Urban Ecosystem Analysis Miami-Dade County UDB and the City of Miami, Florida

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1 May 2008 Urban Ecosystem Analysis Miami-Dade County UDB and the, Florida Calculating the Value of Nature Report Contents 2 Project Overview 2 Background 4 Major Landcover Change Findings Landcover Analysis Landcover Change Analysis 15 Recommendations 16 About the Urban Ecosystem Analysis

2 Regional Ecosystem Analysis: Miami Dade County and the, Florida Project Overview The local agencies were concerned that recent losses in tree canopy cover due to hurricanes, citrus canker eradication, and urban development had a negative impact on air and water quality and stormwater runoff mitigation. The and Miami-Dade County engaged American Forests to conduct an Urban Ecosystem Analysis to quantify changes in landcover and the resulting impacts on ecosystem services green infrastructure provides. With additional funding provided by the State of Florida Division of Forestry, American Forests conducted an Urban Ecosystem Analysis of 447 square miles within the Miami-Dade County Urban Development Boundary (UDB) line. The (48 sq. miles) was included within this larger study area. The findings show that the loss of vegetative landcover over the last decade decreased the air and water benefits the landcover provided. The loss of tree cover between 2004 and 2006, during a very active hurricane period exacerbated the trend of canopy loss. This study quantified the landcover changes due to urban development and hurricanes and their ecological impacts. The evidence presented along with the data and tools included in this project will provide the City and County s leaders with the rationale and the capacity to better integrate natural systems into future policy decisions. By investing in Miami-Dade County s urban tree cover this natural capital also saves money managing air and water, helps meet environmental regulations and fulfills the environmental protection stipulated in the Miami-Dade County Comprehensive Development Master Plan (CDMP) and in the City of Miami Tree Master Plan. The Urban Ecosystem Analysis in this study analyzed the ecology of landcover at two scales and spanned two time periods. The assessment used high resolution (1 meter pixel resolution), digital data to measure changes in landcover when Hurricanes Katrina and Wilma battered the County. The data resolution was sufficient to visually distinguish between tree canopy loss due to hurricane damage and development. The second assessment measured landcover changes using moderate resolution (30 meter pixel resolution) from Landsat satellite imagery taken in 1996 and This analysis provided a ten year trend of tree loss and urban gain, most likely due to development. While the resolution of Landsat data is too coarse for analyzing district or neighborhood scale areas, this temporal analysis can also be a good predictor of future development trends if current development policies continue. Data from this project fits seamlessly into the County s Geographic Information System (GIS) and gives Miami-Dade County and the staff the ability to conduct their own assessments for on-going planning decisions. From a broader perspective, the urban ecosystem analysis offers county leaders a way to strengthen the connections between urban and natural systems. Background Miami-Dade County is part of the Everglades ecosystem which stretches from the Kissimmee River south to Florida Bay. This unique US Ecoregion is characterized by its flooded grasslands and rich wildlife that resides within this natural ecosystem. The county is home to the Everglades and Biscayne National Parks as well as providing thriving agricultural and tourism industries. The natural areas within the County are critical for recharging the Biscayne aquifer, south Florida s sole source of drinking water. The County is also subject to annual tropical storms and hurricanes, destroying property and the very green infrastructure that protects its shorelines. Humans have further changed the land with drainage projects, waterway channels, and agriculture practices. Since the County is located in a unique geographical area, surrounded by major water bodies and a water table that sits just a few feet below ground, land is particularly susceptible to flooding from major rain events and storm surge. Urban development has exacerbated flooding in some cases to the detriment of people and property. Efforts by Miami-Dade County to address the highly impacted flooded communities within its jurisdiction have been ongoing since 1991 with the creation of its Stormwater Utility to fund Capital Improvement Projects designed to reduce stormwater runoff impacts. A third major impact on the County s urban forest has been the trees removed as part of the eradication program for citrus canker, a highly contagious bacterial disease that causes premature leaf and fruit drop. The state instituted an eradication program in 1995 to remove infected trees, as well as healthy citrus within the susceptible range. An estimated 466,000 trees have been removed within Miami-Dade County (Florida Dept. of Agriculture). Hurricane Wilma may have spread the disease to an estimated 168, ,000 acres of commercial citrus statewide and additional mortality of citrus trees in urban areas may occur in the near future. The USDA deemed eradication was no longer possible and the removal program was stopped Footnote: American Forests conducted an initial Urban Ecosystem Analysis (UEA) of unincorporated Dade County (townships that are at least 50% unincorporated) in The methodology used aerial imagery and site sampling to extrapolate landcover composition and ecological benefits for the entire study area. This methodology has been updated using much more sophisticated multi-spectral satellite imagery and updated GIS technology. Because of the differences in study area and methodology the original study does not compare to this current one. 2

