Open AccessSoutheast Alaskan kelp forests: inferences of process from large-scale patterns of variation in space and time
Author(s) -
Torrey R. Gorra,
Sabrina C. R. Garcia,
Michael R. Langhans,
Umihiko Hoshijima,
James A. Estes,
Pete Raimondi,
M. Tim Tinker,
Michael C. Kenner,
Kristy J. Kroeker
Publication year - 2022
Publication title -
proceedings - royal society. biological sciences/proceedings - royal society. biological sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.342
H-Index - 253
eISSN - 1471-2954
pISSN - 0962-8452
DOI - 10.1098/rspb.2021.1697
Subject(s) - otter , kelp , kelp forest , trophic cascade , ecology , trophic level , sea urchin , biomass (ecology) , occupancy , abundance (ecology) , geography , fishery , biology , environmental science , food web
Humans were considered external drivers in much foundational ecological research. A recognition that humans are embedded in the complex interaction networks we study can provide new insight into our ecological paradigms. Here, we use time-series data spanning three decades to explore the effects of human harvesting on otter–urchin–kelp trophic cascades in southeast Alaska. These effects were inferred from variation in sea urchin and kelp abundance following the post fur trade repatriation of otters and a subsequent localized reduction of otters by human harvest in one location. In an example of a classic trophic cascade, otter repatriation was followed by a 99% reduction in urchin biomass density and a greater than 99% increase in kelp density region wide. Recent spatially concentrated harvesting of otters was associated with a localized 70% decline in otter abundance in one location, with urchins increasing and kelps declining in accordance with the spatial pattern of otter occupancy within that region. While the otter–urchin–kelp trophic cascade has been associated with alternative community states at the regional scale, this research highlights how small-scale variability in otter occupancy, ostensibly due to spatial variability in harvesting or the risk landscape for otters, can result in within-region patchiness in these community states.