K. Bruce Jones1, Kurt H. Riitters2; 5, James D. Wickham2, Roger D. Tankersley Jr.3,

Robert V. O'Neill4, Deborah J. Chaloud1, Elizabeth R. Smith2, and Anne C. Neale1

1 Environmental Sciences Division, U.S. Environmental Protection Agency,Las Vegas, Nevada

2 Environmental Research Center, Tennessee Valley Authority,Historic Forestry Building, Norris, Tennessee

3 Department of Geography, University of Tennessee, Knoxville, Tennessee

4 Environmental Sciences Division, U.S. Department of Energy,Oak Ridge National Laboratory, Oak Ridge, Tennessee

5 Currently: Biological Resources Division, U.S. Geological Survey,Knoxville, Tennessee

An Ecological Assessmentof the United StatesMid-Atlantic Region:

A Landscape Atlas

Dedication

This Atlas is dedicated to our friend and colleague Mason J. Hewitt, whose leadership and inspira-

tion made many of the landscape analyses and displays used in this atlas possible. Mason

pioneered and laid much of the foundation for Geographic Information System applications in the

EPA. He made it possible for many government agencies to use and apply indicators highlighted

in this atlas. Mason also contributed substantially to the education of many young people through

the Boy Scouts of America, teaching young people how to respect and live in harmony with their

natural environment. Mason’s impact on the conservation of our environment will be felt for years

to come, but his kindness, leadership, and vision will be sorely missed.

Table Of Contents

Chapter 1. Taking a Broader View 1

Purpose and Organization of This Atlas 2Landscape Ecology and the Analysis of Broad�ScaleEnvironmental Condition 3How Can Landscape Indicators Help Us UnderstandEnvironmental Conditions? 4How Were the Landscape Indicators Selected? 6How Were the Landscape Indicators Measured? 10How Were the Landscape Indicators Summarized? 14How to Read the Maps and Charts in this Atlas 15

Chapter 2. The National Context 17

Data Sources 17Human Use Patterns 20Forest Patterns 22Patterns Affecting Water Quality 26National Context Summary 28

Chapter 3. The Mid�Atlantic Region 31

Biophysical Setting of the Mid�Atlantic Region 31Humans in Landscapes in the Mid�Atlantic Region 38Water 49Riparian Indicators 49Watershed Indicators 52Forests 60Landscape Change (1970-1990) 67

Chapter 4. A Comparative Assessment of Mid�Atlantic Watershed Conditions 77

Acknowledgements 87

Glossary 89

Appendix. Additional Information About the Indicators in Chapter 3 91

Suggested Further Reading 103

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 1

Environmental quality affects our health, our quality oflife, the sustainability of our economies, and the futuresof our children. Yet pressures from an increasing popula-tion coupled with the need for economic developmentand an improved standard of living often have multipleeffects on our natural resources. So just as a personwith a less-than-healthy lifestyle is more prone to infec-tion, a weakened ecosystem is more vulnerable toadditional stress. Unfortunately, it is often difficult to seethese changes in environmental quality because theyoccur slowly or at scales we do not normally consider.

There is growing public, legal, and scientific awarenessthat broader�scale views are important when assessingregional environmental quality. In the past, media atten-tion has concentrated on dramatic events, focusing ourenvironmental awareness on local or isolated phenom-ena such as cleaning up Superfund sites, stoppingpollution from a drainage pipe, saving individual endan-gered species, or choosing a site for a county landfill. Inan era of environmental regulations, measures of envi-ronmental quality were based on legal standards, likethose for drinking water or air quality. As a result theyreflected a limited view of the environment and themultiple factors that contribute to environmental prob-lems. In response, scientists studied fine�scale modelsystems and often considered humans to be externalfactors. Today, our perceptions are changing. Werealize that humans and our actions are an integral partof the global ecosystem, and that the environment iscomplicated and interconnected with human activitiesacross local and regional scales. We have begun to takea broader view of the world and of our place in naturalsystems.

Technological advancements have made it easier toobtain new views of overall environmental quality. Com-puters and satellites allow us to study larger patterns andprocesses. Combined with a better understanding ofhow the pieces fit together, these technologies help us toassess where we are now with regard to environmentalquality, to envision where we hope to be in the future,and to identify the steps we need to take. This atlastakes advantage of these advanced technologies inassessing environmental condition over the mid�Atlanticregion of the United States.

