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Weathering the storm

// Charlie Biddiscombe
// Charlie Biddiscombe

The days when those who dared to speak out about climate change were regarded as tinfoil-hat wearing doomsday criers are, for the most part, well behind us.

Extreme weather events that have been happening worldwide in recent years—including last year’s flooding in Calgary and High River—are a good indication of how average temperature and precipitation norms are changing.

In a recent blog post for the Pembina Institute, Dr John Stone, who has been contributing to the Intergovernmental Panel on Climate Change for many years says, “Roughly speaking, extreme temperatures have gone up by at least two degrees, which is more than twice the increase in global average temperatures. … Furthermore, the atmosphere can carry more water vapour as air temperature rises, making rains or snowfalls more intense. The result is the kind of flooding we saw in Toronto last summer. In short, climate change has loaded the dice such that the chance of an extreme event is greater.”

Extreme weather’s effect on biodiversity is an area being looked into by many scientists, and locally Ryan Fisher, a post-doctoral fellow at the University of Alberta, along with the U of A’s Dr Erin Bayne, have been co-leads on a project to understand the consequences of climate change on two grassland species: Ferruginous Hawks and Burrowing Owls.

The Biodiversity and Climate Change Adaptation Project has been monitoring Ferruginous Hawks and Fisher says it’s not just the weather that has led to a decrease in nesting pairs—about 1200 pairs remain, half the amount from 15 years ago.

“The prediction is that climate change will have a fairly significant impact on Ferruginous Hawks in the future,” Fisher says. “But it’s been speculated things like habitat loss—so conversion of native prairie to crop land and fragmentation of the grassland region in both Alberta and Saskatchewan and also in the US—may have contributed to some of the Ferruginous Hawk decline.”

Ferruginous Hawks nest in trees found on the prairies but also on artificial platforms people have set up for them. Fisher says the nests built in trees are about two times more likely than nests on artificial platforms to blow out.

“If a nest is in a tree and it falls over, the hawks are basically out of luck in terms of nesting in that particular tree,” Fisher says. “They usually try to stay within the same territory and nest somewhere else if there’s another tree available.”

But one reason for population decline is that if a nest with chicks in it gets knocked over during the summer breeding season and kills the young, the hawks won’t re-nest that year.

“That’s where these blow overs that happen in the middle of the breeding season are pretty bad for the hawks because essentially they lose out on a year of breeding and have to wait until the next summer,” Fisher notes. “Unfortunately, even though the number of nests has started to increase, the population has still been declining in Alberta and also in Saskatchewan.”

Although scientists can monitor the hawks when they arrive on the Canadian prairies, as a migratory species, it’s not known what exact environmental conditions they encounter in the fall when they migrate to the US.

“We’re still in the dark a little bit in terms of what’s happening when they leave Canada, and there definitely can be some issues related to habitat and climate change and how that affects the hawk population here in Alberta when they do come back to breed,” Fisher says.

Looking to the future, Dr Rick Schneider’s work at the U of A has shown future scenarios in the next century in Alberta ranging from 2 C to 6 C warmer. He predicts grassland will start to expand north in Alberta which will break up the parkland area and the boreal forest in the north as they both continue to recede.

“As Rick mentioned, [in his presentation] if grassland expands, that’s not necessarily a bad thing for the grassland species; it definitely has negative impacts on everything else that relies on forest and parkland,” Fisher says. “If we do see that increase in temperature and potentially increases in droughts, we’re not really sure what effect that will have not only on owls and hawks but also on their prey.

“What’s a little bit unusual and what doesn’t quite jive with those predictions is that we have actually seen a contraction in the Ferruginous Hawk range. So that just means they used to be found pretty far north in Saskatchewan up near Saskatoon and in Alberta up near Edmonton, and we’ve actually seen the hawks sort of contract south, which is the exact opposite of what you would predict in terms of climate change and changes in average temperature.”

The Burrowing Owl Monitoring Project was done in conjunction with the U of A and the Canadian Wildlife Service and lasted from about 1993 to 2010. Current estimates are between 800 to 1600 individual Burrowing Owls in Alberta and Saskatchewan—the numbers dropped by 90 percent over the ’90s. They’re a federally listed endangered species due to fairly rapid and steep population decline in the past few years.

“The goal of that project wasn’t actually to look at effects of climate, but that’s what happens when you get these nice, long-term monitoring data sets, is you can start to answer some other questions about what’s happening to these critters,” Fisher says.

Researchers doing field work noticed that when there were long periods of cold and wet temperatures, there was a lot of nest failure for the owls. Fisher got involved in the project when they started looking at what effect extreme precipitation and longer-term cold and wet conditions have on the owls.

Extreme weather on the prairies means anything around 30 mm of rain per day or more. As Burrowing Owls make their homes in holes dug by ground squirrels or coyotes, a deluge of rain tends to flood their burrows and causes all the eggs or chicks to be lost.

“What’s even more interesting is that we had a little experiment going on where we were providing supplemental food to Burrowing Owls,” Fisher says. “What was neat to see was that when we actually fed the owls and it rained, the owls were able to weather the storm. So all of the chicks in the nest seemed to be able to survive, but when we didn’t feed them, that’s when we started to see a lot of mortality of the youngest chicks in the nest. So if it’s cold and wet, the youngest chicks tend to die and it seems to be as a result of the adult owls not being able to bring enough food back to the chicks in order to sustain them during those long periods of bad weather.”

Just like with Ferruginous Hawks, once Burrowing Owls migrate south, the team has no means of monitoring them.

“Burrowing Owls go all the way down into Mexico, so what’s happening down in Mexico we really have no idea in whether or not that’s influencing current populations in Canada,” Fisher says.

The biggest factor would be habitat change in Mexico as there’s a lot of crop production in the area where the owls typically winter.

Songbirds that live in the parkland and boreal forest regions of Alberta are also at the mercy of climate change. The U of A’s Diana Stralberg has been monitoring these tiny birds with Bayne and others for the past few years.

“Here in Edmonton we’re kind of at the ecotone that transitions between the grassland and the boreal, the parkland region, so we have this very tenuous moisture balance where we’re right around a net moisture balance of zero because the precipitation is close to the evapotranspiration,” Stralberg explains. “So what’s happening in the future as it gets warmer, even if we have more rainfall, we have much higher evapotranspiration. So it’s warming and you’re kind of pushing that moisture balance into the negative, so that’s where you have the possibility for the boreal forest to shift northward. So, as that happens slowly over time, the birds shift with it. So it doesn’t mean that we don’t have birds anymore, we just have different birds. This area will be a lot more similar to something like Medicine Hat or even northern Montana.”

The problem for boreal songbirds is they’re facing both climate and land-use change.

“You’ve got all this timber harvest going on plus oil and gas extraction, so that’s knocking out forest very quickly and it’s getting rid of old forest especially,” Stralberg says. “There isn’t that much old forest left to begin with, and then climate change is also nibbling away at that.”

She says climate change and land-use change will probably work together to deplete the songbird population in Alberta as what’s currently boreal forest becomes more suitable for agriculture.

“That means a lot less room for shifting of biodiversity,” Stralberg says. “Obviously a lot has been lost, but a lot is still left. So I think it’s just a matter of allowing ourselves to shift that baseline and not be so focused on what’s here now, but trying to think about how it may look in the future.”

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