February 10, 2011

Australian Fisheries to Flourish?

Filed under: Adaptation, Animals, Extinctions

Conduct a search of the internet on “Global Warming and Fisheries” and treat yourself to nearly 1.5 million sites almost all proclaiming that the world’s fisheries are on the brink of disaster of biblical proportions due to global warming. Warmer sea temperatures completely alter the food chain, changes in sea currents add to the disaster, oceanic acidification compounds the mess, changes in climate alter the flow of nutrients to the sea, starving humans overharvest fisheries, and on and on it goes for another million sites. You must look long and hard for any evidence that climate change could benefit fisheries, or at least not devastate them.

An extraordinary article has appeared in Global Change Biology dealing with climate change, primary production of marine food webs, and implications for fisheries and threatened marine animals. The work was produced by 17 scientists from throughout many agencies in Australia and Canada; the work was supported financially by the Australian Research Council, the University of Queensland, CSIRO, and the Pew Fellows Program in Marine Conservation.

Brown et al. begin noting “Climate change is the most widespread anthropogenic threat that ocean ecosystems face. Globally, oceans are warming, becoming more acidic and have altered nutrient conditions. These environmental changes will directly affect the physiology of ocean organisms and hence their population dynamics. Changes in biomass of a species alter ecological interactions and have indirect effects throughout entire marine food webs. Climate change will thus affect all ocean organisms, change the composition of marine communities, and alter ecosystem function.” No surprise at all—we agree with their assessment.

The Brown et al. team “used 12 existing food web models of different Australian marine ecosystems, from tropical to temperate regions, to investigate effects of changing primary production on fishery catch, fishery value, biomass of species with conservation importance and indices of community composition that may indicate system-wide change.” We all realize that models are never perfect and each model has its shortcomings; nonetheless, they represent a set of tools for peering into the future to see how climate change will surely devastate the fisheries of Australia.

With the 12 models fired up and ready to go, the team had to make a decision regarding greenhouse gas emissions in the future. In their own words they note “We used predictions under the standard IPCC emission scenario A2. This scenario was devised as a high emission scenario, although recent observations suggest climate change is occurring more rapidly than this scenario predicts. IPCC emissions scenarios have not yet been updated, so we consider the A2 scenario as a mid-range scenario.” Interesting.

Now for the devastating results—the authors find “Under a plausible climate change scenario, primary production will increase around Australia and generally this benefits fisheries catch and value and leads to increased biomass of threatened marine animals such as turtles and sharks.” Stop the presses!!! Are they kidding us—did they not get the memo or read the million websites on the subject? Look at all the red in the maps (Figure 1) below—the red areas have an increase in fishery production, and the red areas are everywhere.


Figure 1. Change in fisheries landings (a, %) and value of landings (b, %) over 50 years for the Australian Ecosim model regions under the A2 greenhouse gas emission scenario. Regions shown on the maps are representative of the model regions only. Results are relative to simulations with no climate change (from Brown et al., 2010).

There must be a “catch” here—maybe the fisheries in general will be better off, but surely the endangered species will suffer? Don’t look now, but the maps in Figure 2 show the fate of sharks, turtles, seabirds, and marine mammals, and almost everywhere we look, the coastal areas are red (and red means more, not less in the future). Brown et al. state “Increases in primary productivity of the magnitude predicted by the primary production models can have large effects on the biomass of marine organisms and fishery catches. For most of the 12 ecosystems examined, predicted increases in primary production in Australia’s seas led to greater fisheries catch and supported higher biomasses of animals such as sharks, turtles and seabirds, which are currently threatened by human activities.” (See this World Climate Report article for more good news for sea turtles around Australia.)


Figure 2. Change in biomass abundance of conservation interest functional groups (%) over 50 years for the Australian Ecosim model regions under the A2 greenhouse gas emission scenario. Shown are change relative to no climate effects simulations for biomass of sharks (a), turtles (b), seabirds (c) and marine mammals (d). Regions shown on the maps are representative of the model regions only. Note that not all functional groups occur in all models.

There are some incredible statements including “We conclude that climate-driven primary production change needs to be considered by marine ecosystem managers and more specifically, that production increases can simultaneously benefit fisheries and conservation.” How about “primary production increases will provide opportunities to recover overfished fisheries, increase profitability of fisheries and conserve threatened biodiversity.”

Let’s look at the facts here. The large team of scientists runs all sorts of models, they consider the effects of changes in future climate, and they produce maps showing increases in productivity almost everywhere they looked and for everything alive in and out of the sea. Furthermore, they publish the results in one of the leading journals dealing with climate change and ecosystems. Did they receive any press coverage at all? Of course not, but had their work predicted problems ahead for Australia’s marine environment, they would have been featured in media outlets the world over and undoubtedly been featured in at least a million websites. But given the positive message of their work, they get featured in World Climate Report instead!

Reference:

Brown, C.J., E.A. Fulton, A.J. Hobday, R.J. Matear, H.P. Possingham, C. Bulman, V. Christensen, R.E. Forrest, P.C. Gehrke, N.A. Gribble, S.P. Griffiths, H. Lorenzo-Montes, J.M. Martin, S. Metcalf, T.A. Okey, R. Watson, and A.J. Richardson. 2010. Effects of climate-driven primary production change on marine food webs: implications for fisheries and conservation. Global Change Biology, 16, 1194–1212.




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