What these 58 Ontario lakes can teach us about climate change

TVO.org talks with Scott Higgins, a scientist with the Experimental Lakes Area, about data collection and what a half-century of research reveals about climate change
By Jon Thompson - Published on Sep 16, 2019
Scott Higgins has been a research scientist with the Experimental Lakes Area, in northwestern Ontario, since 2010. (International Institute for Sustainable Development)

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Along the remote corridor between Kenora and Dryden, there are 58 small lakes set aside exclusively for scientific research. Called the Experimental Lakes Area — and, since 2014, managed by the International Institute for Sustainable Development — the region has been the subject of scientific examination since 1968. The IISD calls the lakes “the world’s freshwater laboratory” and “one of the only places” on Earth where researchers can conduct experiments on entire ecosystems. Scientists introduce species and other variables to the waters and study everything from algal blooms to mercury poisoning to oil spills.

The program serves as an invaluable resource for scientists studying climate change. Using a half-century of rigorous data, IISD researchers have found that the higher temperatures and increased precipitation associated with climate change are affecting northern Ontario’s lakes and watersheds.

TVO.org spoke with Scott Higgins, a research scientist with the Experimental Lakes Area, where he’s worked since 2010, about data collection methods, the lake trout’s tough choice, and why lakes can be both carbon sinks and carbon emitters.

How does the ELA ensure that the data it collects is accurate and useful?

Whenever you do an experiment in a lab — or, in our case, in the natural environment — you need references or controls. So they set aside a number of lakes to be “reference lakes,” where no manipulations were done.

When we’re understanding the impacts of climate, what we’re doing is using five lakes that haven’t been manipulated but that we’ve monitored very intensively. They weren’t designed to monitor climate change, but, over 50 years, the data we’ve created and the intensity of that data have made those data sets incredibly useful.

We have an onsite meteorological station, which we’ve operated with Environment Canada since 1969, where we get all the standard meteorological data, and it’s within the watershed of one of our lakes, so it’s less than a kilometre away from our reference lakes. There, we get air temperatures, rainfall, barometric pressure, solar radiance, wind speeds, and the nutrients that are in the rain.

You point out that, in the region more broadly, air temperature is rising five times faster than the global average. How has that affected the ELA?

The surprising thing to me and to many when we look at the data is when you hear air temperatures are increasing, we make the unconscious assumption that it’s evenly distributed across the seasons. What the data says is that the winter’s warming much, much faster than the summer is. In our data, the summer isn’t even significantly increasing.

I suspect that, over time, the summers will become significantly warmer, but the big changes are occurring in the winter and the shoulder seasons. December, for example, was increasing by over a degree per decade — so, much faster than the mean trends.

Right now, it affects the phenology of the ice. When the ice forms in the fall and when it melts in the spring, those dates are significantly changing. The period of ice cover is shortening dramatically.

ELA research shows that average annual precipitation has increased by 19.1 millimetres per decade since 1970. What impact has that had?

The big story is that we’re seeing more dissolved organic carbon coming off the watersheds in the wetlands and moving into these lakes. Dissolved organic carbon stains the water a tea colour from the acids that are associated with wetlands and these soils.

As more DOC comes into the lake, you lose transparency. That’s when you step into a lake and you can’t see your feet after the first foot or two in the water. That affects things that depend on light to grow,  like plants, and those are the base of the food web.

We’ve looked at the whole range of lakes in the region — the clear lakes and the really dark lakes — and asked how it affected the physical properties and the chemical properties. In our darkest lakes, plants can only grow in the top four to five metres, but, in our clearest lakes, they can grow down to 20 metres or more, so you lose three-quarters of your habitat in that range.

We have a study that’s just wrapping up right now. Essentially, what they’re finding is that the changes in dissolved organic matter have a strong impact over primary production, which is plant growth: the base of the food web.

Climate change is making our watersheds more sensitive to land use, so, as we move into the future, we’re really going to have to think about how we manage and use these watersheds appropriately, because it can lead to these very costly issues around algae blooms. The City of Winnipeg is talking about spending upwards of $1.4 billion on upgrading its north-end sewage-treatment plant. The main purpose is to reduce these algal blooms in lake Winnipeg.

You’ve noticed that lake trout are shrinking in size as their habitat changes. Can you explain why that’s happening?

We think it’s related not to the changes in surface-water temperatures, because, remember, our summer air temperatures haven’t changed very much. But what has changed is that the summer period has gotten longer — what we call the “summer starvation period” for lake trout.

Lake trout feed intensively in the spring and fall when water temperatures are mesothermal — they’re the same from top to bottom because it’s mixing. As the summer gets longer, that summer starvation period gets longer. Then the thermocline [the water temperature gradient] starts to deepen over time, and this anoxic zone [an area uninhabitable because of low oxygen levels] at the bottom of these lakes creeps up. Habitat becomes unavailable for lake trout. And, if the summer gets longer and longer, the higher temperature and the lower oxygen will overlap, so there will be no optimum habitat for lake trout.

What lake trout have to do is decide, “Am I going to live in a sub-optimal oxygen habitat, or am I going to live in a sub-optimal temperature habitat?” No matter what they choose, there’s an impact on their metabolism, and growth rates will slow. We believe we’re seeing the first indications of that in the lake trout data. They’re getting shorter in length and skinnier in size.  

The ELA is in the southern section of the Boreal Shield Ecozone, which stretches from Saskatchewan to Newfoundland. What do your findings tell us about the ecozone as a whole?

Boreal lakes are both carbon sinks and carbon emitters. It’s the biggest ecozone on the planet, so it plays an important role in the global carbon balance. We talked about how increases in rainfall push dissolved organic carbon from wetlands into the lake. Once that carbon goes into the lake, some of that carbon sinks to the bottom and becomes permanently buried in the sediments. That’s how lakes are carbon sinks. But a portion of that carbon gets worked over by bacteria and respired up to the atmosphere, so that carbon dioxide is a greenhouse gas that contributes to global warming in a positive feedback loop. More rainfall means more carbon-dioxide emissions from lakes, even though lakes are net carbon sinks.

As Canada moves forward to reduce its carbon emissions to do its part in reducing climate change, what happens in the boreal zone is also really important because it could dwarf all those efforts. We need to be able to model how carbon fluxes in the boreal forest. That’s important to every Canadian and everyone around the planet, I think.

This is one in a series of stories about issues affecting northwestern Ontario. It's brought to you in partnership with Confederation College of Applied Arts and Technology. Views and opinions expressed in this article are not necessarily those of the college.

Ontario Hubs are made possible by the Barry and Laurie Green Family Charitable Trust & Goldie Feldman.

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