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Appalachian National Scenic Trail Landscape Change Summary

Figure 1. The Appalachian National Scenic Trail showing population density of locations within 150 miles
Figure 1. The Appalachian National Scenic Trail showing population density of locations within 150 miles. Cross-hatching identifies ecoregional subsections with higher than average (x̄) % converted land, while darker orange shading corresponds to higher population density. Topographic background prepared by ESRI ArcGIS Online and data partners including USGS and ©2007 National Geographic Society, and population density by ©2013 Esri

Introduction

Landscape alteration may be one of the most lasting effects humans have had on the environment. When roads are constructed, homes are built, and businesses expanded, habitat may be altered to become unsuitable or too fragmented to sustain native species. In the Northeast, most ecosystems have experienced loss and fragmentation of habitat, and these changes are a threat to native biodiversity, can influence the behavior of invasive species, or degrade water quality. For these and other reasons, park managers need information about changes to the landscape both inside and outside the Appalachian National Scenic Trail (APPA) to effectively conserve APPA's native flora and fauna. Land use and landscape change, sometimes referred to as landscape dynamics, is such a key concern for managers that it was identified as one of APPA's twelve vital signs (Shriver Et Al. 2005; Dieffenbach 2011).

Widespread clearing for agriculture and logging for timber have left very few terrestrial systems in the eastern United States untouched. The APPA itself threads through some of the most remote areas in the east, but it is also very close to some of the most densely settled areas within the United States. Within 241 kilometers (150 miles) of the APPA, there are 115 cities with populations greater than 50,000 and approximately 15-20% of the entire United States population lives within this area (Figure 1). Consequently, the APPA corridor represents a vital north-south connection between otherwise fragmented forests in this region. In comparison to the watersheds immediately surrounding the APPA—defined by USGS 10-digit hydrologic unit codes (Figure 1)—the corridor and surrounding land base contains more forested land (92% versus 67%), and less developed and agricultural land (3% versus 9% and 2% versus 20%, respectively). A large and growing body of scientific literature documents the negative impacts of habitat fragmentation on biodiversity in a wide variety of ecological systems (Fahrig 2003), and the APPA may be an important part of any regional effort to address fragmentation. The impacts of fragmentation have been especially well documented upon avian communities, and population declines of a variety of forest interior avian species are linked to habitat fragmentation (Rich Et Al. 1994, Austen Et Al. 2001). So, while APPA offers a sanctuary for native flora and fauna throughout its length, its proximity to development poses many complications for resource managers who seek to minimize the effects of landscape change.

Table 1. Subsections that intersect the Appalachian National Scenic Trail (North to South). Percent that is APPA land is that portion of the subsection occupied by lands administered as part of the Appalachian National Scenic Trail. Percent of APPA that is Protected is that portion of APPA Land that is GAP status 1 or 2.

The first step in understanding landscape dynamics is to characterize the existing landscape within and around APPA and, if possible, determine how ecosystems have changed over time. In 2009 the National Park Service's NPScape program released a series of reports that described conditions around parks, including APPA (Story et.al.). The work by the NPScape program made it possible to begin to appreciate the extent to which lands immediately surrounding the footpath have changed.

On a tangential matter, understanding large-scale landscape alteration is a key component of predicting and understanding the occurrence and behavior of fire, and was the motivation for the development of a series of tools (Barrett 2006) that attempt to describe the difference between historic vegetation communities and communities that now exist on the same landscape. While the tools were developed with fire management in mind, they are equally valuable for understanding general ecological health, and made it possible to complete the analysis outlined below. When used in combination with remotely sensed data, the tools give resource managers the ability to compare historic conditions with those that exist today and make assessments on the condition of those resources (Hoekstra Et Al. 2004; Svancara Et Al. 2009a; Swaty Et Al. 2011).

Hoekstra (2004) developed a measure called the Conservation Risk Index (CRI) that attempts to identify areas at greatest risk due to habitat loss. CRI is the ratio of converted land to protected land, with converted land being defined as areas converted to agricultural and managed areas, as well as artificial surfaces. Protected lands are lands that have a GAP management status of 1 or 2, as defined by Edwards (1993). GAP status 1 is defined to be "an area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a natural state within which disturbance events (of natural type, frequency, intensity, and legacy) are allowed to proceed without interference or are mimicked through management," while GAP Status 2 is defined to be "an area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a primarily natural state, but which may receive uses or management practices that degrade the quality of existing natural communities, including suppression of natural disturbance" (USGS 2012).

