Embargo: April 5th at 5pm Eastern Time
World`s reef fishes tussling with human overpopulation
Scientists studied the global influence of human population on corals reefs and were surprised to find that highly
diverse reef fish systems are the most vulnerable to human threats
In an unprecedented collaborative analysis published in the journal PlosBiology, scientists from 49 nations
demonstrated that the ability of reef fish systems to produce goods and services to humanity increases rapidly with
the number of species. However, growing human populations hamper the ability of reefs to function normally, and
counterintuitively, the most diverse reef fish systems suffer the greatest impairments from stressors triggered by
human populations. The study documented that the extent of this distress is widespread and likely to worsen because
75% of the world`s reefs are near human settlements and because around 82% of the tropical countries with coral
reefs could double their human populations within the next 50 to 100 years.
“Coral reefs provide a range of critical goods and services to humanity—everything from nutrient cycling to food
production to coast protection to economic revenues through tourism,” says Camilo Mora at Dalhousie University
and lead researcher of the study. “Yet the complex nature and large-scale distribution of coral reefs is challenging
scientists to understand if this natural ecosystem will continue working to deliver goods and services given the
ongoing loss of biodiversity in coral reefs.”
“Numerous experiments have showed that biodiversity has positive effects on several ecosystem processes, although
the number of species required to ensure the functionality of a given process is fairly low, as many species often
have similar ecological roles,” says Michel Loreau from McGill University, a co-author of the study. “What remains
largely unknown, however, is whether the results of experimental studies reflect what happens in real ecosystems.”
To fill this unknown, 55 researchers, in a two-year
study, collected the necessary data to determine
whether biodiversity influences the efficiency of
reef fish systems to produce biomass, and if so,
elucidate the role of humans in such a linkage. The
team collected demographic data on human
populations as well as environmental and
biological data on the identity of species, their
abundances and body sizes in almost two thousand
coral reef locations worldwide. The data on
abundance and body size were used to calculate
the cumulative weight of all fishes on each reef
(also called standing biomass), which is one of the
main services reef fishes provide to humanity
through food supply but also a very close proxy for
how effectively ecosystems produce biomass.
Relationship between biodiversity and function. The plot on the left indicates
the frequent pattern between biodiversity and function observed in experimental
studies. The plot on the right shows the pattern observed for coral reefs in this
study. Figures elucidate the slopes documented in the PlosBiology paper.
“The results of the study were stunning,” says co-author Kevin Gaston at Sheffield University. “While experimental
studies have elucidated that the biomass production of ecosystems stabilizes after a certain number of species is
reached, this field study demonstrated that the production of biomass in reef fish systems did not saturate with the
addition of new species.”
“This study shows, quite simply, that the more biodiversity, the better,” says co-author Marah Hardt with OceanInk.
“The benefits appear limitless, if we allow ecosystems to operate at their full potential.”
“The reasons leading to a non-saturating relationship between diversity and
biomass production are intriguing,” says coauthor Michel Kulbicki at the French
Institute for Research and Development. “Nevertheless, this strong relationship
clearly indicates that species interact in such a way that their combined effect is
larger than the addition of their individual parts and that the loss of species can
have far-reaching consequences in the functioning of coral reefs.”
The study also demonstrated that standing biomass reduced with increasing
human density, although for the same number of people the reduction of
biomass was significantly larger in more diverse ecosystems. The authors
presume that the stronger deleterious effect of humanity on more diverse reefs is
due to the selective extirpation of large fishes, which are often more efficient at
turning food into biomass and lack competitors precluding their ecological
replacement by other species.
“It’s been usual to expect that diverse ecosystems could lose a few species
without it mattering very much because the high redundancy of species should
allow to replace any species that is lost,” said Peter F. Sale, assistant director of
the Institute for Water, Environment and Health of the United Nations
University, who was not involved in the study. “The results of this study now
suggest that we do not have such insurance and that reef ecosystems are at
greater risk from human pressures than we previously thought.”
The top plot shows the modeled interlink
among biodiversity, function and human
density. The bottom plot shows the current
and expected distribution of the world’s
coral reefs related to nearby human
density. Figures modified from the
PlosBiology paper.
The study documented that the deleterious effect of humanity on reef fish
systems can be widespread, as some 75% of the world’s coral reefs are near human settlements and could worsen, as
82% of countries with coral reefs are expected to double their human populations within the next 50 to 100 years.
“Human overpopulation is a very sensitive topic across endeavors from science to religion and politics,” Mora says.
“Unfortunately, we find again and again that our global population cannot be sustainably supported without the
deterioration of the world’s natural resources and the resulting backlash on human welfare. Thus, identifying
socially and politically acceptable solutions to curb human population growth is at the core of finding ultimate
solutions for the protection of biodiversity and the prevention of unnecessary hardship.”
“We found that dense human populations were associated with heavy overfishing, land use, and coastal
development,” says coauthor David Booth at the University of Technology, Sydney. “This highlights the challenge
behind the management required to adequately protect coral reefs and the need to focus on alternative economic and
policy tools that address the root drivers of reef degradation.”
Coral reefs worldwide are slowly being degraded due to an increasing human population and resulting threats from coastal
development, fishing, pollution, and agricultural land use. Without immediate international attention, coral reefs may soon be
beyond repair. Photos by Humberto Bahena and Henry Wolcott, Mark Defeo, Tyler Smith, Steve Spring, Stephen McGowan from
Marine Photobank. Photos for articles covering this story are available at: www.fmap.dal.ca/pressmaterial.php
“This is a critical situation,” says coauthor Sebastian Ferse from the Leibniz Center of Tropical Marine Ecology. “It
underlines once again that current management approaches are insufficient to protect marine biodiversity on a large
scale, and that holistic approaches combining natural and social systems are needed.”