3 American Forests Report in 2006 (FL Dept of Agriculture and Conservation Services press release 1/11/06) (see maps on pages 7 and 13). Urban forests provide enormous environmental benefits among them improving air and water quality and slowing stormwater runoff. Miami-Dade County is indicative of tree canopy decline trends seen in many U.S. metropolitan areas over the last few decades. American Forests has analyzed the tree cover in more than a dozen metropolitan areas and documented changes. Over the last 15 years, naturally forested areas of the country located east of the Mississippi River and in the Pacific Northwest, have lost about 25% canopy cover while urban surfaces increased about 20%. American Forests recommended that all metropolitan areas analyzed increase tree cover. Communities can offset the ecological impact of land development by planting trees and utilize their natural capacity to clean air and water and slow stormwater runoff. American Forests developed the Urban Ecosystem Analysis so that communities could: Measure tree canopy and quantify changes over time Quantify their ecological benefits and calculate their dollar value Communicate the positive impacts urban ecosystems have on reducing built infrastructure costs, while increasing environmental quality Use the GIS-based tools and data provided with this project to incorporate trees and other vegetative landcover into conservation and land use planning Adopt policies that maximize the use of natural systems into urban development, thereby building resiliency into development and natural disasters. Trees: The Green Infrastructure The physical framework of a community is called its infrastructure. Green infrastructure includes vegetation and their complex interactions with soil, air and water systems. As defined in this project, green infrastructure categories are tree canopy, open space/grass, bare soil, and water. Green infrastructure is porous, allowing water to soak into soil which naturally filters pollutants before entering the watertable. Green infrastructure is a natural system that provides many environmental benefits to a community including slowing stormwater runoff, improving water quality, protecting soil from erosion, improving air quality, and storing atmospheric carbon. Gray infrastructure is impervious, forcing water to runoff which must be managed and cleaned before entering rivers. Examples of gray infrastructure typically found in urban areas include buildings, roads, utilities, and parking lots. While both gray and green infrastructure are important in a city, communities that foster green infrastructure and integrate natural systems wherever possible are not only more attractive, they produce fewer pollutants and are more cost effective to operate (Building Greener Neighborhoods: Trees as Part of the Plan, HomeBuilder Press; 1995). Green infrastructure is important in an urban environment because it offsets the negative effects of carbon in the atmosphere. Excess carbon is released when fossil fuels like coal and gasoline are burned to release energy and that carbon, in the form of carbon dioxide-co2-a greenhouse gas, blankets the earth and causes temperatures to rise. By reducing fossil fuel consumption and the activities that release greenhouse gases; tree planting becomes one way to help slow global warming. Using Satellite Imagery and GIS to Measure Green and Gray Infrastructure While local governments commonly use geographic information systems (GIS) to map and analyze their gray infrastructure, they typically have not integrated trees and other elements of the green infrastructure. Reasons for this include 1) the lack of means to calculate the ecological and economic value of trees and other environmental features, and 2) the lack of a data set to readily use this information in existing GIS. This project addresses both of these impediments. Calculating the ecosystem services provided by tree canopy cover is available from data provided by researchers with the U.S. Forest Service, the Natural Resources Conservation Service, the Environmental Protection Agency and Purdue University. Different scales of satellite imagery are useful for determining urban landcover and ecosystem benefits. The hurricane analysis used 1 meter high-resolution satellite imagery taken in two years. The 2004 image, a mosaic of several images collected from November 2004-February 2005,was provided by South Florida Water Management District; the March 2006 CIR imagery was provided by Miami-Dade County and was resampled to 1 meter resolution to match the 2004 data. The imagery at this resolution is used to create a digital representation of a County s green infrastructure. This green data layer integrates well with other County GIS data layers and the 2006 data can be used for daily land use planning and management. The Landsat satellite provided a ten year historic temporal change trend. The imagery collected in 1996 and 2006 was classified into digital data sets with five landcovers for comparison: tree canopy, open space/grass, urban, bare soil, and water. The data, software tools, and training provided with this project allow the County and City staff to conduct their own analyses and connect landcover with the environmental benefits they provide. 3