The work by Swaty Et Al. (2011) builds upon the CRI process by incorporating a measure of alteration that takes into consideration how current conditions depart from historic conditions. Swaty's revision attempts to account for alterations to communities that have not transformed the landscape from "natural" to "converted," but have nonetheless impacted the landscape in a significant way. For example, lands that have been impacted by logging are not considered converted when a CRI is calculated, but are incorporated into the process developed by Swaty. The revised process developed by Swaty is known as the Ecological Conservation Risk Index (ECRI).

The information presented on this page focuses on 20 ecoregional subsections (Table 1) that are within the HUC10 shell (Figure 1). The HUC10 shell contains 50 subsections, but only 20 directly intersect lands administered as part of the APPA. The portion of each subsection that is occupied by the APPA ranges from <0.01% (of the total land area of a subsection within the HUC10 shell) to 3.05% (Table 1).

Methods

Data from the NPS NPScape program and LandFire (http://www.landfire.gov/) were combined with methods described by Hoekstra Et Al. (2004), Svancara Et Al. (2009a), Svancara (2009b), and Swaty Et Al. (2011) to calculate CRI and ECRI values (table 2). All datasets were "cut" to fit the APPA HUC10 shell. The HUC10 shell, or the general frame of reference used to establish an area of interest around the APPA, is the "outer" boundary of all HUC10 hydrologic units that are within 5 miles of the APPA land base. The HUC10 shell is based on watersheds defined by the USGS at the fifth level of the Hydrologic Unit Code system, with each being given a discrete 10-digit code (HUC10). The hydrologic unit system was developed by the USGS and subsequently modified by the Natural Resource Conservation Service (NRCS). There are 177 individual HUC10 hydrologic units within this shell. Though they are termed watersheds, Omernik (2003) explains that hydrologic units are not always true watersheds and that some hydrologic elements contained within the HUC10 shell may not include all upstream components of a true watershed. However, for the purpose of defining an area of interest around the APPA we believe the hydrologic unit system is satisfactory.

After cutting datasets to match the HUC10 shell, datasets were subsequently associated with the corresponding ecoregional subsection.

Natural versus converted land and protected area data (PAD) available from NPScape were used to generate CRI values and to generate an ecosystem risk assessment. CRI is the ratio of converted land to protected land, with protected land being land with a GAP status of 1 or 2 (Edwards 1993; Svancara Et Al. 2009c).

CRI = % Converted Lands / % Protected Lands

Hoekstra Et Al. (2005) classifies lands into "Status Categories" in the following way:

  • ≤ 20% Converted Land OR CRI ≤ 2 = "Less Risk"
  • >20% Converted Land AND CRI > 2 = "Vulnerable"
  • >40% Converted Land AND CRI >10 = "Endangered"
  • >50% Converted Land AND CRI > 24 = "Critically Endangered"

To calculate the ECRI value, additional data were obtained from LandFire and processed using the Fire Regime Condition Class Mapping Tool (FRCCmt). Among the outputs from this tool is an area adjusted summary listing the percent (%) of each subsection that is considered to be highly altered when compared to "pre-European" condition. This measure is combined with the previously calculated CRI value to produce the ECRI.

ECRI = (% Converted Land + % Highly Altered Land) / % Protected Lands

ECRI uses the same thresholds as CRI for Less Risk, Vulnerable, Endangered, and Critically Endangered, but the ECRI calculation incorporates the percent of an area that has been highly altered. So, for each of the subsections the ECRI status categories will naturally shift towards more impacted categories in comparison to the CRI calculations, with some subsections shifting 2 or more entire categories (Table 2). When viewing the results, it is important to understand that land can simultaneously be highly altered and converted. It is equally important to recognize that the total amount of land that is impacted cannot exceed the total amount of available land. To prevent the same lands from being counted twice and thereby eliminate possibility that the sum of highly altered and converted lands might exceed 100% of available land, the process of identifying highly altered lands was only conducted on lands that were not already considered converted.