Just as we now watch broad�scale weather patterns toget an idea of whether it will rain in the next few days, wecan develop a better assessment of current environmen-tal condition by combining regional and local�scaleinformation. Broad�scale weather patterns are importantbecause they affect and constrain what happens locallyon any given day. By taking a broader view of the envi-ronment, or widening our perspective about how theenvironment is put together, it becomes easier to seewhere changes occur and to anticipate future problemsbefore they materialize.

The Chesapeake Bay Program is one of the groups which helped to identify theenvironmental issues of concern in the mid–Atlantic region. The ChesapeakeBay watershed covers a large portion of the area considered in this atlas.

In the past, public and legal attention has been focused on site–specificenvironmental problems such as what is coming out of individual drainage pipes.

Chapter 1: Taking a Broader View

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 12

Purpose and Organization of this Atlas

This atlas is an environmental assessment of the mid�Atlantic region of the United States (Figure 1.1). Theassessment was done using measurements derived fromsatellite imagery and spatial data bases. The informationpresented in this atlas is intended to help the readervisualize and understand the changing conditions acrossthe region, and how the pattern of conditions can beused as a context for community�level situations. Thisatlas does not provide site�specific analyses of smallareas such as individual woodlots. This atlas was devel-oped as part of the Environmental Monitoring and As-sessment Program (EMAP), and is part of a larger,multi-organizational effort to assess environmentalcondition in the mid-Atlantic Region.

The atlas is divided into four chapters with oneappendix. This chapter introduces the reasonsfor doing a broad�scale regional analysis ofenvironmental condition.

Chapter 2 places the mid�Atlantic region intothe context of the lower 48 states. In Chapter 3,the landscape conditions in the mid�Atlantic region areanalyzed and interpreted in terms of a set of ecologicalindicators, summarized by watersheds within the region.Chapter 4 summarizes the overall picture painted bythese landscape indicators and compares relative condi-tions among watersheds in the region. The Appendixprovides methodological information which is not inChapter 3, and has a listing of all indicator scores forevery watershed in the mid�Atlantic region.

Figure 1.1.

The mid–Atlantic region.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 3

Landscape Ecology and the Analysis ofBroad–Scale Environmental Condition

To most people, the term �landscape� suggests either ascenic vista or a backyard improvement project. Toecologists and other environmental scientists, a land-scape is a conceptual unit for the study of spatialpatterns in the physical environment and the influence ofthese patterns on important environmental resources.Landscape ecology is different from traditional ecology inseveral ways. First, it takes into account the spatialarrangements of the components or elements that makeup the environment. Second, it recognizes that therelationships between ecological patterns and processeschange with the scale of observation. Finally, landscapeecology includes both humans and their activities as anintegral part of the environment.

There are many applications for landscape ecology andbroad�scale information in regional assessments. Forexample, we can identify the areas that are most heavilyimpacted today by combining information on populationdensity, roads, land cover, and air quality. In the mid�Atlantic region, we already have good information (fromthe U.S. Census Bureau) about which counties are mosturbanized. But which counties have only a small propor-tion of adjacent forest cover along the stream length?Which counties are character-ized by a high degree offorest fragmentation? Whatabout information for water-sheds instead of counties?Broad�scale measurementscan be taken in order tomake relative comparisons ofthese indicators over theentire region. Broad�scaledata can also help in identify-ing the most vulnerable areaswithin the region. Vulnerable

areas are not yet heavily impacted, but because of theircircumstances they are in danger of becoming so. Oneexample might be a watershed that has a relatively highpercent of forest cover, but is also experiencing rapidpopulation gains. Such an area might be more vulner-able to forest fragmentation than a similar area with lesspopulation or less forest area.

The ability to place localities into a regional context isanother benefit of this approach. Some individual citiesand neighborhoods in the mid�Atlantic Region may seemisolated, perhaps within a large forested area. However,all are connected by physical features and by ecologicalprocesses. Water flows from one place to another, roadsprovide a connecting infrastructure, and land coverpatterns of forest and agriculture form a connectedbackdrop for all of our activities. While land managementdecisions are made and implemented at a local scale, aregional perspective can guide our decisions and makeus better stewards of our environment. By placing ourhomes, neighborhoods, and government organizationsinto a regional landscape picture, we can begin to makeinformed decisions that consider not only our goals andactions, but our neighbors' as well.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 14

Figure 1.2 illustrates how a single community is linked tothe landscape at several different scales and acrossdifferent mapping units (watersheds and counties in thisexample). A small city is highlighted in the middle of thefigure. At this scale we concentrate on individual landparcels and roads, and our decisions are based on alocal perspective. Broader�scale perspectives emergeas we follow the lines up either side of the figure. Wesee that the community is part of both a watershed (left)and a county (right), which, in turn, are components ofgroups of watersheds and counties. These larger groupsare components of the entire region.

