Shrubland Detection

Executive Summary

Novel plant communities reshape landscapes and pose challenges for land cover classification and mapping that can constrain research and stewardship efforts. In the US Northeast, emergence of low-statured woody vegetation, or ‘shrublands’, instead of secondary forests in post-agricultural landscapes is well-documented by field studies, but poorly understood from a landscape perspective, which limits the ability to systematically study and manage these lands. To address gaps in classification/mapping of low-statured cover types where they have been historically rare, we developed models to predict ‘shrubland’ distributions at 30m resolution across New York State (NYS), using machine learning and model ensembling techniques to integrate remote sensing of structural (airborne LIDAR) and optical (satellite imagery) properties of vegetation cover. We first classified a 1m canopy height model (CHM), derived from a “patchwork” of available LIDAR coverages, to define shrubland presence/absence. Next, these non-contiguous maps were used to train a model ensemble based on temporally-segmented imagery to predict ‘shrubland’ probability for the entire study landscape (NYS). Approximately 2.5% of the CHM coverage area was classified as shrubland. Models using Landsat predictors trained on the classified CHM were effective at identifying shrubland (test set AUC=0.893, real-world AUC=0.904), in discriminating between shrub/young forest and other cover classes, and produced qualitatively sensible maps, even when extending beyond the original training data. After ground-truthing, we expect these shrubland maps and models will have many research and stewardship applications including wildlife conservation, invasive species mitigation and natural climate solutions. Overall our results compared favorably in terms of accuracy with existing LULC products, suggesting that incorporation of airborne LiDAR, even from a discontinuous patchwork of coverages, can improve LULC classification of historically rare but increasingly prevalent ‘shrubland’ habitats across broader areas.

People

Key Papers

  • Jake M Alexander, Jeffrey M Diaz, and Jonathan M Levine. Novel competitors shape species’ responses to climate change. Nature, 525:515–518, 2015. doi: 10.1038/nature14952.
  • James R Anderson, Ernest E Hardy, John T Roach, and Richard E Witmer. A land use and land cover classification system for use with remote sensor data, volume 964. US Government Printing Office, 1976.
  • Jesslyn F. Brown, Heather J. Tollerud, Christopher P. Barber, Qiang Zhou, John L. Dwyer, James E. Vogelmann, Thomas R. Loveland, Curtis E. Woodcock, Stephen V. Stehman, Zhe Zhu, Bruce W. Pengra, Kelcy Smith, Josephine A. Horton, George Xian, Roger F. Auch, Terry L. Sohl, Kristi L. Sayler, Alisa L. Gallant, Daniel Zelenak, Ryan R. Reker, and Jennifer Rover. Lessons learned implementing an operational continuous united states national land change monitoring capability: The land change monitoring, assessment, and projection (lcmap) approach. Remote Sensing of Environment, 238: 111356, 2020. ISSN 0034-4257. doi: 10.1016/j.rse.2019.111356.

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Other References