in the project. GPS2CAD offers a free coordinate conversion tool on their web site and this proved very helpful in converting individual State Plane coordinates used on the Fulton County GIS Interactive Map site to the UTM 16n coordinates used in the image analysis conducted with Idrisi.


The project can be divided into four parts:

    Define criteria to be used for site selection.

    Select sites.

    Acquire land owner and contact information for selected sites.

    Publish results.

Define criteria to be used for site selection.

The first step of the project was to determine the geographic boundaries for the project and the criteria to use in selecting the properties to pursue in an effort to gain the owners' permission to set up native plant rescue events.

Site selection criteria can be divided into three parts.

    Define geographic boundaries.

    Define regions that are likely to contain plants of interest.

    Define properties that are threatened by development.

Define geographic boundaries.

The geographic boundaries of the project were determined largely from need due to the high rate of development taking place in the Atlanta metro area and the availability of the data necessary for the project. There are at least 10 counties (some sources say up to 16) that make up the Atlanta metropolitan area and Fulton County is at the center of this region. Fulton County has a sophisticated GIS department, Fulton County GIS , which provides access to a lot of data and maps that are viewable and free to download via the internet. Other departments within the Fulton County government provide useful and easily accessible data as well including the Tax Assessors office and the Fulton County Department of Environment & Community Development . For this reason this project focuses on Fulton County, though future projects will seek to expand to the other metropolitan Atlanta counties. Central Fulton County contains the city of Atlanta and in northern Fulton County much of the land has already been heavily developed. There are however, thousands of acres in south Fulton that have been neglected by developers until recently. The pace of development though is now rapid in this region. From experience the author was already well acquainted with the study area and knew that the best potential for finding undeveloped forest would be in the area of Fulton County that is south of interstate I-20 and on the outside of the I-285 perimeter. This region was further restricted to the area for which fairly high resolution ortho photos were easily available and free.

Define regions that are likely to contain plants of interest.

The next step was to determine a method for choosing regions that are most likely to yield native plants of interest. Now it is true, especially in the Atlanta area, that many types of plants can be found growing everywhere in all types of different environments. However, many of these plants are not particularly desirable for ornamental gardening purposes and it is not easy to get people involved in rescuing just any plant on a strictly voluntary basis. It turns out that most of the desirable plants are usually found growing in well established older hardwood forest. What makes a plant desirable is a whole other subject but suffice it to say for purposes of this project, older hardwood forest typically will have a higher density of plants that the members of GNPS feel are worth saving. Of course there are exceptions; certain plants such as the Pink Lady Slipper, Cypripedium acuale , are most commonly found amongst pines and many interesting plants are found only in bogs or wetlands though opportunities for rescuing in wetlands are severely restricted due to environmental regulations.

Having decided to search only in hardwood forests area it is necessary to develop a method for isolating hardwood forests from other land cover types. Looking at the orthophoto images of the Atlanta area on the interactive map on the Fulton County GIS web site, it is fairly easy to distinguish hardwood forests from pine forests and other land cover types. This is especially true because of the time of the year these photos were taken, around April 6-8. At this time, most of the hardwood forests had not yet or had just begum to leaf out and are very different in appearance from any other land cover including pines. It was originally envisioned that orthophotos would be the starting point for an analysis that would isolate the hardwood forest cover type. The ideal option for acquiring this data would be to use the free digital orthophoto quadrabgle, DOQ , downloads available on the USGS Seamless Data Distribution System, SDDS , site. However the SDDS site was almost always down when it was visited it and when it was up, the author was never able to complete a successful download. Orthophoto data is also available by saving individualimages generated by using the interactive map on Fulton counties GIS web site but it would have taken many hours to resample and piece the images together all of the images needed. Another free option was investigated on the TerraServer site but still would have required too much time to piece the individual images together. It would have required a minimum of 250 separate image downloads to cover the entire study area at an acceptable resolution level. I think the use of orthophotos provides the best starting point for choosing the hardwood forest type but that will have to be done at another time.

Due to constraints of time and budget the option chosen was to use the free Landsat images that the author was able to successfully download from the USGS, EROS site. ETM+ Pan Sharpened images were downloaded and these contain satellite imagery from bands 2, 4, and 7 at a resolution of 14.25 meters. The pan sharpenned option was chosen because the image resolution is increased form 28.5 to 14.25 meters using a sharpeniong technique involving Band 8.These files were downloaded from the EROS web site and then imported into Idrisi.

ETM+ Pansharpenend Image

Signature files were generated for 5 different cover types by choosing training sites of known land cover. The land cover training sites were chosen by using the orthophoto images on the TerraServer website and making note of their locations. Using the DIGITIZE module, vector polygons were drawn on the raster Landsat images that corresponded to land covers of as high purity as possible.

This procedure was followed for each of 5 different cover types, deciduous (hardwood) forest, pine forests, pasture, water, and paved areas. MAKESIG was run using these 5 cover types as represented in each of the 3 Landsat bands. After the signature files were developed, MAXLIKE was run to classify each pixel in the image as to which signature it most closely resembled.

The resulting image had a lot of noise in the form of isolated individual pixels that didn’t belong to any of the surrounding classes. The FILTER module was run with the Mode option and a kernal size of 7 to reduce this noise by converitng the isolatted pixel values to that of the most common one in the immediate vicinity.

At this point the image consisted of 5 different classes of land cover along with some pixels, 1% of the total, that didn’t belong to any class. It should be mentioned that many variations of the above procedure as well as some completely different methods were tried before settling on the above procedure.

