Seafood Extinction Risk: Marine Bivalves in Peril?
Boulder, Colo., USA: Marine bivalves are an important component of our
global fishery, with over 500 species harvested for food and other uses.
Our understanding of their potential vulnerability to extinction lags
behind evaluation of freshwater bivalves or marine vertebrates, and so Shan
Huang and colleagues, in analyses presented at the annual meeting of the
Geological Society of America, used insights and data from the fossil
record to assess extinction risk in this economically and ecologically
important group. Their findings suggest that among all today’s
shallow-marine bivalves (~6,000 species), harvested species tend to be
widespread along major coastlines and are able to tolerate wide ranges of
environmental conditions (e.g. sea-surface temperature). This is good news,
they note, because the fossil record shows that these broad ranges can help
them survive “mild” changes in the environment.
Because little is known about the direct human impact on these harvested
species, this study by Huang and colleagues studied species’ intrinsic risk
of extinction, laying the groundwork for efficiently managing these natural
resources and conserving marine biodiversity. Having confirmed the ability
of their method to predict how intrinsic characteristics interact with
external pressures to yield high extinction rates in the past, the next
step will be to estimate extinction risk in the future bivalve population.
This goal highlights the urgent need for more complete data on the capture
and harvesting of these bivalves, which would enable a comprehensive
investigation on the direct effects of exploitation.
Overall, this study by Huang and colleagues showcases an integrative
approach of combining paleontology and biogeography to study species’
intrinsic risk of extinction, which is essential to efficiently managing
our natural resources and conserving biodiversity.
Q: What kind of bivalves are you talking about here? How does this
relate to what people are eating?
A: We studied all bivalve species that live in the sea from the shoreline
to 200 meters deep (most bivalves living deeper than this aren’t readily
harvested). We find that only 500+ of almost 6,000 marine bivalve species
are harvested, but we were surprised to find that many of those species
come from evolutionary groups outside the ones we commonly eat—mussels,
oysters, scallops, and cockles. People also use bivalves as sources of
pearls, a kind of “silk” that can be woven into cloth, and even
windowpanes!
Q: Does human consumption contribute to them being in peril, or is it
changes to the environment?
A: Previous studies of marine fish have shown that a combination of human
harvesting and climate change is negatively impacting a number of species
and that such declines depend in part on the biological attributes of
individual species. Comparable analyses are lacking for shellfish despite
their biological and economic importance. In fact, global catch data are
available for only a very small proportion of harvested bivalves. So in
this study, we used the fossil record and today’s geographic distribution
of species to identify the harvested bivalves that are intrinsically more
prone to extinctions. We found that many of the evolutionary lineages
(here, taxonomic families) containing harvested bivalves were subject to
high extinction rates during the past 65 million years. On the other hand,
many of the harvested species within those lineages are sufficiently
widespread today, suggesting that, all things being equal, they should be
fairly extinction-resistant. But we urgently need more information on the
extrinsic pressures being applied to those species -- global catch,
pollution, and regional climate changes, to determine their future
vulnerabilities. This finding calls for further investigation on how
external pressures have interacted with family-specific characteristics to
yield high extinction rates in the past, which could improve estimates of
extinction risk in bivalves, particularly those of economic value.
Q: How does the fossil record tell us about the future of marine
bivalves?
A: All bivalve lineages at the taxonomic level of families, including the
harvested ones, have been around for tens of million years, and their
evolutionary history is preserved in a rich fossil record. From this
history, we can see that some families tended to have, on average, higher
extinction rates throughout the last 65 million years. This suggests that
these families might have biological properties that made them more
extinction-prone, although we do not yet always know the immediate causes
of these extinctions. The PERIL metric incorporates this information into
an estimate of intrinsic extinction risk, and we were encouraged to find
that this relatively simple metric successfully predicted extinctions over
the past five million years in two regions with especially well-studied
fossil records. Putting modern seafood bivalves into this historical
framework, including their family-specific risk, gives us a better-informed
estimate of their relative robustness to external pressures.
Talk:
Seafood Extinction Risk Estimated from Biogeography and the Fossil
Record: Marine Bivalves in Peril
D16: 196-6: Thursday, 29 Oct., 2:50 p.m. EDT, Geological Society of America
2020 Connects Online,
https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/353217
Shan Huang, Stewart M. Edie, Katie S. Collins, Nick M. Crouch, Kaustuv Roy,
and David Jablonski.
CONTACT: Shan Huang: shan.huang@senckenberg.de
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