“Not everything was doom and gloom,” says coauthor Maria Beger at the University of Queensland. The study
reported that at least 25% of the world’s reefs remain distant from direct human effects. Those reefs are located on
small and isolated areas where human habitation is harsh. “These few reefs are in stark contrast with degraded sites,
and may still be able to act as sources to replenish others. This is a fortunate situation that can buy us some time
while we figure out effective solutions to this coral reef crisis,” she adds.
“Coral reefs are the most diverse ecosystem on the planet, hosting thousands of species and generating numerous
goods and services to millions of people worldwide,” says Enric Sala, a National Geographic fellow and co-author
of the study. “The future of coral reefs and the services they provide to a growing human population depend on how
soon countries become seriously committed to regulating human threats.”
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Citation: Mora C, Aburto-Oropeza O, Ayala Bocos A, Ayotte PM, Banks S, Bauman AG, Beger M, Bessudo S, Booth DJ, Brokovich E, Brooks A, Chabanet P,
Cinner JE, Cortes J, Cruz-Motta JJ, Cupul Magana A, DeMartini EE, Edgar GJ, Feary DA, Ferse SCA, Friedlander AM, Gaston KJ, Gough C, Graham NAJ,
Green A, Guzman H, Hardt M, Kulbicki M, Letourneur Y, Lopez Perez A, Loreau M, Loya Y, Martinez C, Mascarenas-Osorio I, Morove T, Nadon MO,
Nakamura Y, Paredes G, Polunin NVC, Pratchett MS, Reyes Bonilla H, Rivera F, Sala E, Sandin SA, Soler G, Stuart-Smith R, Tessier E, Tittensor DP, Tupper
M, Usseglio P, Vigliola L, Wantiez L, Williams I, Wilson SK, Zapata FA (2011) Global Human Footprint on the Linkage between Biodiversity and Ecosystem
Functioning in Reef Fishes. PLoS Biol 9(4): e1000606. doi:10.1371/journal.pbio.1000606
The paper is freely available at: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.1000606
The study was funded by the Sloan Foundation through the Census of Marine Life’s Future of Marine Animal Populations and Natural Geography in Shore
Areas projects, the Royal Society, the Leverhulme Trust, Nakheel PJSC, the Gordon and Betty Moore Foundation, Galapagos National Park Service, Charles
Darwin Foundation, Conservation International, Walton Family Foundation, the Australian Research Council, National Geographic, the Western Indian Ocean
Marine Science Association, the German National Academic Foundation, the Coral Reef Conservation Program of the National Oceanic and Atmospheric
Administration, The National Marine Fisheries Service Office of Habitat Conservation, the 21st Century Centers of Excellence Program of the Japan Society
for the Promotion of Science, the French Institute for Biodiversity, the David and Lucile Packard Foundation, the Wildlife Conservation Society, the United
States National Science Foundation’s Long-term Ecological Research Program, The Conservation Leadership Programme, Australian Institute of Marine
Sciences, the Australian Department of Environment, Water, Heritage and the Arts, The Marisla Foundation Environment Program, the World Wildlife Fund,
The Ocean Conservancy, The French Institute for Research and Development and the Natural Sciences and Engineering Council of Canada.
Enquires for specific countries or regions can be made to specific authors, whose countries and regions are outlined at:
www.fmap.dal.ca/pressmaterial.php
Below is the contact information of authors for general enquires:
Camilo Mora, Ph.D.
Dalhousie University, Halifax, NS
Canada-USA-Colombia
Email: cmora@dal.ca
Available in Colombia at:
Phone: country code: 57, Code provider: 313, Phone: 776 2282
From the USA or Canada dial 011 57 313 776 2282
English-Spanish
Michel Loreau, Ph.D.
Kevin J. Gaston, Ph.D.
Michel Kulbicki, Ph.D.
French-English
Department of Biology, McGill University
Montreal, Canada.
Email: michel.loreau@mcgill.ca
Phone: 1 (514) 398-3778
English
Biodiversity and Macroecology Group, Department of
Animal and Plant Sciences, University of Sheffield,
United Kingdom.
Email: k.j.gaston@sheffield.ac.uk
Phone: 0114 222 0030
French-English
Institut de Recherche pour le Développement
France-French Overseas Territories
Email: michel.kulbicki@ird.fr
Phone: +33 4 40 19 24 17
David Booth, Ph.D.
Laurent Wantiez, Ph.D.
Maria Beger, Ph.D.
English
Univ. of Technology
Sydney, Australia
Email: David.Booth@uts.edu.au
Phone: +61 2 9514 4053
French-English
Laboratoire LIVE, Université de la Nouvelle-Calédonie.
Aquarium des Lagons,
Nouméa cedex, New Caledonia.
Email: laurent.wantiez@univ-nc.nc
Phone: +687 290380
German-English
Commonwealth Centre for Applied Environmental
Decision Analysis, University of Queensland, Australia
Email: m.beger@uq.edu.au
Phone: +61 4 17593080
Octavio Aburto-Oropeza, Ph.D.
Hector M. Guzman, Ph.D.
Spanish-English
Scripps Institution of Oceanography
USA-Mexico
Email: octavioaburto@gmail.com
Phone: +1-619-985-9945
Spanish-English
Smithsonian Institute English-Spanish
Panama
Email: guzmanh@si.edu
Phone: (00507) 6618-8406
Contact for External Comments
Peter F. Sale, Ph.D.
United Nations University
Canada
Email: sale@uwindsor.ca
Phone: +1 705 764 3359