Western University BiologyWestern Science

What are butterflies telling us about global warming?

By Aniruddho Chokroborty Hoque

describe image

Parnassius smintheus

Butterflies have often rescued us when we've been in want of that certain sublimity of expression. As if metaphorical wings would convey a feeling with a little more grace or help float an awkward idea on a cushion of air. Take the familiarity of getting butterflies in the stomach when talking to a crush. Or the majesty of Mohammed Ali's boxing prowess being described as, "he flies like a butterfly, stings like a bee." To mathematicians, weird and unpredictable events are akin to a butterfly flapping its wings in New Mexico causing a hurricane in the Indian Ocean. Then there are biologists like Dr. Nusha Keyghobadi. A professor at the University of Western Ontario, she has been studying the diminutive butterfly for over fifteen years, trying to fathom the complex phenomenon of global warming. As an explorer standing at the crossroads of genetics and ecology, she is studying how extreme temperature changes and habitat loss affect butterflies in order to answer a key question: just how well suited is nature and the wildlife around us to cope with the consequences of global warming?

            Butterflies can provide crucial eco-services, such as pollination. The value of butterfly and insect pollination to Canadian agriculture has been estimated at a billion dollars. Pollination is essential for the survival of plants, which happen to be the primary food source for animals. Indirectly, the humble butterfly supports a range of predators and is a crucial element of the food chain atop which the bigger animals purportedly rule. Butterflies are also considered by many to be important indicators of ecosystem health. The responses of butterflies to environmental changes, such as global warming, are likely to occur in other insects and wildlife, and drastic falls in butterfly populations could signal a disruption of critical ecosystem services. Given the increasing effects of global warming, that possibility seems closer than ever before. 

            Dr. Keyghobadi studies the Rocky Mountain Parnassian (Parnassius smintheus), the most common high altitude butterfly species in Kananaskis Country, Alberta, Canada. Every year, during the two summer months when the butterflies emerge, colleagues of Dr. Keyghobadi, specifically Dr. Steve Matter (University of Cincinnati) and Dr. Jens Roland (University of Alberta) and their students go out to the field counting their numbers, tracking the distance they fly between and around their habitats and collect the genetic data of these butterflies. The study site is close to the field station run by the BioGeoScience Institute (University of Calgary), which has tracked weather patterns, temperature changes and land area around that region for the past twenty years. "I initially studied this eco-system during my Ph.D. at the University of Alberta. Back then, the analysis of multiple datasets and genetic data wasn't as sophisticated as it is now," observes Dr. Keyghobadi. After taking a long hiatus from her Ph.D. research topic and branching into other study areas, she has gone back to her roots armed with newer tools and techniques. Dr. Keyghobadi is also harnessing the power of young and curious minds. As a part of an online global network of ecology professors teaching landscape genetics, she has been working with a group of graduate students from Canada and North America. Dr. Keyghobadi's latest paper features significant contributions from these students who worked with her as a part of their graduate coursework. "It is important that students have access to knowledge, are aware of pressing global concerns and can acquire expertise in dealing with them."

            A major part of Dr. Keyghobadi's research has focused on understanding how habitat loss and declining populations affect the genetic diversity of the Rocky Mountain Parnassian. Mother Nature has regularly thrown a veritable shopping list of monkey-wrenches at the Rocky Mountain Parnassian. Bad weather, disease-causing parasites, irregular food availability, and forest fires have all been on the menu and the Rocky Mountain Parnassian has tasted and sampled them all. The Parnassian's ability to adapt and survive under such unfavourable conditions may be attributed to their genetic diversity. Genes, as blocks of DNA, function as units of information that confer some sort of skill or property to the organism that they are a part of. While some genes may influence the colour patterns of a butterfly's wing, others help the Parnassian tackle extreme heat or cold. For a group of organisms, a myriad collection of genes enables them to cope with and adapt to ever-changing environmental conditions around them and is essential for their continued survival. Too little of it can be harmful and potentially fatal in the long-term. With the loss of raw genetic material, populations lose the ability to adapt to new environmental conditions akin to the majority of a hockey team being out of commission due to injuries. A hockey team with a diverse roster of players and playing strategies would have a better shot at the Stanley Cup compared to a small team with a limited repertoire of players and play strategies. It is this genetic diversity that has enabled the Rocky Mountain Parnassian to successfully tackle, in John Keat's own words, "nature's law, not force".

