Rapid forest XXXX assessments of oceanic islands: a case study of the Hawaiian archipelago.

@entity505 @entity4612 @entity2101 @entity3
BACKGROUND: Spatially explicit forest @entity505 (C) monitoring aids conservation and climate change mitigation efforts, yet few approaches have been developed specifically for the highly heterogeneous landscapes of oceanic island chains that continue to undergo rapid and extensive forest C change. We developed an approach for rapid mapping of @entity2101 ( @entity2101 ; units  =  @entity4612 or metric tons  C  ha(-1)) on islands at a spatial resolution of 30  m (0.09  ha) using a combination of cost-effective airborne LiDAR data and full-coverage satellite data. We used the approach to map forest @entity2101 across the main Hawaiian Islands, comparing C stocks within and among islands, in protected and unprotected areas, and among forests dominated by native and invasive species. RESULTS: Total forest aboveground C stock of the Hawaiian Islands was 36 Tg, and @entity2101 distributions were extremely heterogeneous both within and across islands. Remotely sensed @entity2101 was validated against U.S. Forest Service FIA plot inventory data (R(2)  =  0.67; RMSE  =  30.4  Mg  C  ha(-1)). Geospatial analyses indicated the critical importance of forest type and canopy cover as predictors of mapped @entity2101 patterns. Protection status was a strong determinant of forest C stock and density, but we found complex environmentally mediated responses of forest @entity2101 to @entity3 . CONCLUSIONS: A combination of one-time airborne LiDAR data acquisition and satellite monitoring provides effective forest C mapping in the highly heterogeneous landscapes of the Hawaiian Islands. Our statistical approach yielded key insights into the drivers of @entity2101 variation, and also makes possible future assessments of C storage change, derived on a repeat basis from free satellite data, without the need for additional LiDAR data. Changes in C stocks and densities of oceanic islands can thus be continually assessed in the face of rapid environmental changes such as biological invasions, drought, fire and land use. Such forest monitoring information can be used to promote sustainable forest use and conservation on islands in the future.
