Just Out: Assessing risks to marine ecosystems with...
Bland, L.M., Watermeyer, K.E., Keith, D.A., Nicholson, E., Regan, T.J. and Shannon, L.J., 2018. Assessing risks to marine ecosystems with indicators, ecosystem models and experts. Biological Conservation, 227, pp.19-28.
Assessing risks to marine ecosystems is critical due to their biological and economic importance, and because
many have recently undergone regime shifts due to overfishing and environmental change. Yet defining col-
lapsed ecosystem states, selecting informative indicators and reconstructing long-term marine ecosystem
changes remains challenging. The IUCN Red List of Ecosystems constitutes the global standard for quantifying
risks to ecosystems and we conducted the first Red List assessment of an offshore marine ecosystem, focusing on
the southern Benguela in South Africa. We used an analogous but collapsed ecosystem – the northern Benguela –
to help define collapse in the southern Benguela and derived collapse thresholds with structured expert elici-
tation (i.e. repeatable estimation by expert judgment). To capture complex ecosystem dynamics and reconstruct
historical ecosystem states, we used environmental indicators as well as survey-, catch- and model-based in-
dicators. We listed the ecosystem in 1960 and 2015 as Endangered, with assessment outcomes robust to alter-
native model parametrizations. While many indicators improved between 1960 and 2015, seabird populations
have suffered large declines since 1900 and remain at risk, pointing towards ongoing management priorities.
Catch-based indicators often over-estimated risks compared to survey- and model-based indicators, warning
against listing ecosystems as threatened solely based on indicators of pressure. We show that risk assessments
provide a framework for interpreting data from indicators, ecosystem models and experts to inform the man-
agement of marine ecosystems. This work highlights the feasibility of conducting Red List of Ecosystems as-
sessments for marine ecosystems.