Quantifying climate change impacts emphasises the importance of managing regional threats in the endangered Yellow-eyed penguin

Abstract

Climate change is a global issue with effects that are difficult to manage at a regional scale. Yet more often than not climate factors are just some of multiple stressors affecting species on a population level. Non-climatic factors-especially those of anthropogenic origins-may play equally important roles with regard to impacts on species and are often more feasible to address. Here we assess the influence of climate change on population trends of the endangered Yellow-eyed penguin (Megadyptes antipodes) over the last 30 years, using a Bayesian model. Sea surface temperature (SST) proved to be the dominating factor influencing survival of both adult birds and fledglings. Increasing SST since the mid-1990s was accompanied by a reduction in survival rates and population decline. The population model showed that 33% of the variation in population numbers could be explained by SST alone, significantly increasing pressure on the penguin population. Consequently, the population becomes less resilient to non-climate related impacts, such as fisheries interactions, habitat degradation and human disturbance. However, the extent of the contribution of these factors to declining population trends is extremely difficult to assess principally due to the absence of quantifiable data, creating a discussion bias towards climate variables, and effectively distracting from non-climate factors that can be managed on a regional scale to ensure the viability of the population.

Tangled and drowned: a global review of penguin bycatch in fisheries

“…Two of these birds were caught off the Waitaki River Mouth, 1 off Kaka Point and another off Stewart Island. Given the species' precarious situation, with low numbers (216 breeding pairs on the New Zealand South Island in 2015−16) and an overall decreasing population at previous strongholds (76% decline be tween 1996 and 2016; Ellenberg & Mattern 2012, Mattern et al 2017, the effects of gillnet bycatch on the species may be significant and merits closer examination.…”

“…However, given limited available conservation resources, some comparison gives context and aids prioritisation. Climate change is likely to affect all of these species, albeit in different ways (García-Borboroglu & Boersma 2013, Trathan et al 2015, Mattern et al 2017. In order to improve resilience of penguin populations in the face of climate change, other threats need to be substantially reduced, and incidental mortality in fishing gear is one threat that can be addressed immediately.…”

“…As many vessels use this gear within the Humboldt penguin foraging range (Goya et al 2011), the region is clearly a priority for further research and mitigation, in association with ecosystem-based management of the anchoveta fishery and ensuring that tourism is carefully managed at colonies. The situation is complex for yellow-eyed penguins; the population is small and decreasing, and is facing a wide spectrum of threats , Mattern et al 2017, including sensitivity to human disturbance , vulnerability to disease outbreaks and marine pollution, the loss of mature coastal forest as breeding habitat, and predation by introduced mammals . Furthermore, recent research shows that as sedentary benthic foragers, yellow-eyed penguins are particularly vulnerable to climate change (Mattern et al 2017).…”

“…The situation is complex for yellow-eyed penguins; the population is small and decreasing, and is facing a wide spectrum of threats , Mattern et al 2017, including sensitivity to human disturbance , vulnerability to disease outbreaks and marine pollution, the loss of mature coastal forest as breeding habitat, and predation by introduced mammals . Furthermore, recent research shows that as sedentary benthic foragers, yellow-eyed penguins are particularly vulnerable to climate change (Mattern et al 2017).…”

“…Bycatch mortality is of greatest concern for the Endangered yellow-eyed penguin (Darby & Dawson 2000, Ellenberg & Mattern 2012, Mattern et al 2017). The population is decreasing and is now thought to number fewer than 400 pairs for the New Zealand mainland population (only 216 nests found during 2015/16 searches; M. Young pers.…”