Declining ocean health: It’s the economy, stupid

samurai_tuna_worker.jpgI know, I used the same subtitle for another recent post.  But I’m not recycling titles out of laziness — well, not entirely anyway. I do so here to highlight the simple, yet perversely (and perhaps intentionally) misunderstood theme whose centrality to the broad range of environmental problems is increasingly obvious.  Hence the “stupid” bit.

The simple, central, misunderstood theme is this: Despite the rosy optimism one hears from various quarters, We can’t grow our way out of our environmental problems. Yes, of course technology can help, and we need creative entrepeneurship.  But blind reliance on the “free” market is not going to do the trick.

The latest evidence on this front comes from an analysis, across 102 countries, of the impacts of human population density, urbanization, and economic growth on the condition of marine biological communities.  Rebecca Clausen and Richard York set out to quantify the role of changing human social development and economic institutions in the accelerating decline of marine biological diversity.  It’s well-recognized that human impact on the environment is ultimately a result of demographic and economic factors. But there is disagreement about how these processes affect the environment.  Indeed, as they note:

“Neoclassical economists argue that environmental quality is a luxury good and, therefore, only affluent societies are willing to heavily invest in environmental protection. The environmental Kuznets curve (EKC) describes this hypothetical relationship between affluence and environmental quality. The EKC hypothesis suggests that environmental problems escalate in the early stages of economic development, but eventually a tipping point is reached, after which further economic growth leads to improvements in environmental quality.”

In other words, the argument goes, once you get to be as rich as the United States, it’s all good.  The idea is that affluence leads to better resource and environmental management.  For example, we often hear that concern over global overfishing is alarmist because we have (some) good fishery management practices in effect in civilized places like the USA, Canada, and New Zealand. Though the latter bit is true, it’s not clear that such practices are becoming more widespread in time or space.

fishing_down_the_food_web.jpgIn fact, there is considerable evidence against the hypothesis that economic development improves environmental quality on anything more than a local scale.  But the aim of this paper was to test the EKC hypothesis broadly, by considering diverse marine ecosystems rather than single fished species or stocks.  As an indicator of marine biodiversity they used the “mean trophic level” of fisheries catches between 1960 and 2003.  The basic rationale here is twofold.  First, mean trophic level roughly estimates the proportion of the catch that is made up of big top predators (tunas, cod, etc.), compared with, say, anchovies, and the abundance of top predators is in turn a good indicator of the degree to which the ecosystem supports a taxonomically and functionally diverse biological community.  Second, fishing tends to target top predators, so the decline in mean trophic level signals increasing human impact.  Indeed, the targeting of top predators is consistent enough that Daniel Pauly and colleagues famously summarized the succession of industrial fishing impacts as “fishing down the food web” (see the figure).

Clausen and York developed mathematical models to capture the effects on mean trophic level of human population, per capita GDP, degree of urbanization (% of population living in urban areas).  The model included various terms to account for changes in marine productivity, geographic expansion of fisheries, changes in fishing effort, and so on.

What they found is important, if not terribly surprising.  First of all, at the risk of stating the obvious, countries with higher populations, urbanization, and economic growth caught more fish.  Overall, the healthy structure of marine ecosystems, as indexed by mean trophic level of catch, declined as economic growth, urbanization, and human population size increased.

clausen_york_figure2.gifBut there were some interesting twists with respect to the EKC hypothesis.  For example, fishery catch roughly matched the EKC predictions, dramatically increasing with per capita GDP during early stages of economic development, reaching a plateau at ~ US $3000, then declining modestly.  Urbanization, however, showed a pattern opposite to that predicted by EKC:  fish catch by a country initially declined with urbanization, then increased again after ~36% of the population was living in cities.   Importantly, “the total effect of GDP per capita [on MTL] was monotonically negative”, meaning roughly that as average individual income increased, the abundance of predators in that country’s exclusive economic zone declined (see graph at left).  This effect was strongest during early stages of economic development. On the bright side, growth in per capita GDP above $10,000 had little effect on mean trophic level of catches.

Long story short – “Our results contradicted both the economic and urbanization EKC hypotheses, indicating that economic development and urbanization led to marine biodiversity loss. Likewise, population growth clearly led to depletion of marine fisheries.” From a policy perspective, the take-home message is the “grow-your-way-out-of-your-problems” economic theory championed by the likes of Julian Simon and Bjorn Lomberg doesn’t work, at least fr marine fisheries and ecosystem health.

fullnet.gifOne might be forgiven for thinking this would be common sense.  How can building more buildings and roads and ships and airplanes and iPods and vacuuming up the earth’s living and nonliving resources to fuel it all reduce our impact on the environment? The simple fact is: it can’t.  Alas, that sense is not in fact common, at least not in mainstream economic theory, which of course is the philosophical guiding light of modern civilization.  Fortunately, there is growing recognition that the physical basis on which the economy is built is finite, and that a sustainable future will require a steady-state economy.

Now, I don’t want to be misunderstood, since I know certain readers may jump to conclusions here. Obviously, economic development is important, and people need food, of which marine fish are a very important source worldwide and will continue to be.  It would be silly to think that we can or even should stop fishing.  But this and a growing body of other evidence are making it clear that humanity will have to manage marine fisheries and other interactions with the environment much more thoughtfully than we have done if we expect our grandkids to be enjoying them too.  Pretending that “free”-market economics alone will magically solve such problems is a fantasy.

[Original source: Clausen, R. and R. York. 2007. Economic Growth and Marine Biodiversity: Influence of Human Social Structure on Decline of Marine Trophic Levels. Conservation Biology doi:10.1111/j.1523-1739.2007.00851.x]

About Emmett Duffy

I am a Natural Patriot and an ecologist with expertise in biodiversity and its importance to human society. My day job is Professor of Marine Science at the College of William and Mary in Virginia.
This entry was posted in Biodiversity, Oceans, Politics, Sustainability and tagged , , , , , . Bookmark the permalink.

