Salmon abundance and patterns of forest greenness as measured by satellite imagery

Linkages across ecosystems can shape productivity. Salmon carcasses are exemplary of cross-system linkages, because they can fertilize riparian vegetation and shape patterns of terrestrial biodiversity. Detection of salmon fertilization effects has been confined to field-based studies that are limited in scale. Here we use satellite images to quantify the effects of salmon on greenness of riparian vegetation. We measure tree greenness across spatial and temporal gradients of salmon fertilization effects in two regions. In the first case study, we find that deciduous trees are greener in years following large salmon spawning events, and that the magnitude of this effect was related to the specific abundance of spawning salmon. In the second case study we compare greenness of mixed evergreen and deciduous forests across different watersheds that have different salmon spawning densities. We found greenness was related positively to salmon spawning density near streams with high evergreen cover and flat stream banks. These findings suggest that the effect of salmon carcasses on riparian vegetation may be detectable from space. Further work on this approach, especially with high spatial, temporal and spectral data, may allow estimation of the spatial extent of nutrient enrichment from salmon carcasses and aid ecosystem-based management to protect important ecosystem linkages.