  • ≤ 20% (% Converted Land + % Highly Altered Land) OR CRI ≤ 2 = "Less Risk"
  • >20% (% Converted Land + % Highly Altered Land) AND CRI > 2 = "Vulnerable"
  • >40% (% Converted Land + % Highly Altered Land) AND CRI >10 = "Endangered"
  • >50% (% Converted Land + % Highly Altered Land) AND CRI > 24 = "Critically Endangered"

Discussion

Based on land area, 15 out of the 20 subsections (75%) through which the APPA passes are more than 50% highly altered, as determined by the LANDFIRE methodology (Barrett Et Al. 2006; Rollins 2009). Overall, the range of highly altered land is 13.93% (Table 2; M221AD, Northern Great Valley) to 75.34% (Table 2; M211Ac, Maine Central Mountains). Areas that are highly altered are defined to be those areas that score 67 or higher on the ecological alteration index (EAI) presented by Barret Et Al. (2006), and are not necessarily areas that have been converted for agricultural or urban purposes. In northern New England, like the Maine Central Mountains where the EAI is the highest among subsections that intersect the APPA, very little land has been converted (0.7%, Table 2) but most of these lands have been altered. In all likelihood, the disturbance mechanism was logging, a common practice in northern New England. Most subsections, particularly those in the mid-Atlantic region, have an abundance of converted lands, with converted lands defined to be those lands that are classified as developed, pasture/hay, or cultivated (Table 2).

Table 2. Appalachian National Scenic Trail Converted Land, CRI, and ECRI Status by Subsection. Click on headings to sort values, Subsection sorts north to south.

Figure 2. The Appalachian National Scenic Trail showing ecosystem alteration by ecoregional subsections following the CRI methodology described by Hoekstra Et Al. (2005; Dark Green = Less Risk; Light Green = Vulnerable; Yellow = Endangered; Red = Critically Endangered). Topographic background prepared by ESRI ArcGIS Online and data partners including USGS and ©2007 National Geographic Society.
Figure 3. The Appalachian National Scenic Trail showing ecosystem alteration by ecoregional subsections following the methodology described by Swaty Et Al. (2011; Dark Green = Less Risk; Light Green = Vulnerable; Yellow = Endangered; Red = Critically Endangered). Topographic background prepared by ESRI ArcGIS Online and data partners including USGS and ©2007 National Geographic Society.

Mean % converted land for the 20 subsections is 23.96%, and Figures 1 and 4 show subsections that are above this level (cross hatched in Figure 1; light blue line in Figure 4). Four of the five subsections with above average % converted lands have an ECRI status of Critically Endangered and the fifth is Endangered, while only 2 of the subsections with below average % converted lands have an ECRI status of Critically Endangered (Table 2). Given that the mean of highly altered land is 52.98%, which is combined with % converted land to calculate an ECRI status, this is not an unexpected result but clearly illustrates the importance of land protection in areas that are highly converted because the presence of protected lands is the only counter-balance to an otherwise highly developed landscape—assuming, of course, that CRI and ECRI are agreable metrics for assessing land use characteristics. APPA can—and does—help to offset some of the landscape alterations, but the APPA portion of each subsection is generally quite small, ranging from <0.01% to 3.05% of each subsection (Table 1) so while the opportunity exists for APPA to contribute in a meaningful way toward land protection, the ability to do may be limited.

Figure 4. Appalachian National Scenic Trail Land Status by Subsection. Bright green = acreage weighted average (x̄) % Conserved Land; light blue = acreage weighted average (x̄) % Converted Land; red = acreage weighted average (x̄) % Highly Altered Land.

In most instances APPA lands are designated as protected land with a GAP status of 1 or 2, but there are portions of the trail where this is not the case. Tables 1 and 2 show that the range of % APPA land that is GAP status 1 or 2 ranges from 0.00% (Northern Piedmont) to 90.05% (White Mountains). For example, Figure 5 shows a segment of trail between West Virginia and New Jersey where the trail approaches and then enters the Northern Ridge and Valley subsection (M221Ac, shown in red). There are few protected areas (Figure 5, GAP Status 1 & 2) in the Northern Ridge and Valley subsection and the same is true for the subsections immediately to its south (M221Ad, Northern Great Valley). The portion of the Northern Ridge and Valley subsection that is GAP status 1 or 2 is only 2.18% of available APPA land area (Tables 1 & 2). Data used to complete this analysis suggest that some portions of the trail in this subsection may not be sufficiently protected to rate a GAP status of 1 or 2, but instead has a GAP status of 3. GAP status 3 lands do provide some land protection but also allow certain "extractive" activities such as logging or mineral removal. Thus, for the purpose of identifying lands that are fully protected, GAP status 3 lands are not typically considered in this kind of analysis. To fully understand these implications, and the land conservation role the APPA can play in the larger landscape, we tested to see how the ECRI status results might differ if we adjusted all APPA lands in the M221Ac subsection to a GAP status of 1 or 2. By adjusting the % protected land by the amount of land occupied in this subsection by trail lands (just 1.32% of total), the status rating for this subsection shifts from Critically Endangered to Endangered. The shift in this instance occurs because the initial ECRI value was close enough to the threshold (24) that the addition of a modest amount of protected land made a difference. Similar adjustments may not necessarily yield similar results in other subsections, however.

