The elusive tuff rock of the local creek supports endangered dragonflies

Naturalists Bob Bowles and Dieter Mueller spent Monday afternoon trudging through the woods at Historic Fort Willow looking for tuff rock in Mink Creek.

For Mueller, 75, it was an opportunity to watch the growth of tuff, a geological formation not common in this part of the world.

And for Bowles, 79, it was a chance to spot Hine’s emerald dragonfly, an extremely rare flying insect that was added to Ontario’s endangered species list in 2012.

It was thought to have disappeared but was rediscovered in 1987 at the Mink River Preserve in Door County, Wisconsin.

The species is also listed as endangered in the US and is globally endangered.

Hine’s Emerald—a medium-sized dragonfly, about six inches long, with bright green eyes, a metallic green thorax with two yellow lateral stripes, and a blackish-brown abdomen—has a habitat in Canada, and it’s at Historic Fort Willow, located about 20 minutes west of Barrie.

Bowles, a well-known local naturalist and earth science teacher, brought a net in hopes of catching one of the elusive beasts, but came up empty-handed.

One was spotted, but from a distance, and disappeared almost instantly, buzzing in the opposite direction as Bowles approached.

“Hine’s emerald is found here and nowhere else in the country,” Bowles said. “Dragonfly nymphs (larvae) need water and are deposited in tiny holes in the bush.”

According to Bowles, during a hot spell, when most of the water dries up, tuff rock will still contain moisture deep in its cracks and pores.

“This is sedimentary rock – it’s full of calcium carbonate,” he said. “It is very important because there are certain species that are calciphile; they exist in no other state.”

According to Mueller, a retired business administrator and economist with a passion for nature, geography and history, the bush grows in the Fort Willow area because of the large deposit of limestone gravel that lies underground. When it meets acidic groundwater, tuff is formed.

“The tuff deposits in Mink Creek are pretty unique,” said the Barrie resident. “They are the only place in the world where tuff is made from groundwater that has dissolved the calcium from the gravel, dust and limestone dirt.”

Mostly calcium carbonate, the same mineral that makes up limestone and marble, tuff forms through a process called precipitation or chemical deposition.

When calcium-rich groundwater travels through these porous rocks, it dissolves some of the calcium carbonate. As water rises to the surface, often as springs or seeps, it comes into contact with air, causing a chemical reaction.

Mueller says he discovered the tuff deposits three years ago while exploring the woods around Fort Willow, something he’s been doing since the early 1990s.

Recognized as both a provincial and national historic site, Fort Willow is within the Nottawasaga Valley Conservation Authority (NVCA) watershed and is generally protected from land use changes by provincial, municipal, and municipal policies and regulations. conservation.

It was used as a supply depot during the War of 1812.

The area was also actively used for centuries by First Nations, the fur trade and French explorers as part of an important transportation route known as the Nine Mile Portage.

Mueller claims that the water from Mink Creek was a huge benefit to the soldiers who were stationed at Fort Willow.

“The soldiers who came here were drinkers,” he said. “Probably a bottle of rum every day and he’d wake up with a hangover.

“I’m sure they would have taken water directly from the Mink – they would have put it in as an antacid,” added Mueller.

Although not widely known for its medicinal benefits, the water flowing through Mink Creek stimulates the growth of scrub and supports countless species of plants and animals.

In 2018, the Nature Conservancy of Canada (NCC) acquired the Patrick WE Hodgson property, a 43-hectare tract of land in the Minesing Wetlands that contains a variety of habitat types that are important to this particular dragonfly.

In 2020, NCC acquired the Baldwick Bluff property, which is connected to the Patrick WE Hodgson property. The Baldwick Bluff property serves as another 33 acres of habitat for Hine’s emerald.

The NCC, in partnership with the NVCA, has developed a restoration plan for properties that prioritize Hine’s emerald dragonfly.