            In the past few decades however, mankind's activities have introduced extreme environmental variables that have sent the Parnassian population scrambling. The Rocky Mountain Parnassian lives in small clusters scattered amongst a patchwork of high-altitude meadows just above forest tree-lines. Due to rising temperatures, tree-lines have been slowly moving up towards cooler altitudes and encroaching into these meadows. Over the years, this process has slowly fragmented and destroyed the habitats of these butterflies. Additionally, in a stark reminder of the effects of global warming, extreme temperature changes in the Kananaskis winter of 2002-2003 resulted in a severe population collapse of the Rocky Mountain Parnassian with more than sixty-percent mortality. Dr. Keyghobadi and her team compared the Parnassian butterflies using population numbers and genetic information collected from these butterflies in 1995 and 2004-5, two years after the severe population collapse.

            What she found is profoundly revealing in two ways. Firstly, there has been no loss of overall genetic diversity within the Parnassian population. The inter-connectedness and short distances between these meadows allow for constant movement between local butterfly clusters. This enables the Parnassian population as a whole to preserve and maintain genetic diversity. The butterfly's movements across the meadows is essential in restoring and maintaining the genetic diversity. That the butterflies have re-established the original genetic diversity after a severe population collapse is a testament to the resilience that is Life. It yearns for balance and at every step attempts to minimize the damage done. Life, however, has its limits and mankind's activities for the past few decades have been straining against that precarious upper limit. The painstaking data on weather patterns and land area that has been collected over the decades points to an increasing trend of habitat erosion and severe temperature changes in the Kananaskis Country region. It is the close proximity of the meadows that has facilitated migration over small distances enabling the butterflies to restore and maintain genetic diversity. It is highly probably that with increased habitat loss, the distances between meadows would increase. Extreme winters may result in another occurrence of a drastic population collapse. The Parnassian population, unable to cope with these severities, might never repopulate completely and consequently reach the same level of genetic diversity ever gain.

            Dr. Keyghobadi's work is an unerring bellwether for global warming research. But why dedicate one's entire academic career studying butterflies to understand global warming when, for example, the majesty of the polar bear or the dignified regality of the grey wolf has reaped visibly ongoing and concerted efforts to save them and their habitats from global warming? "Polar bears for example, have relatively long life-spans of around thirty years, compared to the butterfly's one. Tracking butterflies is also far more manageable than polar bears who tend to have huge home-ranges. The pattern of declining populations and the loss of habitat is a world-wide phenomenon affecting all species. The study-site in Kananaskis has a perfect combination of factors, enabling us to ask difficult questions in a highly tractable environment", Dr. Keyghobadi explains.

            Essentially, she is asking the same questions on a far more manageable scale, spending less money and resources collecting data and more time analyzing it. Her work with the unassuming, unostentatious Rocky Mountain Parnassian has provided us with front-row seats, showing us what is actually happening and gives us an idea of where we're headed to. Nature is resilient, but resilience has its limits. Think back to our fatigued hockey team. They've been in the game too long, accumulating injuries and the wear and tear. They're down but not out. All they need is a break, a moment or two of respite, some time to recuperate. Dr. Keyghobadi and her colleagues are sitting on at least twenty years worth of data with information on the genetic make-up of butterflies, weather patterns and population numbers and they don’t plan to stop collecting these numbers any time soon. Armed with her network of students and newer, more powerful analytical tools, she is sifting through trends and looking for patterns to make us better informed global citizens. Her research is going to be the needle that points North, guiding future generations of scientists to help make this world a better place.

-The butterfly counts not months but moments, and has time enough.

Rabindranath Tagore

Aniruddho Chokroborty Hoque, a PhD candidate in Shiva Singhs lab, is the graduate student science communications liaison officer for the Biology Department. This article resulted from a science-writing internship with Prof. David Smith.