Marine Rewilding?

It's amazing what you'll catch in the letters to the editor sometimes.  In the latest issue of Fisheries Magazine is a classic back-and-forth editorial origination from an article by researcher John. C. Briggs.  At first my interest was piqued simply by the fact that there was something ocean-related (since the start of my subscription Fisheries has been utterly dominated by freshwater articles), but reading the debate motivated me to go back and track down the original article.  What I found was one of the more unusual takes I've seen on the management of Atlantic fisheries, and an interesting parallel with a highly controversial conservation strategy.



The idea behind Briggs (2008) is basically this: you can replace depleted species in the North Atlantic by replacing them with similar species from the North Pacific.  Since areas with low biodiversity are both more vulnerable to overfishing and less likely to recover, Briggs' idea is to increase biodiversity by intentionally introducing Pacific species to the Atlantic.  Not just any species, but large, commercially-important fish like the Pacific versions of cod and halibut.  In theory this provides the dual benefits of giving fishermen something to catch other than the beleaguered Atlantic species and filling the niches vacated by the overfishing of Atlantic cod, halibut, haddock, etc.  Many Atlantic and Pacific species share a common ancestry, and Briggs suggests that this may be enough to help the Pacific species fit in.

As I read this paper, it occurred to me that I've seen an eerily similar argument before.  The Pleistocene Rewilding movement is nicely summarized in Donlan et al. (2006), a paper epic in its scope (and authored by so many researchers that typing it into the References section takes almost as long as reading the paper).  Rewilding is essentially the restoration of the North American ecosystem to the pre-human stage.  North America was once the stomping ground of mammoths, giant sloths, saber-toothed tigers and other badass megafauna, and when Homo sapiens migrated over from Asia it rampaged around like a bull in a china shop, driving everything larger than the polar bear to extinction.  The result is a series of gaps in the ecosystem large enough to, well, fit a woolly mammoth, from plants that were meant to be dispersed by enormous animals to grazers like the pronghorn elk that have obviously evolved to escape predators that just aren't around anymore.  Donlan and company argue that the only way to truly restore the North American ecosystem is to bring in proxy animals to refill those empty niches, and a lot of extinct American megafauna was pretty closely related to currently extant African megafauna.   Think elephants to replace mammoths and leopards to chase the pronghorn elk, and you've got the idea.  And it immediately becomes obvious why this is such a controversial stance.

So what Briggs is suggesting is no less than a form of marine rewilding.  He's not trying to bring back prehistoric species, but he is in favor of transplanting species from one geographic area to another in order to offset human impacts.  The issue is that the North Atlantic has been fished since prehistory, so it's nearly impossible to tell what the "pre-human" state was.  Another interesting aspect is the relatively open nature of the ocean.  While the Atlantic and Pacific have more distinct species than not, a lot of the larger, more migratory species readily inhabit both oceans.  The North Atlantic and Pacific both share several species of sharks (including the spiny dogfish), tuna, cetaceans, and other wide-ranging marine megafauna.  Many of these wide-ranging species function as predators of both the Atlantic and Pacific species Briggs intends to transplant.  Would the presence of Pacific cod benefit the Atlantic species by taking the predatory heat off as well?  And would this be enough to mitigate the inevitable conflict should Atlantic cod recover enough to start taking back their old territory?

It makes for an interesting discussion, but the long-term risks and benefits of what Briggs somewhat euphemistically calls "proactive management" are poorly understood.  What we do have is a long history of intentional freshwater introductions, the results of which have been spotty at best.  We also have just as long a history of harmful marine invasive species.  The real question is who, exactly, marine rewilding is really trying to benefit.  It may refill important niches, and it may also lead to the wholesale displacement of Atlantic species (which are starting out at a disadvantage being overfished).  What it does do, however, is give fishermen something to catch, which is ultimately one of the most important long-term goals of fisheries management.  Is preserving the commercial fishing industry worth this massive-scale experiment in marine ecology?  I'll leave that up to the Comments section.

Briggs, J. (2008). The North Atlantic Ocean: Need for Proactive Management Fisheries, 33 (4), 180-185 DOI: 10.1577/1548-8446-33.4.180

Josh Donlan C, Berger J, Bock CE, Bock JH, Burney DA, Estes JA, Foreman D, Martin PS, Roemer GW, Smith FA, Soulé ME, & Greene HW (2006). Pleistocene rewilding: an optimistic agenda for twenty-first century conservation. The American naturalist, 168 (5), 660-81 PMID: 17080364