4 Regional Ecosystem Analysis: Miami Dade County and the, Florida Major Landcover Change Findings Tree canopy declined between 2004 and 2006 in the County s Urban Development Boundary. The loss was due primarily to development and exacerbated by hurricane-related damage. The analysis compared landcover changes from 2004 and 2006, during an active hurricane period and found a 1,900 acre (3%) loss in tree canopy, and a 780 acre (1%) loss in open space. In 2006 the UDB had 18% tree canopy cover, 25% open space and 41% impervious surface. The greatest percentage of tree canopy loss was in the northern part of the county due to Hurricanes Katrina and Wilma. County Districts 1 and 4 lost the greatest percentage of tree canopy measuring 171 acres (6%) and 320 acres (8%) respectively. The data also analyzed what type of landcover the tree loss converted to. A visual inspection of the data observed whether the tree canopy change was due to hurricane damage or development. For example, tree canopy that changed to bare soil indicated land clearing for development, and bare soil that converted to impervious indicated new development. Tree canopy also converted to impervious land cover. Overall 2,639 acres that converted to one of these categories indicated development. In contrast, less than half the area (1,230 acres of tree canopy) converted to open space, which indicated loss was due to hurricane damage. Examples of these landcover changes are on page 8. Loss of tree canopy and open space between 2004 and 2006 has ecological consequences, because this loss of green infrastructure means the County s natural environment is less able to provide ecosystem services for air, water, and carbon. Trees improve air quality by removing nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3) and particulate matter 10 microns or less (PM10) in size. The Miami-Dade County area inside the Urban Development Boundary s (UDB) vegetative landcover lost its ability to remove approximately 218,000 pounds of air pollutants annually, valued at $550,000 per year. Trees have a direct impact on the carbon footprint. Trees help clean the air by storing and sequestering carbon in their wood. Total storage and the rate at which carbon is stored (known as sequestration) can be measured. The loss of tree canopy inside the UDB equated to a loss in 83,000 tons of carbon stored in trees wood and a loss of 643 pounds of carbon sequestered annually. Note: The two data sets are at different scales and time periods so that the numbers will be different. The data is more detailed and thus better reflects land cover figures provided. Trees slow stormwater runoff, reducing peak flows and decreasing the amount of stormwater storage needed. There was a loss in stormwater retention capacity due to the loss in tree canopy. Miami-Dade County uses Best Management Practices (BMPs) to control stormwater runoff and maintain water quality. The value of BMPs is determined on a site by site basis and costs vary by land use and technique used. In residential areas of the UDB, 13.7 million cubic feet of stormwater has been controlled using BMPs at a value of $96 million. In commercial and industrial areas, 4.8 million cubic feet of stormwater was controlled at a value of $52 million Between 2004 and 2006 the lost 127 acres (3%) of tree canopy and 36 acres (1%) of open space during this time period. Impervious surface increased by 163 acres (1%). The greatest percentage of loss occurred in District 5 (3.6%) followed by Districts 1 and 2 each with 3% loss. As a result, Miami s tree canopy lost its ability to remove 14,500 pounds of air pollutants annually, valued at $36,500. The loss also reduced the ability of trees to store 5,500 tons of carbon and sequester 43 pounds of carbon annually. Loss of tree canopy decreased the s natural capacity for water retention. Applying the same BMP values for the, in residential areas, 931,000 cubic feet of stormwater was controlled at a value of $6.5 million. In commercial and industrial areas, 182,000 cubic feet was controlled, at a value of $2 million Between 1996 and 2006 Miami lost 15 acres of tree canopy (4%) and 13 acres of open space (2%) and gained 10 acres of urban land (6%) and 11 acres of bare soil (7%). Miami s tree cover lost its ability to remove 1,600 lbs of air pollutants annually at a value of $4,000 and there was a loss of 620 tons of carbon storage and 5 lbs of carbon sequestered annually. The city had a 247,000 cubic foot loss in stormwater storage capacity. Of eight quantified water pollutants, the pollutant loading of each worsened by.1% to.3%. 4