In general, the best option to further reduce the potential threat posed by landscape alterations adjacent to APPA is to protect additional land either by acquisition or by enhancing the strength of existing protection. The Northern Ridge and Valley subsection may be a good candidate because the amount of this subsection occupied by APPA is more than average yet the amount of APPA land that is currently GAP status 1 or 2 is low. This assumes that the GAP status designations are correct and that lands on or immediately adjacent to the APPA are not eroneously grouped with other nearby lands with less restrictive management. And, as illustrated above, if the APPA corridor is more stringently protected in this area the result could be an improvement of the status classification a full level from "Critically Endangered" (ECRI) to "Endangered." Another candidate may be the Northern Piedmont subsection (221De). The Northern Piedmont subsection has the least area, by %, of any subsection that directly intersects APPA land (Tables 1 & 2) and also has the highest ECRI score (Table 2) because there is little protected land beyond that offered by APPA. Ordinarily, a subsection that barely intersects the APPA land area might seem to be a poor candidate for land conservation activities, but this subsection parallels the APPA land area boundary for nearly the entire length of this subsection so there appear to be abundant opportunities. While it would take a substantial amount of land protection to reduce the status for this subsection, like demonstrated with the Northern Ridge and Valley subsection (see above) to anything less than Critically Endangered, any land protection efforts in this highly developed area not far from the Washington D.C. area would be beneficial to the health of the resource.

Figure 5. The Appalachian National Scenic Trail through the Northern Ridge and Valley (M221Ac) subsection.
Figure 5. The Appalachian National Scenic Trail through the Northern Ridge and Valley (M221Ac) subsection (shaded red). Topographic background prepared by ESRI ArcGIS Online and data partners including USGS and ©2007 National Geographic Society, and population density by ©2013 Esri

The CRI and ECRI calculations both provide insight and value for resource management, but neither can be considered superior to the other. CRI may underestimate the magnitude of landscape level impacts, while ECRI may overstate those impacts. However, when used in combination it is possible to identify areas that may be in greatest need for stewardship efforts, and where those efforts might be most productive. As discussed above, land protection efforts in subsections where little protections currently exists may be a worthwhile strategy. The Northern Piedmont (221De) was previously mentioned, but the Connecticut Lakes subsection (M211Af) is another subsection where land protection efforts may be well placed, but for slighly different reasons than the Northern Piedmont. The Connecticut Lakes subsection is in Maine, making up some of the most remote portions of the APPA. Land conversion in the Connecticut Lakes is the second least among subsections (Table 2), but the lack of protected land is a concern (tied for least). This subsection is unique among the 20 considered on this page because it's status based on CRI is Less Risk, while the ECRI status is Critically Endangered. No other subsection makes the full status swing from one extreme to the other. The lack of protected land in combination with a long history of landscape alteration by logging is the reason for this dichotomy, and may make this subsection a worthwhile target for land protection efforts.

Only two subsections achieve "Less Risk" status based on both CRI and ECRI calculations, and in both instances they do this based on an abundance of protected land. The White Mountain (M211Ad) and Kittatinny-Shawangunk Ridges (221Bd) subsections include 47.3% and 45.0% of protected land, respectively. The White Mountain subsection includes the White Mountain National Forest, while the Kittatinny-Shawangunk Ridges subsection includes Delaware Water-Gap National Recreation Area. Paradoxically, the White Mountain subsection has the second highest percentage of highly altered land (74.72%), as discussed above, while the Kittatinny-Shawangunk Ridges is among the lower tier of subsections for percentage of highly altered lands (49.82%). In both instances the prevalance of protected land is the reason for the status rating.

In summary, the information presented on this page equips resource managers with information not previously available in a single location. Having the ability to identify lands in close proximity to APPA lands, and their CRI and ECRI status, will help target limited land conservation resources and more effectively identify potential regions for conservation efforts.

