A new review published in Ecology Letters, a peer-reviewed scientific journal, assessed seabird and marine mammals’ responses to climate change and climate variability. Researchers based their analysis on data from more than 480 preexisting studies and found that “the likelihood of concluding that climate change had an impact [on either marine mammals sea birds] increased with study duration”. In other words, studies that include data from longer lengths of time are going to be most useful for measuring climate change’s effects on the observed species.
Research Method and Design
From the 484 peer-reviewed studies that matched the researcher’s inclusion criterion, 2,215 observations were compiled into a database and mapped. This includes 1,685 observations for seabirds and 530 observations for marine mammals. 54% of observations for seabirds were distributed towards the northern hemisphere (39% of observations from temperate and polar regions). For marine mammals, 83% of observations were distributed toward the northern hemisphere (53% of observations from temperate and polar regions). For both seabirds and marine mammals, tropical and subtropical regions represented a mere 8% of total observations.
Authors of the preexisting studies found 38% of total observations to be related to climate change, 49% were attributed to climate variability, and 13% were attributed to both. Climate change refers to the long-term changes in weather patterns, typically over decades or longer, while climate variability is usually thought of as day-to-day shifts in weather.
According to the new review, “a significant majority of observations concluded that climate change had an effect on both the seabird and marine mammal groups across all the response classes”. Response classes include demography, distribution, condition, phenology, behavior, and diet. The analysis also states that species that had more limited temperature tolerance ranges and relatively long generation times were reported to be most affected by changes in climate. Generation times are temporal intervals between the birth of an individual organism and the birth of its offspring.
The longer the duration of the original studies, the more likely authors were to infer that the observed changes in taxonomic groups were due to climate change rather than climate variability. 189 of the preexisting studies (669 observations) that demonstrated climate change effects had a time span above the estimated average threshold of 19 years. Generally, studies on marine mammals were able to demonstrate climate change responses based on shorter time scales (17± 5 years) versus seabirds (22 ± 3 years).