How Can Landscape Indicators Help UsUnderstand Environmental Conditions?

An indicator is a value calculated by statistically combin-ing and summarizing relevant data. Well�knowneconomic indicators include the seasonally�adjustedunemployment percentage and number of housing starts,both of which indicate overall economic condition. Inthese indicators, seasonal adjustment is made with amodel, and most economists look at several indicatorstogether instead of just one at a time. Similarly, land-scape indicators can be measurements of ecosystemcomponents (such as the amount of forest) or processes(such as net primary productivity), and modeled adjust-ments can be used to help interpret the measurements inorder to understand overall ecological conditions.

Figure 1.2.

This atlas may help to understand how acity (bottom center) fits into a largercontext of either watersheds (leftbranch) or counties (right branch).

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 5

Figure 1.3.

Spatial patterns of land cover inrelation to streams for a county in themid–Atlantic region. Stream segmentsare colored green, yellow, or red,depending on whether the segmentsare adjacent to forest, agriculture, orurban land cover.

Figure 1.3 shows an example of measuring spatialpatterns as an indicator of stream conditions. Thedistribution of streamside land cover has been mappedfor the same county that was shown in Figure 1.2.Stream segments that are green have adjacent forest,and segments that are yellow and red have adjacentagriculture and urban land cover, respectively. Thepattern of streams in relation to land cover is an indicatorof conditions within the stream. Forests filter pollutants,

preventing them from reaching the water, whereasagriculture and urban land often contribute pollutants tostreams. A simple summary indicator might be thepercentage of stream length in the county that is adjacentto forest land cover. To refine this indicator, a modelmight help to account for �natural� conditions, for examplewhether or not forest was the natural land cover for thecounty.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 16

RecoveryLarge-scaledisturbance

(fire or flood)

Large-scaledisturbance

(fire or flood)

Time

Populationpersists

Populationdoes notpersist

How Were the Landscape Indicators Selected?

As a starting point for selecting indicators, we consideredwhat people in the region said they cared about. Forexample, concern for wildlife populations provides areason to examine indicators of habitat fragmentation.Fragmentation of natural habitats can severely affectanimal populations, as shown by the conceptual modelillustrated in Figure 1.4. Concerns from the mid�Atlanticwere then matched to our ability to take meaningfulmeasurements, recognizing that some things just can�tbe measured very well given the available data or mod-els. As a result of workshops and advice from people in

Figure 1.4.

Habitat fragmentation can result in the loss of a species due to natural distur-bance. In this example larger, more connected habitat sustains the species overtime, whereas smaller, more isolated habitat loses the species over time.(In this example, tan is non-habitat, red is occupied habitat, and white isunoccupied habitat.)

the mid�Atlantic region, four general environmentalthemes were identified � people, water, forests, andlandscape change. Figures 1.5 and 1.6 are pictorialrepresentations of key landscape attributes that affect thesustainability of environmental condition across broadscales. Figure 1.5 shows some key landscape compo-nents that sustain a high quality environment, and Figure1.6 shows some human modifications of the landscapethat can reduce the sustainability of natural resources.These illustrations represent some of the importantlandscape indicators analyzed in this atlas.

Populationpersists

Populationdoes notpersist

Large-scaledisturbance(fire or flood)

RecoveryLarge-scaledisturbance(fire or flood)

Time

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 7

Figure 1.5.

A pictorial representation of somelandscape components that sustaina high–quality environment.

Large blocks ofinterior foresthabitat areimportant formany forestspecies

Riparian zonesfilter sedimentsand pollutants,especially inagriculturalareas, inaddition toprovidingimportantwildlife habitats

Forest connectivityis crucial for thepersistance offorest species,especially in areaswith moderateamounts ofagriculture

Forest edgehabitat is

important formany species

that require morethan one habitat

type to survive

The number offorest scales

surrounding apoint in thelandscape

determines thevariety of

forest speciesfound there

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 18

Agriculture areas nearstreams increase stream

sediment loads andchemical inputs

Dams alter the naturalhabitats and hydrology

of streams

Agriculture on steepslopes increases soilloss and sedimentloading to streams

The amount andlocation of agriculturein a watershedinfluenceslandscape patternFigure 1.6

