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Scientists challenge meaning of biodiversity

The first ever study to go beyond counting species in a given area has revealed new hotspots of marine diversity. The new research challenges conventional wisdom about what biodiversity means.

A new global study of reef fishes, published in Nature today, examines the abundance and characteristics of species and identifies new hotspots of marine life, including the potential for some in the UK. It questions previous thoughts about what constitutes biodiversity and may mean a change of direction for conservation efforts.

Scientists challenge meaning of biodiversity

Scientists challenge meaning of biodiversity

The report, co-authored by scientists at the Universities of Portsmouth and Dundee, presents an alternative view of global biodiversity patterns which reflects ecological processes. It suggests that the most devastating effects of pollution, overfishing and other human pressures may be experienced not in the regions where most conservation efforts are currently concentrated but in areas with fewer species, such as the seas around the UK.

Scientists have long thought that tropical coral reefs, teeming with millions of species, were the areas of greatest biodiversity for fishes and other marine life—and thus most deserving of resources for conservation. Now for the first time scientists have considered global diversity in terms of the characteristics of fish species, rather than simply the number of species present.

The study was carried out by an international team of researchers from Australia, Chile, Indonesia, Italy, Spain, Sweden, the US and the UK. They measured factors other than the traditional species count, such as a species’ role in an ecosystem or the number of individuals of a particular species, revealing new hotspots of biodiversity, including some nutrient-rich, temperate waters.

The results provide new insights into how different fishes associate with each other around the world, and highlight novel and informative ways that diversity information can benefit coastal and fisheries management.

The research team noted how the members of each of these species live, using a detailed matrix of functional traits. These include what the fishes eat (plankton, invertebrates, algae, other fish, or a combination), how they eat it (browsing, scraping, or predation), where they live (in, on, or near the bottom, attached, or free-swimming), whether they are active at night or during the day, and how gregarious they are (solitary, paired, or schooling).

Dr Trevor Willis from the Institute of Marine Sciences at the University of Portsmouth, said “Since the days of Darwin and Linnaeus, the number of different species in an ecosystem—what researchers call ‘species richness’—has dominated the scientific view of global biodiversity patterns and has long been used as a biological basis for management of imperilled ecosystems.

“But just counting species is a very crude way of understanding diversity. By gathering information on the animal’s traits—what they eat, how they move, where they live—we can understand more about how they vary in terms of their function in the operation of natural ecosystems. This functional variation is really the essence of biodiversity.”

Professor Terry Dawson, SAGES Chair in Global Environmental Change at the University of Dundee, said, “Conventional global conservation priority has focused on tropical sites having high biodiversity richness in terms of species.

“In contrast, our research has shown that to maintain healthy resilient marine habitats those regions with fewer species, such as found in the seas around the UK for example, may actually be more vulnerable to catastrophic collapse from human pressures such as pollution and overfishing.”

The information was collected through a ‘citizen science’ initiative developed in Tasmania. As part of the Reef Life Survey program, committed recreational SCUBA divers are trained and supported to survey numbers of reef animals worldwide. Analysis of information provided by Reef Life Survey volunteers over the past six years has revealed new hotspots of marine biodiversity, including south-western Australia and the Galapagos Islands.

The researchers then conducted their study by analysing data from 4,357 standardised surveys at 1,844 coral and rocky reef sites worldwide. The surveys spanned 133 degrees of latitude and found 2,473 different species of fish.

The findings have important implications for planning and management, particularly in regards to the Marine Protected Areas (MPAs).

Lead author, Dr Rick Stuart-Smith of the University of Tasmania’s Institute for Marine and Antarctic Studies, said, “Relatively few MPAs are located at temperate latitudes, particularly in the southern hemisphere, a bias accentuated in recent years with global focus on declaration of large tropical MPAs.

“Our results identify further unrecognised biodiversity value in some temperate and southern hemisphere regions, strengthening the argument for greater representation of these areas in global MPA protection.”

Dr Willis said: “We should perhaps be having a harder look at how well higher latitude marine ecosystems – like around the UK – are being represented by no-take MPAs that enable us to see what relatively natural marine ecosystems should look like.”

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