“The amount of climate change that we would observe in our lifetime isn’t very great so to understand a larger magnitude of change, you really have to look at longer records.” To the average fisherman, the mosquito-like midge – formally known as the chironomid – serves as an essential component to any well-equipped tackle box. Their plentiful numbers, which disperse most prominently near or along lakes, make them a favourite food source for a variety of freshwater fish. But to Dr. Ian R. Walker, Professor at UBC Okanagan’s Irving K. Barber School of Arts and Sciences, chironomids are more than just ample bait for hooking the perfect line. Scattered near the bottom of lakes and streams, their fossilized remains, preserved from thousands even millions of years ago, tell untold stories of past environmental conditions and potentially hold clues for predicting future climate change. “We rely on looking at paleoenvironmental evidence of how climate has changed to get a better perspective on how climate change has occurred in the past to then understand how it might shift in the future,” Walker says. “The amount of climate change that we would observe in our lifetime isn’t very great so to understand a larger magnitude of change, you really have to look at longer records.” Walker has dedicated nearly 25 years to investigating what secrets chironomids reveal about glacial and post-glacial environments throughout the millennia. Because their number, type and distribution are directly affected by climate changes, the larvae of chironomids are good indicators of a location’s temperature and climate. Lake sediments accumulate at a rate of about half a metre every 1,000 years, allowing the remains to preserve at an astonishing rate. Equipped with this knowledge, Walker realized early on in his academic career that mining the head parts of chironomids from core samples taken from lake bottoms could provide significant insight into climate change patterns. “I suggested one day that it would be interesting to take a core of a lake in order to analyze the remains of these insects and get an idea of how the lake had changed over time,” says Walker. “I started comparing results that I got in BC with results in New Brunswick and found that there were a lot of features in common during the period immediately following de-glaciation. It made me think of the potential relationship between these insects and climate.” What Walker found buried within the lake cores he sampled began to weave a complex tale of the climate and habitat of the living beings that inhabited the location thousands of years ago. The Okanagan Valley, where he has chosen to focus his work, has proven ripe for well-preserved midge remains due to its large diversity of lakes, which vary not only in size but also in salinity. The elevation gradients of the Okanagan’s mountains also provide generous amounts of variation in the patterns of insect distribution. In studying the midges, Walker was able to develop a mathematical
model that has the ability to assess quantitatively what the climate had been like at various times in the past. Among his discoveries are that temperatures at the end of the last glaciation (prior to 9,000 BC) were two degrees Celsius colder than now. Walker says his chironomid paleoecology research has also revealed that from about 9,000 to 6,000 BC, summer temperatures were two to three degrees warmer than today. Temperatures have been comparatively constant for the past 4,000 years, until the relatively recent warming trend began. “You can’t find out what the climate is going to be like in 50 years for certain unless you wait 50 years,” Walker says. “But you can run a climate model ‘backwards’ to simulate what the climate was like 10,000 years ago and compare that to the paleoenvironmental data and see if there is a good correspondence between the two. If there is a greater correspondence then we have greater faith in the climate model and its ability to project into the future.” With the climate change debate growing in the mainstream media, the need for insight into the human impact on ecosystems has never been more important. Although Walker has chosen to stay at the periphery of the controversy, he acknowledges that his research was among the first to point to midges as key indicators of climatic change, prompting a slew of other researchers around the world to investigate the links between water, sediments and climate change. “When I first started, there were about two or three people elsewhere in the world working on the fossil midges and now there are dozens in most countries in Western Europe and North America,” says Walker. “I was the first person to develop a mathematical model to quantitatively confirm what past climate was like based on the midges. Coincidentally, that was just around the time that people started to become concerned about environmental change.” Although sifting lake bottoms for long-dead bugs may not prove thrilling for everyone, Walker likens his research to piecing together the fragments of a complex but critical story: “It’s like a detective story. You have these little bits of clues of what happened in the past and you try to put together a story based on those little bits and pieces.” Dr. Ian R. Walker is a Professor in the Biology & Physical Geography, and the Chemistry and Earth & Environmental Sciences units at UBC Okanagan. He has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation (CFI), the Canadian Centre for Fisheries Innovation (CCFI), Forest Renewal BC and the BC Ministry of the Environment for his projects.
November 2007
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