A study recently published in Nature may seriously influence future conservation priorities in marine systems.
Species richness, the number of different species in an ecosystem, was for a long time the predominant measure of global biodiversity. This is now changing rapidly as researchers are realizing that rather than considering the sheer number of species, it is which specific species that are present that is crucial for ecological functions.
Qualities rather than quantities
According to the study, the characteristics of the species present and the number of individuals in each species are crucial parts of determining the nature and the strength of the relationship between species diversity and a range of different ecological functions.
"Different species do not contribute in the same way to different processes in an ecosystem, so there is a need to look at more than simply the number of species that are present in a system if we are interested in the sustainability and resilience of the processes," explains centre researcher and co-author Stuart Kinninmonth. He is is a spatial ecologist, specialising in how social and ecological systems are networked.
"By looking at the species traits and behaviours, how they eat, where they move and so on, we get a better idea of their function, and about the diversity of functions that they have,"
Stuart Kinnimonth, co-author
A new playing field
The authors argue that integrating this into global assessments, rather than relying on species counts, should provide a more relevant representation of global biodiversity patterns when it comes to ecological functions.
The study is the first of its kind, and covers large parts of the globe. The authors have looked at data from 1844 sites with quantitative assessments of 2473 marine reef fish species, covering 133 degrees of latitude and includes all ocean basins.
The authors compare a traditional measure of biodiversity with their metric, including function and abundance of species and identify new biodiversity hotspots, both in tropical and temperate regions.
The results show that in tropical regions, where there are many different species present, each species contribute proportionally less to the ecosystem functions than in temperate region, where fewer species are present.
Keeping the score
"Coral reefs have many different species present, but many of them do the same thing and have the same function. In other systems, such as the Galapagos, the number of species is substantially lower, but the functional diversity is still very high," says Kinninmonth.
In other words, while coral reefs are still the most species rich marine systems, the study shows that other areas can have a higher diversity when it comes to functions.
These findings have important implications for marine policy and planning. Most of the protected areas are today located in tropical regions where the species count is high. Taking function into the equation however, changes the motivation of protection and conservation.
"In a system where there are few species and each one plays a unique roll and has a unique function, the loss of a species may have more severe consequences than in a system where many different species have the same function. This means that there is a kind of biodiversity value that we haven not fully considered before," says Kinninmonth.
"This strengthens the argument for expanding the protection of certain systems, that have previously not been considered in this way," he concludes.
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