5 American Forests Report Temporal landcover changes between 1996 and 2006 indicate significant tree canopy loss due to development The analysis using Landsat satellite data revealed that within the UDB there was a 17% and a 9% decline in tree canopy and open space respectively, while there was a 6% and 7% increase in urban areas and bare soil respectively. During this time, the County lost 6,800 acres of tree canopy and 5,700 acres of open space. There was a concurrent gain of 10,000 acres of urban land. Since the most dramatic pattern of change occurred along the western perimeter of the UDB (see page 10), these changes were most likely due to development. The decline trend of Miami-Dade County vegetative cover and increase in urban areas within the UDB has ecological consequences for today but also ecological opportunities for the future Within the County s UDB there was a loss of 131 million cubic feet of stormwater retention capacity during this time period due to tree canopy decline. During the ten year time frame of this study, Miami-Dade County tree cover within the UDB lost its ability to remove approximately 767,000 pounds of air pollutants annually, valued at $1.9 million per year. The loss in tree canopy inside the UDB since 1996, equates to a loss in 291,000 tons of carbon stored in trees wood and a loss of 2,300 pounds of carbon sequestered annually. Tree roots absorb water pollutants; eight of which can be measured: Biological Oxygen Demand, Cadmium, Copper, Lead, Nitrogen, Phosphorus, Suspended Solids, and Zinc. This study calculated that each worsened by between 1% and 5% because trees were removed from the land. These percentages are calculated from the stormwater runoff changes (see page 13). Hurricane Katrina hit Miami-Dade County on August 25th, Hurricane Wilma passed through Palm Beach County on October 25th, 2005; it s damage extended into Miami- Dade County Landcover Analysis A few hours before landfall in south Florida on August 25th, 2005 Hurricane Katrina strengthened to become a category 1 hurricane. Landfall occurred between Hallandale Beach and North Miami Beach, Florida, with wind speeds of approximately 80 mph. An analysis by NOAA s Climate Prediction Center reported that parts of the region received more than 15 inches of rainfall which caused localized flooding and damage to property and tree canopy. Just two months later, Hurricane Wilma slammed into Palm Beach County on October 25, 2005; its damage extended into Miami Dade County. Miami-Dade County and the wanted to determine the extent of tree canopy loss attributable to recent hurricane damage within the Urban Development Boundary and quantify the environmental impacts the loss has had on air and water. An analysis was conducted using satellite imagery taken prior to and after Hurricane Katrina. The South Florida Water Management District provided the 2004 color 1 meter infrared imagery that was taken between November 2004 and February 2005 with an ADS 40 digital camera. The 2006 imagery was provided by Miami-Dade County with a CIR imagery collect in March. The imagery was resampled to 1 meter to match the earlier imagery resolution. Both sets of imagery were then classified into five landcovers: tree canopy, impervious, open space, bare soil, and water. Table 1 details the change in these five landcovers of the County within the UDB over the two year period. There was a 3% decline in tree canopy representing a loss of 1900 acres inside the UDB. The County also lost 780 acres of open space and 436 acres of bare soil. The County increased its impervious land by 2,900 acres. Table 2 details landcover changes within the. Loss of Air Quality Ecosystem Services The loss of pervious landcover (trees, open space, and bare soil) and increase in impervious surface (buildings, roads, etc.) means that the natural landscape provided less ecosystem services to the community. Table 3 details the loss in air and carbon ecosystem services in both the County within the UDB and in Miami. The data is further sub-divided into 13 county districts and 5 city districts. For the County, the loss means that 218,000 pounds of air pollutants valued at $550,000 annually were not removed. The dollar value is calculated based on externality costs these are costs borne to society as a negative impact of the additional air pollution. Externality values are established by State s Public Service Commissions and costs associated with respiratory illness and hospital stays are factored into the cost calculation. Also, there was a loss in carbon storage of 83,000 tons and 643 fewer pounds of carbon are sequestered annually offsetting atmospheric increase in carbon dioxide, a contributor to global warming. 5

6 Regional Ecosystem Analysis: Miami Dade County and the, Florida Table 1: Miami Dade County UDB Landcover Changes 2006 Percent Acres of Total Percent Landcover Acres Acres Change Landcover Change Trees 56,681 54,780-1,901 18% -3% Open space/grass 79,056 78, % -1% Bare Soil 6,304 5, % -7% Impervious 122, ,300 2,894 41% 2% Water 44,879 45, % <1% Total Acres 309, % Table 2: Landcover Changes 2006 Percent Acres of Total Percent Landcover Acres Acres Change Landcover Change Trees 5,047 4, % -3% Open space/grass 3,824 3, % -1% Bare Soil <1% <1% Impervious 14,097 14, % 1% Water % 2% Total Acres 23,372 23,371 Note: The city totals are calculated from adding the UEA results of each District Table 3. UDB Loss of Air and Carbon Ecosystem Services Loss of Air Tree % tree Loss of Air Pollution Loss of Loss of 2004 Tree 2006 Tree canopy canopy Pollution Removal Carbon Carbon Area Canopy Canopy change change Removal Value Stored Sequestered Miami Dade UDB acres acres acres acres lbs. annually dollar value tons lbs. annually District 1 20,773 2,652 2, % -19,409 -$49,010-7, District 2 16,114 2,475 2, % -13,217 -$33,375-5, District 3 16,354 2,166 2, % -9,042 -$22,832-3, District 4 16,000 4,017 3, % -36,181 -$91,362-13, District 5 8,210 1,345 1, % -5,069 -$12,800-1, District 6 16,114 2,475 2, % -13,217 -$33,375-5, District 7 26,757 11,088 10, % -17,970 -$45,375-6, District 8 40,001 9,814 9, % -30,129 -$76,079-11, District 9 33,368 4,960 4, % -15,980 -$40,351-6, District 10 15,736 2,992 2, % -13,161 -$33,233-5, District 11 20,602 3,499 3, % -15,241 -$38,484-5, District 12 34,935 5,664 5, % -25,110 -$63,404-9, District 13 15,411 2,093 2, % -3,958 -$9,995-1, TOTAL 280,375 55,240 53,345-1, ,684 -$549,675-82, Note: Areas of each District that contain Biscayne Bay or the Atlantic Ocean were excluded from this analysis District 1 4, % -2,131 -$5, District 2 7,290 2,271 2, % -8,056 -$20,342-3, District 3 2, % $1, District 4 4, % $1, District 5 4, % -2,908-7,343-1,105-9 TOTAL 23,375 5,008 4, ,460 -$36,513-5, Note: Areas of each District that contain Biscayne Bay or the Atlantic Ocean were excluded from this analysis Between 2004 and 2006 the lost 3% of its tree canopy representing 127 acres (Table 2). The City also lost 36 acres of open space and gained 163 acres of impervious surface. The loss means that 14,000 pounds of air pollutants valued at $36,500 were not removed. There was a loss of 5,500 tons of carbon storage and 43 fewer pounds of carbon are sequestered annually. 6

