Harmonization of Forest Disturbance Datasets of the Conterminous United States from 1986-2011

A wide range of spatial forest disturbance datasets exist for the conterminous United States, yet inconsistencies between map products arise because of differing programmatic objectives and methodologies. Researchers harmonized maps from multiple data sources (i.e., Global Forest Change, Landfire Vegetation Disturbance, National Land Cover Database, Vegetation Change Tracker, Web-enabled Landsat Data, and Monitoring Trends in Burn Severity) using a pixel-based data fusion process. The harmonization process, which involves fitting common class ontologies and testing spatial congruency, reconciled differences in forest harvest/other and forest fire across four intervals (1986-1992, 1992-2001, 2001-2006, and 2006-2011) by relying on convergence of evidence across all datasets available for each interval. Pixels with high agreement across datasets were retained and pixels mapped by only one dataset were deleted. Results indicate that harmonization of readily-available data increases data utility by incorporating causality information across input datasets, extending the monitoring period, and improving user�s accuracies. However, conservative rules for flagging disturbance contribute to lower producer�s accuracies relative to the best available stand-alone maps. Omission errors remain high for all forest disturbance maps due to underlying limitations in Landsat classification algorithms.