[Based in part on my evaluation for the Faculty of 1000, accessible only by subscription I'm afraid]
The pervasive detrimental impacts of overfishing on marine life and ecosystems have been widely publicized in recent years, ratcheting up calls for stricter regulation and protection. A counter-argument commonly heard in debates on this issue is that fishing (like coal mining, oil drilling, pillaging of old-growth forests, etc.) provides essential jobs, revenue, and food, particularly in poor countries. It’s jobs and food for people versus the environment, you heartless misanthropic tree-huggers.
Or is it?
Answering this question is tricky. For fishing, it requires good estimates of a fish population’s (or community’s) “maximum sustainable yield” (MSY) — the precise quantity of fish that can be harvested each year while keeping the population healthy and producing at maximal rate for the long haul. Estimating this quantity (and “estimating” is a kind way of saying it, but don’t get me started) requires a lot of data and hard work, which essentially means that it doesn’t happen in most of the world’s fisheries.
In a new paper, Uta Srinivasan and colleagues cleverly sidestepped this problem by first calibrating an empirical relationship between maximum sustainable yield and the maximum recorded catch for those fisheries where such data were available. This is a key step forward because there are lots more data available on recorded catch (since it’s an index of the success and profits of fishers they have some incentive to record it) than there are for MSY. It turns out that the two variables are quite highly correlated (R2=0.84) — as might be expected since there is little incentive to reduce fishing when the population is producing well. In other words, fishers tend instinctively to find the sweet spot (mathematically speaking) and stay there.
So the authors were able to use this general relationship to estimate MSY for fisheries throughout the rest of the world, where MSY data are limited or nonexistent. Then they estimated the difference between MSY and actual yield of overfished stocks, what is in fact brought back to the dock. This difference — between what is and what could be — they term the “overfishing debt”, measured in currencies of biomass, food energy, or revenues. Their analysis found that 16-31% of world fish stocks are overfished, in line with other recent estimates.
But the new — and troubling — finding was that, globally averaged, gross revenue lost to fishing beyond sustainable levels was 6-35% of the landed value of the fisheries, depending on assumptions. Interestingly (indeed perversely), these losses are similar in magnitude to the government subsidies that support excess fishing capacity (again, ironically, largely to support jobs). Most troubling of all, the analysis showed that overfishing debt fell most heavily on poor developing nations: among the 43, mostly African, ‘Low-Income Food-Deficit Countries’ analyzed, losses of potential catch to overfishing averaged a staggering 75% of actual landings. Thus, an estimated 20 million people worldwide were undernourished as a result of unsustainable fishing. And that’s on top of the environmental destruction we already knew about.
In short, this paper shows that global overfishing results not only in the well-known degradation of biodiversity and ecosystems but also in ‘overfishing debt’, a paradoxical — and substantial — loss of revenue and food security, particularly in the nations that can least afford it.
For some possible solutions, see the final paragraphs of this summary.