Thursday, May 22, 2014

Another Pleasure Becomes A Vice, Perhaps ~ A Cautionary Tale

I opened my summer cottage last week and then wandered down to the beach to see what the winter had wrought.

Nothing dramatic.  This day shells dotted the shoreline – as many as expected and the usual suspects as far as I could tell.

A few days before, I’d picked up the Washington Post’s Health and Science section (graces each Tuesday’s newspaper) and found an article with the dread-inducing title of Don’t Pick Up the Seashells Down by the Seashore (print version of May 13, 2014, see below for a link to the online article).  The author was science writer Jason G. Goldman.

Damn, another pleasure transformed into a vice.

To be fair to Goldman, I doubt he drafted this title.  Titles in newspapers are fluid things – the online version of the article is titled Collecting Seashells and Grooming Sand May Damage Beach Ecosystems, A Study Finds.

But it’s easy to see why someone chose that specific title for his piece in the print version of the newspaper because Goldman does strike a decidedly negative note, beginning his article with this admonition:
You might think twice next time you snag a seashell from the beach and drop it into your pocket.  You might be altering the seaside environment.
He buttresses this opening warning by referring to a scientific study “more than 30 years in the making” that, he asserts, makes that very claim – collecting seashells could be bad for beaches.

That study, the be-all and end-all of Goldman’s newspaper story, appeared January, 2014, in the open access, peer reviewed science journal PLOS ONE under the title Vanishing Clams on an Iberian Beach:  Local Consequences and Global Implications of Accelerating Loss of Shells to Tourism.  Michal Kowalewski and colleagues report on the results of a detailed analysis of the abundance of empty mollusk shells on Llarga Beach (Platja Llarga), a small beach (slightly more than a third of mile long) in Spain, on the Mediterranean, southwest of Barcelona.  The map below is focused on Llarga Beach.  Zooming out will help orient the beach on Spain’s Mediterranean coastline.

Between July, 1978, and July, 1981, monthly tallies of shell abundance were conducted; three decades later, the authors undertook a more limited series of counts (monthly from August to October, 2008, and monthly from July, 2009, to June, 2010).

Their findings?

As a proxy for all shells, they concentrate on the three dominant bivalves that appear on this shore.  The average number of such shells for each tally in the 1978-1981 period was 1,506.5; thirty year later, in the 2008-2010 period, the average count was 578.3.  This is a 61.6 percent decline, or, as Kowalewski et al. put it, the “shells at the shoreline of Llarga Beach were almost three times more abundant three decades ago, on average . . . .” (p. 4)

Does this matter?

The researchers describe various functions that shells play in the ecosystem of the shoreline, among them:  stabilizing beaches, providing shelter for different kinds of organisms including algae, hermit crabs, and fish, and offering surfaces for colonization by other organisms.  Further, when dissolved, shell material returns different elements, e.g., carbon and oxygen, to marine waters.

The authors dispose of a host of potential factors that might explain the drop in the number of shells.  It cannot be pegged to loss of a particular species because the relative distribution of shells from these mollusk species differed little from the first period to the other.  There was no significant alteration in beach topography, urbanization of adjacent properties, or the harvesting of shellfish and other fishery activities.  Further, no change in local weather conditions such as average monthly temperatures was noted; average wave heights were little changed (apparently this is enough evidence to show that no change in onshore currents had moved the shells); and there was no evidence of an increase in predation on the bivalves by gastropods.

Having struck down these various potential agents, Kowalewski et al. look at tourism.  They compiled data on the growth in the number of tourists visiting this shoreline and concluded there was a “significant negative correlation . . . between tourism and shell abundance . . . .”  Overall, shell abundance dropped by a factor of 2.62, and local tourism increased by a factor of 2.74.  The correlation was particularly strong during the summer months.  “The increase in strength of the correlation with increase in tourist arrivals [in the summer] is particularly compelling because it suggests that when tourist activity was high shell abundance decreased.” (p. 6)

In my opinion, the authors specifically flag shell collecting by tourists as a possible causal force in the decline in shell abundance.   It’s of special interest to them, because, as they note, at the beginning of the article,
In particular, the removal of dead shell remains by tourists represents one of the most understudied and least understood processes associated with human activities along marine shorelines.  (p. 1)
And then they add, “[r]igorous assessments of shell removal by tourists are needed . . . .”  (p. 1)  The reader (well, this reader) assumes that what follows in their study is such an assessment of shell collecting.

After laying out the data correlating shell abundance decline and tourism, Kowalewski et al. assert that shell collecting “is an important activity along marine shorelines.”  (p. 7)  To my mind, there’s an implied closing clause to this sentence – “with negative consequences for seashell abundance.”  (Of course, one might ask how we know it’s “an important activity” in this context if, as the authors observe, we don’t really understand it and this study isn’t that missing “rigorous assessment”?)  Beyond mapping the growth in sheer numbers of tourists, Kowalewski and his colleagues didn’t do any study of the collecting or other habits of tourists to this Spanish beach.  Further, with regard to shell collecting on this beach, they note that the shells of the dominant bivalve species here aren’t particularly attractive or desirable to collectors.  (Their lack of research on the tourist-related activities is, I believe, a function of the fact that the project had a different focus for the data gathering.  Only subsequently were the data used to address the ecological issue treated in the report.)

They do list a number of other deleterious activities associated with tourism that might work to reduce the number of shells:  disturbing the sand, gathering of live shellfish, camping, driving recreational vehicles on the beach, and grooming of the beach.

When they state that raking and clearing the sand at Llarga Beach with heavy machinery occurred in the summer months during the 2008-2010 period, but not in the 1978-1981 period, I thought, "Here’s the smoking gun of this story."  Not hard to believe that such grooming is likely to have dire consequences for seashells.

But, at that juncture, the researchers punt when it comes to fingering what tourist-related factors might be most responsible for the shell decline at Llarga Beach.  They write, “The relative importance of these various tourism-related processes is impossible to evaluate for Llarga Beach due to lack of relevant data.”  (p. 7)  So, as far as this analysis is concerned, collecting remains as prominent a possible contributor as beach grooming for the shell decline on this beach.

After reading the research piece, I’m not surprised at how Jason Goldman structured his article on the study for the Washington Post or that, apparently, other news coverage of this study has zeroed in on shell collecting.  It’s the sexy, potential villain in the tale and, it seems to me, as written, the research article, itself, might lead journalists in that direction.

So, I was amused to discover that Michal Kowalewski, in a comment posted on January 15, 2014, on the PLOS ONE website, felt he needed to warn readers about how his study was being misconstrued in the popular press:
Please note that the role of shell collecting is exaggerated in the press coverage, including news reports with titles implying that our paper documents shell loss due to shell collecting.  This is not correct. . . . At this point we lack robust estimates of relative importance played by different tourism-related processes that may be contributing to shell removal or destruction.
Yes, this is a cautionary tale, but one with more messages than I thought at the outset.  One warning directed to us is about reporters and writers with a penchant for "cherry picking" scientific research.  Another concerns the researchers themselves, who should know that they will be cherry picked and write accordingly.

And, finally, I was quite taken with the conclusion Jason Goldman wrote for the Washington Post article in which he quotes geoscientist Karl W. Flessa, who was not involved in this research.  Flessa told him, "I'd rather assume that there are consequences and be proven wrong than the other way around. . . .I'll keep my hands in my pockets the next time I go to the beach."  Maybe I will, too.

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