A pictorial representation of some humanmodifications of the landscape that reduce thesustainability of natural resources

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 9

Air pollution spreadsacross the landscape,

affecting regionalair quality

Humans reduce ripariancover along streams,which decreasesfiltering capacity

Forest harvestpractices influenceforest connectivityand patch sizes

Population growthresults in loss of forestand changes in overallwatershed landscapepattern

Roads near streamsincrease sediment andpollution loads byincreasing surfacerunoff off

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 110

The indicators reported in this atlas are not appropriatefor addressing some kinds of questions. For example,they are not intended to assess conditions for very smallareas. The goal was to develop a consistent and com-prehensive look at the entire region, and there weretrade�offs between the level of detail and the size of thearea that could be considered. Future work would lookat smaller areas using more detailed data sets. Theregional perspective would be a valuable guide to deter-mine where this additional expense might be warranted.The indicators reported here were not evaluated inabsolute terms; only relative comparisons were made. Inorder to set absolute standards like the ones which existfor drinking water and air pollution, the system musteither be very simple or intensively studied to providevery detailed scientific information. Regional ecosystemsare simply too complicated to set absolute standardsusing our current technology and understanding.

Landscapes are very complicated, and the generality ofthe conceptual models is an accurate reflection of levelof scientific understanding concerning landscape dynam-ics. Scientists who study landscape ecology are trying toimprove our ability to interpret landscape indicatorsrelative to environmental values. The improvements willhelp to interpret the information that is contained in thisatlas and may suggest new landscape indicators that wehave not considered. In the meantime, it is worth explor-ing how much is known about regional environmentalconditions and what conclusions can be made usingstate of the art landscape indicators.

How Were the Landscape Indicators Measured?

Many kinds of data were used to prepare the indicatorsshown in this atlas. Federal agencies were the primarysource for data, including maps of elevation, watershedboundaries, road and river locations, population, soils,land cover, and air pollution. Sources included the U.S.Geological Survey (USGS), the U.S. EnvironmentalProtection Agency (USEPA), the U.S. Department ofAgriculture (USDA), the U.S. Census Bureau, and theMulti�Resolution Land Characteristics Consortium(MRLC).

Data collected by satellites were used to map land coverand its change over time. The sensors carried on satel-lites measure the light reflected from the Earth�s surface.Because different surfaces reflect different amounts oflight at various wavelengths, it is possible to identify landcover from satellite measurements of reflected light.Figure 1.7 illustrates the differential reflectance propertiesof water, sediments suspended in water, and land sur-faces for a typical satellite image. Examples of landcover maps derived from satellite images appear later inthis atlas.

In a typical digital map, data are stored as a series ofnumbers for each map. These maps can be thought ofas checkerboards, where each grid square (or pixel,which is an abbreviation of �picture element�) representsa data value for a particular landscape attribute (forexample soils, topography, or land cover type) at aspecific location.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 11

Figure 1.7.

Illustration of differential lightreflectance properties forwater, sediments suspendedin water, and land surfacesover a portion of easternVirginia and the ChesapeakeBay. These images can bemanipulated in various waysto extract information aboutthe Earth’s surface.Source: North American

LandscapeCharacterizationProgram

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 112

Several techniques are used to take a measurement of alandscape indicator. One method (�overlaying�) simplyexamines maps of different themes in order to extractinformation about spatial relationships among the themes(Figure 1.8). For example, by overlaying maps of landcover and topography, we can look at the occurrence ofagriculture on steep slopes. These relationships are thenstored as a new map which combines the informationfrom the original set of maps. Another method (�spatialfiltering�) can be thought of as using a �sliding window� to

Land cover (with agriculture in red) is combined with topography toindicate agriculture on steep slopes. The combined map showsagriculture on slopes greater than 3%.

Figure 1.8.

Example of overlaying digital maps to produce a new map of an indicator.

calculate indicator values within small areas that are partof a larger map (Figure 1.9). Spatial filtering is used hereto create surface maps of indicator values; these surfacemaps help us to visualize the spatial pattern of indicatorsin more detail than is provided by the watershed�levelsummaries described in the following section.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 13

Original landcover data:

Resulting, spatiallyfiltered data:

Step 1 Step 2 Step 3

Legend for Filtered Coverage

In this example of the spatial filtering process, a 3 pixel by 3 pixelwindow (outlined in red - top row of figures) is used to map landcover diversity. In step 1, there are 2 cover types in the windowwhich maps to a single blue pixel at the center of the window. Instep 2, the window slides over one pixel. There are 3 cover typesin the new window, mapping to a single green pixel in the center ofthe window. In step 3, the window again slides over one pixel. Thethird window includes 3 cover types and maps again to a singlegreen pixel.