10 Responses to Declining ocean health: It’s the economy, stupid

  1. Mr. R says:

    I think the issue is much more complicated than GDP/urbanization causing a decline in average trophic level of fish catch. I didn’t read the article, but do the authors take into account the fact that lots of little fish–like sardines and anchovies–are caught to be processed into food for farmed fish like salmon and striped (or is it black?) bass? The consumption of these farmed fish has sky-rocketed and would certainly shift demand away from wild salmon in favor of wild baitfish.

    And culinarily, the scene has changed–Ahi tuna is still popular, but people have been shying away from heavy-metal loaded swordfish and the like for years.

    I agree that the economy plays a role, but culture (e.g., what fish are fashionable, how important are particular fish to the national diet), prevalence of fish farming, etc… are going to mediate the impacts of GDP on what happens in our oceans.

  2. Mr. R says:

    Oh, and one other question.

    “the abundance of top predators is in turn a good indicator of the degree to which the ecosystem supports a taxonomically and functionally diverse biological community.”

    Is it really?

    At least terrestrially, you can have pretty damn un-diverse communities support an abundant, diverse predator assemblage–dozens of predators are supported on lemmings alone. Is “the abundance of top predators” really the best proxy for a “functionally diverse biological community”? I mean it’s relatively easy to measure and the researchers knew the answer to their question before they asked it (everyone knows there are fewer big fish and economies worldwide are growing), but does that mean it’s the best thing to use?

  3. Emmett Duffy says:

    Good questions, Mr. R. The pattern of “fishing down the food web” has indeed been challenged based on the fact that MTL of catch could decline because of adding catch low in the food web, as well as loss of predators up top. See for example, the paper by Essington et al, which documents exactly this phenomenon for several marine areas.

    Clausen and York tested for this possibility by also running their analyses with species at the lowest levels of the food chain excluded. They got basically the same results, so in this case at least, addition of low-level fisheries appears not to explain the broad-scale trend in declining MTL.

    I don’t think the authors specifically accounted for changing tastes, mercury scares, etc. I don’t know of any data on this but I would be pretty surprised if such changes would have a big effect on patterns at this scale of international analysis. Certainly every restaurant I’ve been to in recent years continues to serve big predators at the top of their menus, whichmust means someone is buying them.  Me, for example (yes, I’m guilty). 

    MTL is certainly not the ideal measure for “marine biodiversity” as a whole. On the other hand, I suspect it is a pretty good proxy for changing community structure, and probably also correlates with changing species diversity, given the well documented focus of most fisheries on species at higher trophic levels. If MTL is declining (especially in analyses where lowest levels species have been excluded), that is probably a pretty reliable sign that the overall abundance and relative species composition of the community has been changed significantly.

    You are undoubtedly correct that culture, fish farming, etc, will also influence these trends. I am a bit less optimistic about fish farming as a savior of the oceans, given that most farmed fish (e.g., salmon) are carnivores that are often fed with . . . wild caught fish! But tilapia and catfish and some other relatively low-footprint operations should be part of the solution.

  4. Dave Gardner says:

    I think it’s pretty obvious, to those willing to really see, that the environmental Kuznets curve is actually incomplete. There is, apparently, another uptick in the inverted U, more like a complete sine wave. It’s clear the developed world is now in the midst of that uptick, undoing much of the environmental good we accomplished before overpopulation multiplied by obsession with economic growth spiraled out of control. So it’s great to see scientists beginning to question this little bit of ammo from the growth-boosters’ arsenal. Thanks!

    Dave Gardner
    Hooked on Growth: Our Misguided Quest for Prosperity

  5. John Feeney says:


    Excellent post, as usual!

    There seems to be a large body of research saying the EKC just isn’t very meaningful. I included a few links in an old post on my blog:

    I like what a writer for the Simpsons had to say about our obsession with economic growth:

    That said, if we did turn the earth into an apocalyptic hellscape, a sick part of me would find it thrilling.

    I would enjoy watching dazed stockbrokers and ad men clawing at the dirt for edible roots. I’d remind them that they’d been warned of their folly…


  6. Emmett Duffy says:

    Thanks, guys, for the support and the links. John’s link to his post at Growth is Madness, along with the long list of comments in response to it, is well worth reading.

    As pointed out there, a key issue in judging (and killing) the EKC idea is one of scale — we are now dealing with the entire planet, which is a closed system, not the national or regional economies on which classical economics was based, which assume implicitly that there is a big wide world of resources out there external to the economic system. There ain’t anymore.

  7. Hey Emmett,
    Nice post – and well written. As an editor for The Issue, a recently launched Blog Newspaper, I’ve decided to feature this post in the Science and Health Section today.

    You can find a brief excerpt and a link at


  8. Emmett Duffy says:

    Thanks Jean-Baptiste — The Isssue looks great! I will have to bookmark it.

  9. Blake Nagel says:

    Hi Emmett,

    I am impressed by the detailed description you give here on this article. Our oceans are indeed in dire straits and I’m angered to see that certain activities are still legally supported by certain countries.

    Things such as shark hunting and whale killings should be forbidden once and for all by ALL nations worldwide as these animals play such a huge part in keeping the ecology in pristine order.

  10. Nucbuddy says:

    It would be silly to think that we can […] stop fishing.

    What makes you think that we can’t stop fishing the oceans?

    Re oceanic fishing ([Ehrlich-Schneider]): Let’s bet on fish consumption per person, which includes not just the ocean catch but also fish farming.