Ecosystems

, Volume 10, Issue 6, pp 877–889

Human-induced Trophic Cascades and Ecological Regime Shifts in the Baltic Sea

  • Henrik Österblom
  • Sture Hansson
  • Ulf Larsson
  • Olle Hjerne
  • Fredrik Wulff
  • Ragnar Elmgren
  • Carl Folke
Article

DOI: 10.1007/s10021-007-9069-0

Cite this article as:
Österblom, H., Hansson, S., Larsson, U. et al. Ecosystems (2007) 10: 877. doi:10.1007/s10021-007-9069-0

Abstract

The ecosystems of coastal and enclosed seas are under increasing anthropogenic pressure worldwide, with Chesapeake Bay, the Gulf of Mexico and the Black and Baltic Seas as well known examples. We use an ecosystem model (Ecopath with Ecosim, EwE) to show that reduced top-down control (seal predation) and increased bottom-up forcing (eutrophication) can largely explain the historical dynamics of the main fish stocks (cod, herring and sprat) in the Baltic Sea between 1900 and 1980. Based on these results and the historical fish stock development we identify two major ecological transitions. A shift from seal to cod domination was caused by a virtual elimination of marine mammals followed by a shift from an oligotrophic to a eutrophic state. A third shift from cod to clupeid domination in the late 1980s has previously been explained by overfishing of cod and climatic changes. We propose that the shift from an oligotrophic to a eutrophic state represents a true regime shift with a stabilizing mechanism for a hysteresis phenomenon. There are also mechanisms that could stabilize the shift from a cod to clupeid dominated ecosystem, but there are no indications that the ecosystem has been pushed that far yet. We argue that the shifts in the Baltic Sea are a consequence of human impacts, although variations in climate may have influenced their timing, magnitude and persistence.

Keywords

eutrophicationfishingmarine mammalpredationregime shifttrophic cascade

Supplementary material

10021_2007_9069_MOESM1_ESM.pdf (98 kb)
APPENDIX (PDF 1.4 Mb)

Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Henrik Österblom
    • 1
    • 2
  • Sture Hansson
    • 1
  • Ulf Larsson
    • 1
  • Olle Hjerne
    • 1
  • Fredrik Wulff
    • 1
    • 2
  • Ragnar Elmgren
    • 1
  • Carl Folke
    • 1
    • 2
    • 3
  1. 1.Department of Systems EcologyStockholm UniversityStockholmSweden
  2. 2.Stockholm Resilience CentreStockholm UniversityStockholmSweden
  3. 3.The Beijer International Institute of Ecological EconomicsThe Royal Swedish Academy of SciencesStockholmSweden