Background

For conceptual purposes Environment Sandy Springs views the Sandy Springs Forest as being composed of four basic elements:

1) trees and their associated canopies

2) streams and creeks and their tributaries

3) sensitive areas: wetlands, critical forest habitats and ecological corridors

4) humans

Over the past year Environment Sandy Springs has worked with two nationally recognized tree and urban forestry management groups – Arborguard and the Davey Resource Group to identify the key characteristics of trees and their associated canopies that can be measured through the use of satellite imagery and GiS software. These characteristics include the ability of trees and canopies to:

1) Filter pollutants from the air which studies have linked to mitigation of chronic respiratory diseases.

2) Intercept rainfall to mitigate storm water volume and consequent issues.

3) Carbon storage which helps to mitigate the greenhouse/heat-sink effect.

4) Cooling the environment to regulate the temperature of our streams and helps to shade the environment to improve quality of life for humans.

Urban Forests such that in Sandy Springs are dependent on the regeneration and growth of the canopies in residential areas to sustain the forest as a whole. The U.S. Forest Service has estimated that 2/3 of an urban forest canopy comes from the growth of trees in residential areas – and in Sandy Springs this could be as high as 75 to 95%.

Protecting and Enhancing the Sandy Springs Canopy

The outline below was shared with the staff of the City of Sandy Springs prior to the start of the City’s land use planning effort and has been vetted for technical and cost feasibility.

Environment Sandy Springs favors the use of satellite imagery and GIS software to quantitatively analyze the impact of both the natural and built environments on the canopy of the Sandy Springs Forest. Moreover because the health of forested watershed areas and stream health are related – canopy analysis should be structured with regard to the overall watershed.

Threats to the Sandy Springs Canopy

Natural threats to the health of our Canopy: The main natural threat to the health of the Sandy Springs canopy comes from invasive species such as ivy, kudzu or privet which can impact the canopy by siphoning off crucial nutrients from the soil or eventually covering and smothering trees. The use of satellite imagery and GIS software can be used to broadly classify the health of trees and to determine their ability to perform critical eco-system functions.

Impact of residential re-development on the health of our canopy: Sandy Springs is undergoing an historic redevelopment process that is likely to last for years, if not decades. Commercial properties that were originally developed in the 1950s are being redeveloped and residential housing stock is being re-developed on almost daily basis.

A Greener Sandy Springs

The “green” nature of the Sandy Springs environment, much like the larger Atlanta Region, is what long-standing residents cite as what they like most about Sandy Springs and is what new residents cite as prominent (sometimes the singularly greatest factor) in the decision making process to relocate here versus more suburban settings where subdivisions are relatively devoid of mature vegetation.

Understandably re-development is necessary for the long term viability of the Sandy Springs community but policies need to be enacted that will also protect the environmental integrity of the forest in which we all live. Environment Sandy Springs believes that past efforts to balance re-development and environmental interest have failed because there was no understanding of how residential re-development impacts the health of the canopy. The’s effort to redefine its Land Use Plan offers an excellent opportunity to reboot our community’s effort to balance the requirements of commerce and the environment.

The Nature of Re-development

Residential re-development involves three types of projects:

1) The most common is the one-for-one replacement project which as the name suggests is simply a teardown of an existing structure and construction of a new structure.

2) Subdivision of existing large properties so that two or more structures at a higher density can be built.

3) Assemblages, as the name suggests, involves the purchase and re-development of multiple properties, typically at a much higher density.

Under the City’s somewhat complex re-development regulations, which contain incentives, prohibitions and exceptions, the long-term target canopy target is 35%, but the City has no data to indicate the actual level of canopy preservation nor do they have any data regarding the cycle time for the canopy to return to its original state. The City has no database mechanism to determine when and if a residential redevelopment project is so intense that the result is a permanent loss of canopy.

The commercial re-development prior to City’s incorporation resulted in a significant loss of canopy, which as mentioned in other sections – is linked to specific respiratory health problems. Thus, better planned commercial re-development could actually enhance the canopy as well as improve watersheds and water quality.

Generating Data that can be used in the land use decision-making process: The City’s current emphasis on form-based zoning, which is nothing more than models or templates that a developer must use, creates in an outstanding opportunity to develop development models that are environmentally sensitive.

Why such optimism?

1) We believe that land acquisition costs, construction costs and market price points result in re-development projects that have similar footprints.

2) Quantitative analysis using satellite imagery and GIS software can be used to define an environmental footprint based on a property’s ability too return to its pre-construction level of canopy coverage in the shortest possible cycle time.

3) By quantitatively defining both the environmental and re-development footprints and then reconciling the two, the City could create development models that are environmentally sensitive.

How can the City create environmentally sensitive development models?

It is technically feasible to utilize 2007-2015 satellite imagery data to define the typical re-development footprint for one-for-one replacement projects, assemblages, and sub- divided projects as well as the cycle time for the canopy of those redeveloped properties to return to its original state.

It is also technically feasible to calculate the environmental footprint necessary for the canopy to return to its original state in the shortest and feasible cycle time. The difference between the two footprints is currently the subject of negotiations.

(Because 80% of the problems are caused by 20% of the data points (Pareto’s Principle), agreeing to a model could be easier than one might anticipate.)