7 American Forests Report County and City Tree Loss by District Tree canopy loss within the Urban Development Boundary was subdivided by County and City Districts (see page 8). Note that County Districts that extend beyond the UDB are not included in this study. The district colors in the graphic represent the percent loss of tree canopy between 2004 and County Districts 1 and 4 had the highest percentage of loss, with 6% and 8% respectively. A visual inspection of the data suggests that hurricane damage was greatest in these districts which were in the path of Hurricane Katrina and closest to the coast, where windspeed was likely the strongest. Hurricanes typically lose windspeed as they move in-land and tree loss due to hurricane damage appears consistent with the graphic depicting tree loss. The portion of Districts 4, 8 and 12 within the UDB lost the greatest acreage of tree canopy. Of particular interest is to observe what the tree canopy converted to. The pie charts within each district represent what the tree canopy loss was replaced with. While the analysis of data can t directly distinguish the cause of tree loss a visual inspection of the change in land cover offers some indicators. A visual comparison (see page 8) indicated that tree canopy replaced by bare soil was typically land clearing as part of pre-development. Likewise, water area increased indicating development in process. Tree canopy replaced by impervious was typically development. In contrast, a visual inspection of the data showed that tree canopy replaced by open space was due to hurricane damage. Thus, by quantifying what tree canopy was replaced with provided a good indicator of its cause of loss. During the two year time period more than twice the acreage of tree canopy was replaced by either bare soil or urban (2,639 acres) compared to trees replaced by open space (1,230 acres). While Hurricane Katrina exacerbated tree loss inside the UDB, development was the primary cause of tree canopy loss Citrus Tree loss due to Citrus Canker This map represents data provided by the Florida Department of Agriculture. It represents the incidence of citrus tree removal during the state eradication program. Tree loss due to citrus canker was included high resolution data analysis. Since the city had been mostly developed prior to this time frame, overall tree loss was less than in the UDB. A visual inspection of the imagery shows that tree canopy was primarily lost to urban development. The proportion of change to urban, open space, bare soil, and water are noted in each District s pie chart. 7

8 Regional Ecosystem Analysis: Miami Dade County and the, Florida Tree Canopy Loss by Districts Tree canopy loss within the Urban Development Boundary was subdivided by County and City Commission Districts. The pie charts within each district represent what the tree canopy loss was replaced with. A visual inspection of the change in land cover offers some indicators: tree canopy replaced by bare soil was typically land clearing as part of pre-development; water area increased formed during development; tree canopy replaced by impervious was typically development; and tree canopy replaced by open space was mostly likely due to hurricane damage. While Hurricane Katrina exacerbated tree loss inside the UDB, development was the primary cause of tree canopy loss. 8

9 American Forests Report 2006 Landcover This map represents Miami-Dade County landcover data taken from high resolution satellite imagery and then classified into five different landcover classes. These data are used with CITYgreen software to calculate the ecological and economic benefits that tree canopy provides in slowing stormwater runoff, improving air and water quality and storing and sequestering atmospheric carbon. 9

10 Regional Ecosystem Analysis: Miami Dade County and the, Florida Landcover Changes A visual inspection of the high resolution imagery for changes in land cover can reveal the cause of tree canopy loss from either hurricane or development. The pie charts inset in each image indicate the relative changes in landcover within this view. In the 2004 image (left) an existing golf course in County District 1 displays tree canopy. In the 2006 image (right) only the tree canopy is affected, indicating hurricane damage. In the 2004 image (left) a fruit grove in County District 8 dominates landcover with some bare soil indicating pre-development of a road. In the 2006 image (right), much of the tree canopy is replaced with homes and roads. 10

