What can today’s models tell us about the future of the Baltic Sea fish?

Susa Niiranen

Postdoctoral researcherStockholm Resilience Centre

susa.niiranen@stockholmresilience.su.se

photos by A. & I. Lastumäki

Helsinki, September 16, 2015

Multiple pressures define Baltic Sea future

(Fig. source: Baltic Stern, 2013)

ECHAM5-r1-A1BECHAM-r3-A1B

ECHAM-A2

Climate (GCMs)

Nutrient loads

BALT

SEM

, ERG

OM

, RCO

-SCO

BIas today (REF)

increase (BAU)(continued intensification

of agriculture)

decrease (BSAP)(Baltic Sea Action plan) Ba

ltPro

Web

, Ew

E fo

od w

eb m

odel

FWMBGMs

salinity

temperature

salinity

prim. prod.

hypoxic A

cod RV

cod fishing

F 1.1

F 0.3

Multimodel scenario approach(ECOSUPPORT, Meier et al. 2012)

Future biomass projections (2010-2100) in combined climate, nutrient load and cod fishing scenarios.

(Niiranen et al. 2013)

reference nutrient loads

reduced nutrient loads(BSAP)

Future food web projections (-2100)

high nutrient loads

So what does the model tell us?

• Climate change is likely to set boundaries for how the future Baltic Sea ecosystem will look like (e.g., effects on cod).

• Regional management scenarios can have high impact for Baltic Sea future:

Cod dominated, with eutrophication levels and clupeid biomass as today (best-case scenario), or

Sprat dominated, with very low biomasses of cod and twice as high eutrophication

We may not get the “old” Baltic Sea back, but with right actions it is possible to have a well-functioning sea that can provide us with ecosystem services.

Modelling the social-ecological system

(Lade et al. PNAS 2015)

• Lade, Niiranen, Hentati-Sundberg et al. 2015. An empirical model of the Baltic Sea reveals the importance of social dynamics for ecological regime shifts. PNAS, 112(35):11120-11125.

• Niiranen, Yletyinen, Blenckner et al. 2013. Combined effects of global climate change and regional ecosystem drivers on an exploited marine food web. Global Change Biology, 19:3327-3342.

• Meier, Andersson, Arheimer et al. 2012. Comparing reconstructed past variations and future projections of the Baltic Sea ecosystem—first results from multi-model ensemble simulations . Environmental Research Letters 7.

Thank you.

References

Acknowledgements to GreenMar and ECOSUPPORT; and Koneen Säätiö and The W. & A. de Nottbeck Foundation for WS and travel support.