Land Cover Classes

Following the FILTER procedure, ASSIGN was used to convert all land cover classes except deciduous (hardwood) forest to 0 and hardwood to 1 so that a binary image was generated.

It can be clearly seen from the image generated that most of south Fulton is classified as deciduous (hardwood) forest. An effort was then made to isolate the individual forest groups and then to classify them based on size. The final product of this operation places properties in 6 different classes ranging from 0 - 10 acres in size to 1,000 - 7,000 acres. The reason for classifying forest based on size is that large forests are likely to yield many more native plants than small forest and therefore tend to have a higher pay off in terms of the amount of time spent in locating, contacting and negotiating with a property owner or developer for access to the property.

Deciduous Forests of South Fulton County

Define properties that are threatened by development.

The next phase of the project was to define properties that are likely to be developed in the near future. Several different means are available for doing this but, for this project, only one means was chosen and involves changes in zoning classification or variance that often occur prior to a property being developed. This information is easily accessible on the Fulton County web site. It may take months or even years from the time a developer begins making zoning change requests until a version of their proposal is eventually passed. The actual property development then may be delayed another few weeks, months, or years. The choice of using rezoning as a threatened property indicator then, provides a list of properties for which development is likely to occurr though it may not start for several months or more which gives GNPS rescuers time to gain access to and work with the property. GNPS prefers to work with properties that are going to be open to them for at least enough time to conduct several organized rescue events.

The Fulton County Department of Environment & Community Development site was visited where lists of poperties being considered for zoning changes were found. Zoning changes affecitng these properties were discussed and voted on at the two most recent meetings April 6, 2006 , February 2, 2006 of the Community Zoning Board in south Fulton. Of the 70 agenda items listed for these two meetings, about half of them concerned specific properties and of those,17 properties were initially identified as having the potential for rescue due to there size being not less than 10 acres.

In the rezoning notices there usually is some information that can be used to locate the property in the form of a Land Lot number or description such as “the southeast intersection of Bunter Rd and Camp Creek Pkwy". If the Land Lot number is available it is usually easy to obtain a Parcel ID number and then the State Plane Coordinates can be found by using the interactive map on the Fulton GIS website. The current Parcel ID number can also be used to obtain property records that contain the owners name and mailing address. Of the 17 properties selected from the initial rezoning list, the Parcel ID number either could not be found or there was some problem with it for 5 of the properties. For these properties, the Property Tax record file containing the owners name and mailing address could not be found. Additionally a couple of the properties were found to be in north Fulton though they were listed in the rezoning section for south Fulton. In short, 10 of the 17 properties were found to be acceptable in terms of having the necessary contact information and being within the geograhic boundaries of concern.

The property records page of each of the properties shows information about the ownership and location and it also has an aerial photo of the specific property. (Click here for an example ). This turned out to be a convenient means of satisfying the criteria of whether the property was also covered by hardwood forest. It was noticed though that there were errors in some of the property records as well as in some of the other information accessed on the Fulton county site. Some of the error associated with the property records included showing the same aerial photo of properties that were adjacent but had different Parcel ID #s and addresses. Another error was noticed in which a property’s size was listed as 0.4 acres on the Property Tax Record but the aerial photo was of a much larger tract of land. When this was checked against the size shown in the rezoning notice the area given was 22 acres.

Conclusion: Selecting Final Product

The final output of properties to pursue for permission to rescue plants is a function of the results of the identification of properties threatened by development and the land cover type identified from the Landsat images. Though it was fairly easy to visually interpret the land cover type from the aerial photo of each tract of land, this information was cross checked with forest cover output of the Landsat image, since errors were known to exist in the tax records. This table lists 10 properties that are good candidates for native plant rescues. The property owners names have been left out of this example to protect their privacy.

The final output product lists subject property locations along with their ID unique to this project. The table lists the essential information about the property including location, owner name and address, Parcel ID number and the most recent zoning case number so that its status can be followed.

Future work on this project will include expanding the list of threatened properties in Fulton County by including rezoning notices from prior years for which no development has yet taken place. Another source of information about threatened properties comes from notices of application of land disturbance permits. In this case, development is imminent so it will be necessary to have a procedure and the man power in place to quickly act before pursuing this class of threatened property.

In future work, orthophoto images will be used more extensively when they have been incorporated into a GIS software package. Orthophoto images provide much higher resolution and should therefore be able to yield much more detailed information about land cover and in particular, deciduous forest types. Additionally, south Fulton contains only a small fraction of the development taking place in the Atlanta metropolitan area and north Georgia as a whole, and it is desired that the project be expanded to these other areas as well.


Coordinate Conversion [online conversion tool]. 2006. Phoenix, AZ: GPS2CAD. Available: [April, 22-23, 2006]

Development and Public Safety Agency Inter-office Memorandum. (February 2, 2006) Atlanta, GA: Fulton County Department of Environmental and Commmunity Development. Available: [April 29, 2006]

Development and Public Safety Agency Inter-office Memorandum. (April 6, 2006) Atlanta, GA: Fulton County Department of Environmental and Commmunity Development. Available: [April 29, 2006]

Fulton County Zoning / Future Landuse Query Tool [interactive map]. 2006. Atlanta, GA: Fulton County Government. Available: [April 29, 2006]

Landsat Orthorectified ETM+ Pansharpened [computer file].(2000). Reston, VA: US Geological Survey. Available: [April 20, 2006].

Maps produced Using: Idrisi Kilimanjaro [GIS software]. Version 14.02. Worcester, MA. Clark Labs, Clark University. 1987-2004.

USGS DOQ [imagery]. (2002) TerraSeerver: Micordsoft Corporation. Available: [April 29, 2006]