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Mapping of Phragmites in estuarine wetlands using high-resolution aerial imagery

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Phragmites australis is a widespread invasive plant species in the USA that greatly impacts estuarine wetlands by creating dense patches and outcompeting other plants. The invasion of Phragmites into wetland ecosystems is known to decrease biodiversity, destroy the habitat of threatened and endangered bird species, and alter biogeochemistry. While the impact of Phragmites is known, the spatial extent of this species is challenging to document due to its fragmented occurrence. Using high-resolution imagery from the National Agriculture Imagery Program (NAIP) from 2017, we evaluated a geospatial method of mapping the spatial extent of Phragmites across the state of DE. Normalized difference vegetation index (NDVI) and principal component analysis (PCA) bands are generated from the NAIP data and used as inputs in a random forest classifier to achieve a high overall accuracy for the Phragmites classification of around 95%. The classified gridded dataset has a spatial resolution of 1 m and documents the spatial distribution of Phragmites throughout the state’s estuarine wetlands (around 11%). Such detailed classification could aid in monitoring the spread of this invasive species over space and time and would inform the decision-making process for landscape managers.

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Data availability

The classified Phragmites dataset from model 3 generated for this article is available through Zenodo at The GEE code used for the classification of Phragmites from NAIP imagery is available at


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We thank the reviewers for their constructive criticism of an earlier version of this manuscript. We thank Bruce Vasilas for his guidance in the field.


This publication was made possible by the National Science Foundation EPSCoR grant no. 1757353 and the State of Delaware. This work was also supported by the NASA EPSCoR grant (DE-80NSSC20M0220). The lead author was supported by the NASA Delaware Space Grant College and Fellowship Program (80NSSC20M0045).

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Conceptualization: Matthew Walter. Methodology: Matthew Walter and Pinki Mondal. Writing—original draft preparation: Matthew Walter. Writing—review and editing: Pinki Mondal. Funding acquisition: Matthew Walter and Pinki Mondal.

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Correspondence to Matthew Walter.

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Walter, M., Mondal, P. Mapping of Phragmites in estuarine wetlands using high-resolution aerial imagery. Environ Monit Assess 195, 478 (2023).

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