Use of remote sensing techniques to determine the effects of grazing on vegetation cover and dune elevation at Assateague Island National Seashore: impact of horses.
Abstract: The effects of grazing by feral horses on vegetation and dune topography at Assateague Island National Seashore were investigated using color-infrared imagery, lidar surveys, and field measurements. Five pairs of fenced and unfenced plots (300 m2) established in 1993 on sand flats and small dunes with similar elevation, topography, and vegetation cover were used for this study. Color-infrared imagery from 1998 and field measurements from 2001 indicated that there was a significant difference in vegetation cover between the fenced and unfenced plot-pairs over the study period. Fenced plots contained a higher percentage of vegetation cover that was dominated by American beachgrass (Ammophila breviligulata). Lidar surveys from 1997, 1999, and 2000 showed that there were significant differences in elevation and topography between fenced and unfenced plot-pairs. Fenced plots were, on average, 0.63 m higher than unfenced plots, whereas unfenced plots had generally decreased in elevation after establishment in 1993. Results demonstrate that feral horse grazing has had a significant impact on dune formation and has contributed to the erosion of dunes at Assateague Island. The findings suggest that unless the size of the feral horse population is reduced, grazing will continue to foster unnaturally high rates of dune erosion into the future. In order to maintain the natural processes that historically occurred on barrier islands, much larger fenced exclosures would be required to prevent horse grazing.
Publication Date: 2005-01-06 PubMed ID: 15633024DOI: 10.1007/s00267-004-0009-xGoogle Scholar: Lookup
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- Journal Article
Summary
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The research uses remote sensing technology to study the impact of grazing by feral horses on the vegetation and dune structure in Assateague Island National Seashore, concluding that the horses have contributed significantly to dune erosion and affected the vegetation cover.
Study Methodology
- The study was carried out on Assateague Island National Seashore, using five pairs of fenced and unfenced plots. These plots were established in 1993 on sand flats and small dunes, and they had similar elevation, topography, and vegetation cover at the outset.
- The research employed color-infrared imagery, lidar surveys, and field measurements to assess changes in vegetation cover and dune topography over the years.
- Color-infrared imagery was used to distinguish between different types of vegetation based on their reflectance of infrared light. Images taken in 1998, along with field measurements from different years, were compared to assess differences between fenced and unfenced plots.
- Lidar surveys were used to evaluate changes in dune elevation and topography. Measurements were taken in 1997, 1999, and 2000 to assess differences between fenced and unfenced plots over a period of time.
Analysis and Findings
- The analysis revealed significant differences in vegetation cover and dune architecture between the fenced and unfenced plots. The fenced plots had more vegetation cover and were dominated by American beachgrass.
- Additionally, the fenced plots had higher elevations, measuring about 0.63 meters taller on average than the unfenced ones. The heights of the unfenced plots generally decreased after their establishment in 1993.
- These findings strongly suggest that the grazing activities of the feral horses have had a substantial impact on dune formation and erosion on Assateague Island.
Implications and Recommendations
- If the size of the feral horse population is not managed, the horses’ grazing impact will continue to trigger unusually high rates of dune erosion in the future.
- To preserve the natural processes historically found on barrier islands, the study recommends setting up much larger fenced areas that can prevent feral horses from grazing.
Cite This Article
APA
De Stoppelaire GH, Gillespie TW, Brock JC, Tobin GA.
(2005).
Use of remote sensing techniques to determine the effects of grazing on vegetation cover and dune elevation at Assateague Island National Seashore: impact of horses.
Environ Manage, 34(5), 642-649.
https://doi.org/10.1007/s00267-004-0009-x Publication
Researcher Affiliations
- US Geological Survey, Center for Coastal and Watershed Studies, St. Petersburg, Florida 33701, USA. georgia.destoppelaire@my.FWC.com
MeSH Terms
- Animals
- Animals, Wild
- Conservation of Natural Resources
- Ecosystem
- Environmental Monitoring
- Feeding Behavior
- Horses
- Maryland
- Plant Development
- Population Dynamics
- Silicon Dioxide
- Soil
References
This article includes 4 references
- Klemas VV. Remote sensing of landscape-level coastal environmental indicators.. Environ Manage 2001 Jan;27(1):47-57.
- Taddese G, Saleem MA, Astatke A, Ayaleneh W. Effect of grazing on plant attributes and hydrological properties in the sloping lands of the East African highlands.. Environ Manage 2002 Sep;30(3):406-17.
- Seliskar DM. The response of Ammophila breviligulata and Spartina patens (Poaceae) to grazing by feral horses on a dynamic mid-Atlantic barrier island.. Am J Bot 2003 Jul;90(7):1038-44.
- McNaughton SJ. Grasses and Grazers, Science and Management.. Ecol Appl 1993 Feb;3(1):17-20.
Citations
This article has been cited 2 times.- Kilheffer CR, Underwood HB, Ries L, Raphael J, Leopold DJ. Effects of white-tailed deer (Odocoileus virginianus) exclusion on plant recovery in overwash fans after a severe coastal storm. AoB Plants 2019 Oct;11(5):plz059.
- Kim MK, Daigle JJ. Monitoring of vegetation impact due to trampling on Cadillac Mountain summit using high spatial resolution remote sensing data sets. Environ Manage 2012 Nov;50(5):956-68.
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