11 American Forests Report In the 2004 image (left) an existing residential neighborhood in County District 4 shows trees, which in the 2006 image (right) is greatly affected by tree loss indicating hurricane damage. Table 4. UDB Loss of Commerical and Industrial Stormwater Ecosystem Services Commercial and Commercial and Industrial Stormwater Commerical and 2004 Tree Canopy 2006 Tree Canopy Tree canopy change Industrial Stormwater BMP Value Industrial Land in landuse category in landuse category in landuse category BMP $11 per cu. ft Miami Dade UDB acres acres acres acres cu. ft. dollar value District 1 2, ,940 $6,236,340 District 2 2, ,113 $1,904,244 District 3 1, ,025 $1,188,276 District 4 1, ,737 $3,231,105 District 5 1, ,417 $455,587 District 6 1, ,308 $1,279,384 District 7 1, ,184 $904,027 District 8 1, ,425 $3,524,673 District 9 2, ,381 $7,451,189 District ,491 $1,611,400 District ,602 $6,221,621 District 12 8, ,512,059 $16,632,648 District 13 1, ,936 $1,649,291 TOTAL 26,910 1,911 1, ,753,618 $52,289,785 District ,277 $212,045 District ,588 $1,007,466 District ,841 $64,256 District ,420 $147,619 District ,109 $573,197 TOTAL 2, ,235 $2,004,583 11

12 Regional Ecosystem Analysis: Miami Dade County and the, Florida Stormwater Ecosystem Services Trees slow stormwater runoff by intercepting water on leaves, branches, and absorbing it through root systems. The loss of tree canopy increases the amount of stormwater that must be managed. Florida is unique in that it has a very shallow water table and is surrounded by water the Atlantic Ocean and the Everglades, thus all the water drains into waterbodies or through percolation into the watertable. There is also mounting concern for rising sea levels due to global warming, which would further strain stormwater management efforts and cost. The Miami-Dade County Comprehensive Development Master Plan s Conservation Element provides for the conservation, environmentally sound use, and protection of all aquatic and upland ecosystems and natural resources, and protects the functions of the aquifer recharge areas and natural drainage features in Miami-Dade County. In urban areas, stormwater engineers have employed water quality best management practices (BMPs) into the design of drainage and water pollution prevention facilities. Design techniques to manage storm water runoff include French drains, wet detention, dry detention, swales, drainage wells, and pollution control structures. Systems are designed to infiltrate either first-in stormwater runoff, a 5-year/24 hour storm, or a 10-year/24 hour storm. In this study a 5-year/24 hour storm rainfall figures were used along with County-provided BMP dollar values for residential ($7 per cubic ft. average) and commercial/industrial areas ($11 per cubic ft. average). Tables 4 and 5 detail the BMP values for handling stormwater runoff inside the UDB and in Miami. Equating tree canopy loss to stormwater management, the County manages 4.7 million cubic feet of stormwater in commercial, and industrial areas, valued at $52 million and 13.7 million cubic feet of stormwater valued at $96 million in residential areas. These values are further sub-divided by county and city districts. Protecting and enhancing forest canopy along with employing BMP techniques offer a two-pronged approach to stormwater management. The city manages 182,000 cubic feet of stormwater in commercial, and industrial areas valued at $2 million and 931,000 cubic feet of stormwater valued at $6.5 million in residential areas. Table 5. UDB Loss of Residential Stormwater Ecosystem Services Residential Stormwater 2004 Tree Canopy 2006 Tree Canopy Tree canopy change Residential Stormwater BMP Value Miami Dade UDB Residential Land in landuse category in landuse category in landuse category BMP $7 per cu. ft Residential Land acres acres acres acres cu. ft dollar value District 1 7,574 1,298 1, ,988 $3,604,917 District 2 68,890 1,607 1, ,020 $4,277,141 District 3 5,335 1,317 1, ,976 $4,836,829 District 4 6,119 1,603 1, ,274,002 $8,918,015 District 5 3, ,165 $1,660,158 District 6 6,431 1,965 1, ,127 $2,338,887 District 7 12,889 5,991 5, ,067 $6,804,468 District 8 17,087 4,404 4, ,707,496 $18,952,474 District 9 9,588 1,122 1, ,029,856 $28,208,992 District 10 7,667 1,841 1, ,471 $5,407,296 District 11 7,534 1,463 1, ,092 $4,032,647 District 12 5, ,513 $4,700,589 District 13 6,315 1,120 1, ,666 $2,132,659 TOTAL 164,043 25,302 24, ,696,439 $95,875,072 District 1 1, ,674 $746,719 District 2 2,570 1,072 1, ,148 $3,704,039 District 3 1, ,549 $409,842 District 4 2, ,916 $475,413 District 5 1, ,490 $1,179,430 TOTAL 9,867 2,805 2, ,777 $6,515,443 12