Sources cited

Austen, M. J. W., C. M. Francis, D. M. Burke, and M. S. Bradstreet. 2001. Landscape context and fragmentation effects on forest birds in southern Ontario. The Condor 103(4):701-714.

Barrett, S.W., T. DeMeo, J.L. Jones, J.D. Zeiler, and L.C. Hutter, 2006. Assessing Ecological Departure from Reference Conditions with the Fire Regime Condition Class (FRCC) Mapping Tool. In: Andrews, Patricia L., and Butler, B.W., comps. 2006. Fuels Management—How to Measure Success: Conference Proceedings. 28-30 March 2006; Portland, OR. Proceedings RMRS-P-41. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Dieffenbach, F, 2011. Appalachian National Scenic Trail vital signs monitoring plan. Natural Resource Technical Report NPS/NETN/NRR2011/389. National Park Service, Northeast Temperate Network, Woodstock, VT.

Edwards, Thomas C. Jr., J.M. Scott, C.G. Homer, and R.D. Ramsey 1993 Gap analysis: a geographic approach for assessing national biological diversity, Natural Resources and Environmental Issues: Vol. 2, Article 11. Available at: http://digitalcommons.usu.edu/nrei/vol2/iss1/11

Fahrig, L. 2003. Effects of habitat fragmentation on biodiversity. Annual Review of Ecology Evolution and Systematics 34:487-515.

Hoekstra, J.M., T.M. Boucher, T.H. Ricketts, & C. Roberts 2005. Confronting a biome crisis: Global disparities of habitat loss and protection. Ecology Letters, 8, 23-29.

Olson, D.M., E. Dinerstein, E.D. Wikramanayake, N.D. Burgess, G.V.N. Powell, E.C. Underwood, J.A D'Amico, I. Illanga, H.E. Strand, J.C. Morrison, C.J. Louks, T.F. Allnutt, T.H. Ricketts, Y. Kura, J.F. Lamoreux, W.W. Wettengel, P. Hedao, and K.R. Kassem (2001). Terrestrial ecoregions of the World: a new map of life on Earth. BioScience, 51, 933-938.

Omernik, J.M. 2003. The Misuse of Hydrologic Unit Maps for Extrapolation, Reporting, and Ecosystem management. Journal of the American Water Resources Association. (JAWRA) 39(3):563-573.

Rich, A. C., D. S. Dobkin, and L. J. Niles. 1994. Defining forest fragmentation by corridor width: The influence of narrow forest dividing corridors on forest-nesting birds in southern New Jersey. Conservation Biology 8:1109-1121.

Rollins, M.G. 2009. LANDFIRE: A nationally consistent vegetation, wildland fire, and fuel assessment. International Journal of Wildland Fire 18: 235-249.

Shriver, G., T. Maniero, K. Schwarzkopf, D. Lambert, F. Dieffenbach, D. Owen, Y. Q. Wang, J. Nugranad-Marzilli, G. Tierney, C. Reese, T. Moore. November 2005. Appalachian Trail Vital Signs. Technical Report NPS/NER/NRTR--2005/026. National Park Service. Boston, MA.

Story, Mike, L.K. Svancara, T. Curdts, J. Gross, S. McAninch. A Comparison of Available National-Level Land Cover Data for National Park Applications. National Park Service. Available at: http://www.nps.gov/gis/remote_sensing/rss/documents/LandCoverComparison_Report_Final.pdf

Svancara, L. and M. Story. 2009a. Measure Development Summary: Land Cover / Land Use. Office of Inventory, Monitoring, and Evaluation, National Park Service, Fort Collins, Colorado, USA.

Svancara, L. 2009b. Measure Development Summary: Conservation Status. Office of Inventory, Monitoring, and Evaluation, National Park Service, Fort Collins, Colorado, USA.

Svancara, L. K., J. M. Scott, T. R. Loveland, and A. B. Pidgorna. 2009c. Assessing the landscape context and conversion risk of protected areas using satellite data products. Remote Sensing of Environment 113 (2009) 1357-1369.

Swaty R., K. Blankenship, S. Hagen, J. Fargione, J. Smith, J. Patton. 2011. Accounting for Ecosystem Alteration Doubles Estimates of Conservation Risk in the Conterminous United States. PLoS ONE 6(8): e23002. doi:10.1371/journal.pone.0023002

USGS. 2012. National Gap Analysis Program. Available at: http://gapanalysis.usgs.gov/

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