Figure 1.9.

Illustration of spatial filtering which creates a surface map.

One Cover Type

Two Cover Types

Three Cover Types

Four Cover Types

More Than Four Cover Types

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 114

How Were the Landscape Indicators Summarized?

This atlas uses watersheds, as defined by USGS hydro-logic accounting units, to summarize landscape indicatorvalues (Figure 1.10). Roughly speaking, hydrologicaccounting units follow watershed boundaries. In manyecological studies, especially those which assess water�related concerns, watersheds are an appropriate unit forsummarizing data. A watershed is defined as an area ofland that is drained by a single stream, river, lake, orother body of water. The dividing lines between water-sheds are formed by ridges. Water on one side flowsinto one stream, while water on the other side may flowinto a different stream. Thus, watersheds are a naturalunit defined by the landscape. Strictly speaking, theUSGS hydrologic accounting units are not watersheds inthe classical sense of a topographically�defined catch-ment area. They are used in this atlas because they aregenerally accepted and consistent across the entirenation.

To determine relative condition, the watersheds wereranked by the values for a given indicator, from highest tolowest, and then were divided into five groups. Eachgroup had an equal number of watersheds; at the na-tional scale (Chapter 2) there were approximately 425watersheds in each group. At the mid�Atlantic regionalscale (Chapters 3 and 4) there were 25 watersheds ineach group. All watersheds within the same group werecolored with one of five colors, using green to representmore-desirable conditions and red to represent less-desirable conditions. Maps based on rankings are usefulfor comparing relative conditions, but they do not conveythe actual values of the indicators. That information issummarized in the companion bar charts which show thenumber of watersheds with different indicator values. Bylooking at the map and bar chart together, it is possible toestimate the ranges of indicator values associated with agiven watershed group.

To calculate indicatorvalues for a watershed,the watershed boundary isoverlayed on a GIScoverage. Information forthat watershed is then cutout from the largerdataset.

Figure 1.10.

Illustration of the cookie–cutterprocess that was used tosummarize information bywatershed.

As a practical matter, the authors of this atlas madejudgment calls when assigning �red� and �green� colors tothe maps, and �more desirable� and �less desirable�interpretations to the indicator values. For example,forest edge was colored �green� and interpreted as �moredesirable� when its values were high because the mea-surement was included as an indicator of a type ofhabitat. Similar judgment calls were made for otherindicators. Higher values for the vegetation-increaseindicator were considered to be a negative impact be-cause much of this change did not represent restorationof the potential natural vegetation, but rather was morestrongly associated with human activities. One of theadvantages of presenting indicator scores for all water-sheds (see Appendix) is that any reader can simplyredefine the color scheme and make new judg-ments based on other criteria.

An Ecological Assessment of the United States Mid-Atlantic Region: Chapter 1 15

Woody landcover along streams was calculated as the percentof streamlength with forest landcover types. By intersecting abuffer zone around each stream with the landcover, a dataset iscreated which records all landcover types within a specifieddistance to stream center.Sources: USGS 1:100,000 River Reach 3 stream data, andMRLC 30 meter Landsat land-cover data.

Indicator Value

Num

ber o

fW

ater

shed

s

The value shown on the X axis is the upper limit of adata range. For example, this bar shows the numberof watersheds with data values between 60-70.

Quintile Data Range (Percent)

1 <70.600

2 70.600 - 76.869

3 76.870 - 84.579

4 84.580 - 89.889

5 >89.890

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 00

2 0

4 0

1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

20

40

10 20 30 40 50 60 70 80 90 100

The Data Rangeshows theindicator valuesfor watershedscontained ineach quintile.

A brief explanation of the essential methods is given.Details are in the Appendix.

The map of mid-Atlantic watersheds is color-codedto show relative conditions among watersheds. Thecolors range from red to green, indicating rela-tively “less desirable” and “more desirable”conditions, respectively.

Figure 1.11.

How to read the maps and charts in this atlas.

How to Read the Maps and Charts in this Atlas

Figure 1.11 illustrates the types of maps and charts thatappear in Chapters 2 and 3, with some description oftheir various elements. It may be useful to bookmarkthis page for later reference.

A quintilecontains 1/5 ofthe watersheds.Quintiles areformed afterrankingwatersheds forthe indicator.

0