13 American Forests Report Landcover Change Analysis using Landsat Data American Forests classified Landsat TM 30 meter pixel satellite images from 1996 and 2006 to show the change in landcover inside the Urban Development Boundary line over a 10 year period (see page 14). There was a 17% loss in tree canopy and a 9% loss in open space. At the same time there was a 6% increase in urban areas and 7% in bare areas. Tree loss occurred primarily in the western perimeter of the County within the UDB, in Districts 9, 11, and 12 as indicated in red in the graphic. The pattern of tree loss is most likely the result of development and the citrus canker eradication program. Due to the landcover changes, the County lost $1.9 million in annual air pollution removal value, and 291,000 tons of carbon storage and 2,300 lbs of sequestration annually. The temporal analysis provides valuable public policy information showing general trends in landcover changes. If land development policies and population increase trends remain unchanged, the trend could be extrapolated into the future. In Miami there was a 4% and 2% decline in tree canopy and open space respectively. Tree loss was apparent in two locations: in District 2, along the coast line and at the northern tip of Virginia Key, and along the western edge of District 1. There was very little change in urban areas; not surprising since the city was built out prior to Miami lost $4,000 in annual air pollution removal and 600 tons of carbon storage and 5lbs. of annual carbon sequestration. Stormwater values using BMP values could not be calculated at this scale Citrus Tree loss due to Citrus Canker This map represents data provided by the Florida Department of Agriculture. It represents the incidence of citrus tree removal during the state eradication program. The Landsat data is too coarse to pick up individual incidences of tree loss. However, tree loss due to citrus canker was included in the finer, high resolution data, see page 7. 13

14 American Forests classified Landsat TM 30 meter pixel satellite images from 1996 and 2006 to show the change in landcover inside the Urban Development Boundary line. Tree loss occurred primarily in the western perimeter of the County within the UDB as indicated in red in the graphic. The pattern of tree loss is most likely the result of development. The loss of tree canopy in Miami appeared to concentrate in three locations, in City District 2 along the coast and in District 1, along the western border where exotic vegetation removal occurred. There was very little change in the s urban areas; not surprising since the city was built out prior to

15 American Forests Report Recommendations In summary, this project has quantified the loss of the City of Miami and Miami-Dade County s green infrastructure within the Urban Development Boundary line. The loss, measured over a ten year and a recent two year period, primarily appears due to development and is exacerbated by hurricanes and citrus canker eradication. As the County and City plan for the future, American Forests recommends that the data and CITYgreen software provided with this project be used to run landcover scenarios, establish Countywide tree canopy goals, quantify the progress made with current and new tree initiatives, and educate the public about the value of protecting and enhancing green infrastructure. Use the green data layer and CITYgreen to document the ecosystem services in fulfilling Countywide strategies to protect environmental quality. Share the green data layer provided with this project with County departments and local municipalities Use the modeling capabilities of CITYgreen software for planning. Test the impacts of changing tree canopy, impervious surfaces, and other land covers under different development scenarios. For example, in County District 1, we calculated the stormwater benefits of increasing tree canopy in hurricane-damaged areas. District 1 residential land was modeled so that tree canopy increased from 16% to 25%, replacing open space. Using BMP values of $7/cu. ft the additional tree canopy provided 17 million cu. ft of natural stormwater retention, valued at $119 million savings. In commercial and industrial areas of District 1, we increased tree canopy from 4.6% to 10%. Using $11/cu. ft., additional tree canopy provided 437,000 cu. ft of natural stormwater retention valued at $4.8 million savings. Establish Tree Cover Goals Establish an overall tree canopy goal for Miami-Dade County and. Establish goals for specific land use categories. These goals are based on achieving environmental requirements for air and water. Incorporate these goals into planning policies and test achieving them with the UEA process. Maintain those targets as the County develops over time. Use American Forests canopy goals as a guide, but the County and City should develop its own goals and timeframe to meet the needs of their unique community. 40% tree canopy countywide 50% tree canopy in suburban residential 25% tree canopy in urban residential 10-15% tree canopy in the urban core; greater in areas adjacent to waterbodies. Local communities should adopt countywide goals to be consistent across political boundaries. A lack of consistency would make local compliance of achieving tree canopy goals very difficult. Use the green data layer and CITYgreen to document the ecosystem services provided by existing tree programs and new strategies to protect environmental quality. Share the green data layer provided with this project with County departments and local municipalities Use the modeling capabilities of CITYgreen software for planning. Test the impacts of changing tree canopy, impervious surfaces, and other land covers under different development scenarios. Increase public awareness of the direct relationship between environmental quality and tree canopy. Use analysis findings in popular media to demonstrate and educate the public about the importance of conserving and enhancing the urban forest. Incorporate CITYgreen schools program into public schools to increase awareness of environmental issues, by teaching practical applications of GIS, math, science and geography. Curriculum is available through American Forests. About the Urban Ecosystem Analysis American Forests Urban Ecosystem Analysis is based on the assessment of ecological structures unique combinations of land use and land cover patterns. Each combination performs ecological functions differently and is therefore assigned a different value. For example, a site with heavy tree canopy provides more stormwater reduction benefits than one with lighter tree canopy and more impervious surface. Data Used For the temporal change analysis, landcover was derived from the Landsat 30 meter pixel resolution imagery. The 1996 Landcover was derived from NOAA s Coastal Change Analysis Program, which is a refinement of the 1992 National Land Cover Database from 30 meter LANDSAT imagery and produced by the Multi-Resolution Land Characteristics Consortium. See for more information. The landcover was divided into five categories (water, trees, urban, open space, and bare soil). The 2006 Landcover was derived from 30 meter LANDSAT imagery acquired for Miami- Dade County. It was classified using the Anderson Level 1 classification scheme using a pixel-based classification methodology and See5 statistical modeling and CART tools. 15

