Bog Fritillary Butterfly
It’s a well-known fact: global warming is an impending problem, and as each day passes, we’re growing closer and closer to facing its consequences. One of the major effects climate change will have in the future is on biodiversity, or the variety of life forms in the world. Many scientists have already studied the effects that global warming will have on certain species. However, a new study by a research team from Université Catholique de Louvain in Belgium, published in Journal of Animal Ecology, suggests that the way global warming’s effects on species were measured in previous studies may have left much room for error, and that the threat to biodiversity may be more serious than previously thought.
The ideal animals to observe when studying the effects of climate change are ectotherms, or animals dependent on external sources for heat. For this reason, butterflies have been used in previous studies to find out how an increase in temperature will affect their species in the future. However, these studies restricted their experiments to a single butterfly life stage, and in terms of population viability, past studies only observed a yearly population growth rate. These techniques make it nearly impossible for biologists to properly examine the effect that climate change will have on butterflies, especially since climate change occurs during some seasons, and can vary throughout the year.
Trying to avoid these shortcomings, the recent study by PhD graduate students Viktoriia Radchuk and Camille Turlure under the supervision of Dr. Nicolas Schtickzelle, lecturer at Université Catholique de Louvain, sought to see the effects that a temperature rise would have on each life stage of the Bog Fritillary butterfly, rather than focusing on a single stage. Furthermore, data was collected every month during a series of several months, giving a better picture of how climate change during each season would affect the butterfly population.
In the study, the research team conducted several laboratory and field experiments in order to predict the survival of the butterflies under many different scenarios of climate change, and to see how those scenarios would affect each life stage of the butterflies. These scenarios included a baseline scenario, which represented the current climate, an increased temperature scenario, an increased temperature variability scenario during certain months, and a European climate change scenario, which is a likely projection for Europe’s climate according to the Intergovernmental Panel on Climate Change report. The Belgian duo tested the influences of these scenarios on the butterflies by observing their effects through the course of several months on the number of eggs laid by female butterflies, the eggs’ survival, pupa survival, and the larva survival when passing through winter (‘overwintering’).
The results of the experiment showed that the number of eggs laid by the female butterflies, egg survival, and pupa survival increased in all of the temperature scenarios. However, because of a warmer winter, the overwintering larvae were more vulnerable to diseases and fungal infections, thereby decreasing larva survival. Using a model, the Belgian team calculated how the impacts on these individual life stages would affect the overall population. The model showed that although most of the life stages hinted at an increased population with higher temperatures, the life stage that determined population viability was the overwintering larva stage. This stage was negatively affected by all of the climate change scenarios, and resulted in (compared to the baseline scenario) an 88% butterfly population reduction in the increased temperature variability scenario, a 94% reduction in the temperature increase scenario, and a 97% reduction in the European climate change scenario. These results suggest that because temperature increases will negatively impact the overwintering stage of the butterfly life cycle, the most temperature-sensitive life stage, the overall population of butterflies will decrease significantly in the coming years due to climate change.
This study, though significant in terms of butterfly survival in the future, is also pivotal because it points out some major flaws in how conservation guidelines were previously constructed. The results show that only after thoroughly examining each stage of animal life cycles through the course of several months can we properly assign conservation guidelines in the context of climate change and global warming. The results of this study prove just how important it is to examine the entire life cycle of animals in order to make accurate predictions on how climate change will affect animal populations in the future.
The study also sheds light on how conservation guidelines should be constructed. The Belgian research team, in light of their findings, believe that the best way to approach climate change’s effect on organisms would be by using a resource-based habitat view, which defines a habitat as a collection of resources needed for all of a species’ life stages. The development of more meaningful population analysis and conservation guidelines would give not only a more accurate depiction of the future, but would also provide us with more clues as to how to we can protect biodiversity from burning away with global warming.
Radchuk, V., Turlure, C., and Schtickzelle, N. (2012), Each life stage matters: the importance of assessing the response to climate change over the complete life cycle in butterflies. Journal of Animal Ecology. Published online 24 Aug 2012. DOI: 10.1111/j.1365-2656.2012.02029.x