How climate change is affecting Pacific species

Assessing the vulnerability of marine life to climate change in the Pacific Islands region

Giddens J, Kobayashi DR, Mukai GNM, Asher J, Birkeland C, Fitchett M, et al.

Summarized by Habiba Rabiu, a student of environmental geosciences at Fort Hays State University. Habiba is interested in all aspects of environmental science and conservation & sustainability. She would like to work in educating others about those topics. In her free time, she likes to read, write, and bake.

What data were used? The researchers assessed 83 species grouped into six functional groups based on range size and habitat: pelagic, shark, deep-slope, coastal, coral reef, and invertebrate species. The “coral reef” group of fishes contained many species, so it was further divided into JEGS (Jacks, Emperors, Groupers, Snappers), parrotfishes, surgeon fishes, and “other coral reef” fishes. The species were chosen based on expert opinion, importance of their ecosystem function, records of food fish, and cultural and conservation importance. The species came from a wide range of locations in the Central, West, and South Pacific Ocean. 

To determine the climate change vulnerability of the species, the researchers considered two components: exposure and sensitivity. Exposure was defined as to what degree an organism is likely to experience a negative change in a particular physical variable. Sensitivity was considered a biological trait-based variable, which the researchers determined by review of existing literature and expert opinion. 

Methods: To assess exposure, data from various sources was compiled based on certain variables that were the most significant for species living in the Pacific Islands Region: temperature (surface and bottom), salinity (surface and bottom), ocean acidification (pH), mixed layer depth, precipitation, current velocity, wind stress, surface oxygen, sea level rise, wave height, chlorophyll, and primary productivity. To determine sensitivity, experts were asked to identify the six most important sensitivity attributes for each species out of 12: habitat specificity; prey specificity, complexity in reproductive strategy, sensitivity to ocean acidification, early life history survival and settlement requirements, dispersal of early life stages, sensitivity to temperature, population growth rate, stock size/status, adult mobility, spawning cycle, and other stressors (including habitat degradation, pollution, disease, or changes in the food web). 

For each species, a component score was calculated for both exposure and sensitivity based on the number of factors/attributes that passed a certain threshold. Then, the overall climate change vulnerability rank was calculated by multiplying the exposure and sensitivity component scores. The numerical values for the climate vulnerability rank were the following: 1–3 (low), 4–6 (moderate), 8–9 (high), and 12–16 (very high).

Grid where each square shows what percentage of a species is considered “moderate”, “high”, or “very high” in vulnerability. The squares are shown in greyscale, with 0% being white and 100% being black. Approximate values: Pelagic: 90% moderate, 10% high Shark: 10% moderate, 30% high, 60% very high Deep slope: 60% moderate, 40% high Coastal: 100% moderate Coral reef JEGS: 80% moderate, 20% high Coral reef parrotfish: 60% moderate, 30% high, 10% very high Coral reef surgeonfish: 25% moderate, 75% high “Other” coral reef: 65% moderate, 25% high, 10% very high Invertebrate: 10% moderate, 30% high, 60% very high
The percentage of species within the group that fell within each vulnerability ranking.

Results: All species ranked “very high” in the overall exposure component of vulnerability. It was determined that this was caused by three influences: decrease in oxygen concentration, rise in sea surface temperature, and increase in ocean acidification (decrease in surface pH). In the sensitivity component, it was found that the groups that were made up of larger-bodied species shared similar sensitivity scores, while the groups with smaller and site-attached species tended to differ.

In the overall assessment of climate change vulnerability, the species showed a wide range in vulnerability across the functional groups. The larger and more wide-ranging pelagic and coastal species were scored as the least vulnerable, while the smaller and more site-attached species (small coral reef fishes and invertebrates) were the most vulnerable. Some groups had a more general ranking across all the included species (for example in the coastal group all the species were ranked as “moderate”), while in others there was a wider distribution across vulnerability rankings. 

Why is this study important? Most studies on the effect of climate change of ocean ecosystems focus on a particular or particular type of species, or on singular factors. This study assessed many factors affecting many species, which creates a more all-encompassing view of the effects of climate change and enables focus on the ecosystem as a whole rather than looking at it in pieces. 

The big picture: Well-functioning ocean ecosystems are essential to the health of the planet, but there is still a lack of both information about the ecosystems and the organization and usage of that information. Collecting data on marine species and the environmental factors that affect them (and to what degree) is necessary to their preservation.

Citation: Giddens J, Kobayashi DR, Mukai GNM, Asher J, Birkeland C, Fitchett M, et al. (2022) Assessing the vulnerability of marine life to climate change in the Pacific Islands region. PLoS ONE 17(7): e0270930.

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