16 The South Florida Water Management District provided the 2004 color 1 meter infrared imagery taken between November 2004 and February 2005 with an ADS 40 digital camera. The 2006 imagery was provided by Miami-Dade County with a CIR imagery collect in March. The imagery was resampled to 1 meter to match the earlier imagery resolution. The late date imagery, taken in March 2006 is CIR imagery resampled to 1 meter to match the early date imagery. This imagery was provided by Miami-Dade County. It was classified using the Anderson Level 1 classification scheme using a pixelbased classification methodology and See5 statistical modeling and CART tools. The landcover was divided into five categories (water, trees, impervious, open space, and bare soil). Analysis Formulas Urban Ecosystem Analyses were conducted using CITYgreen software. CITYgreen for ArcGIS used the raster data land cover classification from the high-resolution imagery for the analysis. To comply with the ecology of their landcover characteristics, wetlands were classified as water when calculating stormwater runoff and were classified as a particular landcover (trees, openspace, water, or bare soil) when calculating air quality and carbon benefits. The following formulas are incorporated into CITYgreen software. TR-55 for Stormwater Runoff: The stormwater runoff calculations incorporate volume of runoff formulas from the Urban Hydrology of Small Watersheds model, (TR-55) developed by the US Natural Resources Conservation Service (NRCS), formerly known as the US Soil Conservation Service. Don Woodward, P.E., a hydrologic engineer with NRCS, customized the formulas to determine the benefits of trees and other urban vegetation with respect to stormwater management. For greater accuracy, a stormwater analysis was conducted for each Planning District and then values were added together to provide stormwater runoff for the entire city. L-THIA for Water Quality: Using values from the U.S. Environmental Protection Agency (EPA) and Purdue University s Long-Term Hydrological Impact Assessment (L- THIA) spreadsheet water quality model, The Natural Resources Conservation Service (NRCS) developed the CITYgreen water quality model. This model estimates the change in the concentration of the pollutants in runoff during a typical storm event given the change in the land cover from existing trees to a no tree condition. This model estimates the event mean concentrations of nitrogen, phosphorus, suspended solids, zinc, lead, copper, cadmium, chromium, chemical oxygen demand (COD), and biological oxygen demand (BOD). Pollutant values are shown as a percentage of change. UFORE Model for Air Pollution: CITYgreen uses formulas from a model developed by David Nowak, PhD, of the USDA Forest Service. The model estimates how many pounds of ozone, sulfur dioxide, nitrogen dioxide, and carbon monoxide are deposited in tree canopies as well as the amount of carbon sequestered. The urban forest effects (UFORE) model is based on data collected in 55 U.S. cities. Dollar values for air pollutants are based on averaging the externality costs set by the State Public Service Commission in each state. Externality costs, are the indirect costs to society, such as rising health care expenditures as a result of air pollutants detrimental effects on human health. Acknowledgements for this Study We gratefully acknowledge the funding support provided by Miami-Dade County, the, and Urban and Community Forestry grant funds received through the State of Florida Division of Forestry. We appreciate the information provided by the Florida Department of Agriculture and the South Florida Water Management District in conducting this study. For More Information American Forests, founded in 1875, is the oldest national nonprofit citizen conservation organization. Its three centers Global ReLeaf, Urban Ecosystem Center, and Forest Policy Center mobilize people to improve the environment by planting and caring for trees. American Forests CITYgreen software provides individuals, organizations, and agencies with a powerful tool to evaluate development and restoration strategies and impacts on urban ecosystems. American Forests offers regional training, teacher workshops and technical support for CITYgreen and is a certified ESRI developer and reseller of ArcView and ArcGIS products. American Forests, P.O. Box 2000, Washington D.C Phone: 202/ ; Fax: 202/ ; Web: