Quantifying climate change impacts emphasises the importance of managing regional threats in an endangered species

Abstract

As a global issue the effects of climate change are difficult to manage on a region scale. However, more often than not it is only one of many problems that need to be addressed in species conservation. Non-climatic factors - especially those of anthropogenic origins - play equally if not more important roles with regards to population developments of species and often provide much better toeholds for conservation activities. We examined the population trends of the endangered Yellow-eyed penguin (Megadyptes antipodes) in New Zealand using monitoring data dating back to the 1980s. We developed a Bayesian population model incorporating various climatic factors to assess the relative influence of climate change on the penguin numbers over the past 30 years. Sea surface temperature (SST) proved to be the dominating factor influencing survival of both adult birds and fledglings. Increasing SST since the mid-1990s went along with 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 nonclimate related impacts, such as fisheries interactions, habitat degradation and human disturbance. But their exact contribution towards population trends is extremely difficult to assess principally due to the absence of quantifiable data. This potentially creates an analysis bias towards climate variables, effectively distracting from non-climate factors that can be managed on a regional scale to ensure the viability of the population.