Adapting to Yukon’s changing climate: polargrass gains, hairy braya loses out

In the northern reaches of the Arctic, where the Beaufort Sea licks the sandy outcrop of land on Cape Bathurst peninsula in N.W.T., there’s a small population of flowering plants that can’t be found anywhere else in the world.

By Vivian Belik

In the northern reaches of the Arctic, where the Beaufort Sea licks the sandy outcrop of land on Cape Bathurst peninsula in N.W.T., there’s a small population of flowering plants that can’t be found anywhere else in the world. The hairy braya, a white-flowered, fragrant mustard, is not only extremely rare – it’s on the verge of extinction, a situation that is worsening because of climate change.

When Scottish explorer Sir John Richardson discovered Cape Bathurst peninsula in 1826, the bay he pulled into was likely crowded with hairy braya. He described the flowers as fragrant, with a smell similar to lilac blooms. When botanist Jim Harris retraced Richardson’s footsteps in 2004, he found that the population of this endemic plant had decreased significantly.

Seven years later, when Yukon researcher Bruce Bennett returned with Harris to the same spot, he found that the number of plants had shrunk further, from several thousand to several hundred. “It was a tenth of what Jim Harris had seen just a few years before, and it’s likely that if you were to go to that spot now, the entire population would be gone,” Bennett says.

The hairy braya relies on insects to reproduce, doesn’t compete well with other plants, and is killed by overwash of salt water. But the biggest factor affecting the plants’ survival is eroding shorelines caused by increased wave action due to the reduced sea ice in the Beaufort Sea. This situation will only worsen as sea levels continue to rise as a result of climate change.

The plants are often found about 50 metres from shore and shorelines are eroding at a rate of 10 metres per year, says Bennett, the coordinator of the Yukon Conservation Data Centre. “There seems to be enough evidence that the trajectory is not very good for this species, and it may be one of the first species we see go extinct in the North as a result of the effects of climate change.”

Since 2005 Bennett has been a member of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), and three years ago became a co-chair of the organization’s vascular plant subcommittee. He’s been paying close attention to which plants and animals in Yukon may be heading down the same path as a result of increasing storms, changing sea levels, loss of sea ice, increasing temperatures, and unpredictable weather.

As on the Cape Bathurst peninsula, there are sandy dunes along the Yukon coast that host plants and invertebrates that are starting to disappear as the dunes erode and fall into the ocean. “The shoreline is eroding too fast for species to move or adapt. If you were a species on that dune and you lived on the coast, your habitat is gone,” says Bennett. “This may be the case for many invertebrates and plants.”

Some inland species may be at risk too. The collared pika, a rodent that looks like a hamster but is more closely related to a rabbit, is a Beringian species that lives in alpine areas in the Yukon. The animal has a limited ability to thermoregulate, or control its own body temperature, and spends the hot summer hiding in cool rocky crevices.

But these rocky areas are at risk of heating up. Bennett points to the collared pika’s relative, the American pika, which is experiencing rapidly increasing rates of local extinctions and dramatic range shifts as a result of the increasing pace of environmental change. Found in the southern Rocky Mountains and the Great Basin, American pikas are moving higher up into the mountains, and their numbers are shrinking in the southern range because it’s too hot and dry. “We may see the same thing in the Yukon. Pikas are a bit of a canary in the coal mine,” says Bennett.

The Yukon draba is a small plant found between Haines Junction and the Aishihik, mostly in low-lying grasslands. But many of these drier grasslands are becoming shrubbier and infilling with species like aspen. The territory’s wetter and warmer springs and summers could be the cause. But it might also be an increase in carbon dioxide in the atmosphere, says Bennett, which allows the plants to grow faster.

Although the Yukon has already started to see some effects of climate change, the territory is somewhat sheltered as compared to other areas. The numerous mountainous regions create different micro-climates that allow for more biological diversity. It’s this diversity that is adding a “buffer” to the effects of climate change. It’s only a matter of time, however, before the territory starts noticing significant changes, says Bennett, particularly in coastal areas, which are more vulnerable.

One way to make the territory’s native plants and animals more resilient is to prevent the introduction of invasive species. “Most of our invasive species have been introduced intentionally,” says Bennett. “We do it by building roadways, through agriculture and horticulture.” Compared to other areas in North America, the Yukon has a big advantage because it has fewer such species. “The absence of an invasive species may allow some of our native species to adapt, but if these invasive species increase, we lose that one little advantage,” says Bennett.

It’s a guessing game as to which plants and animals will be able to adapt. Some species will be better suited to climate change than others. Some may even benefit, such as the grey whale, which has been sighted in Yukon waters since the 1980s. Having a thinner ice pack on the Beaufort Sea may be an advantage to the whale, says Bennett. Certain species of gulls and polargrass are also becoming more abundant as a result of climate change.

Specific research into which components of climate change are affecting species’ habitat is key. Groups like the Yukon Conservation Data Centre relay studies and information about species at risk to COSEWIC, which recently came out with new guidelines on how to evaluate effects of climate change and include them in threat calculators. Just saying a plant or animal is affected by climate change is no longer enough, says Bennett. “You have to be able to say what aspects of climate change are a threat.”

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at http://www.yukoncollege.yk.ca/research/publications/newsletters_articles.

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