'The Hine's emerald is found here and nowhere else in the country,' local naturalist says of stream running through Historic Fort Willow
Naturalists Bob Bowles andDieter Mueller recently spent an afternoon trudging through the forest at Historic Fort Willow looking for tufa rock inMink Creek.
For Mueller, 75, it was an opportunity to track the growth of tufa, a geological formation that is not common in this part of the world.
And for Bowles, 79, it was a chance to spot the Hine’s emerald dragonfly, an extremely rare flying insect that was added to Ontario’slist of species at riskin 2012.
It was thought to be extinctbut was rediscovered in 1987 at the Nature Conservancy’s Mink River Preserve in Door County, Wis.
The species is also listed as endangered in the United States and is globally imperilled.
The Hine’s emerald—a medium-sized dragonflyabout sixcentimetres long, with bright green eyes, a metallic green thorax with two lateral yellow stripes, and a blackish-brown abdomen—has one habitat in Canada, and that is atHistoric Fort Willow, located about 50 kilometres southwest of Orillia.
Bowles, a well-known Orillia naturalist and Earth sciences teacher, brought along a net in hopes of catching one of the elusive beasts, but he left empty handed.
One was spotted, but from a distance, and it disappeared almost instantly, buzzing off in the opposite direction asBowlesapproached.
“The Hine’s emerald is found here and nowhere else in the country,” Bowlessaid. “The dragonfly nymphs (larvae) need water and they’re deposited in the tiny holes in the tufa.”
According to Bowles, during a heat spell, when most of the water dries up, the tufa rock will still contain some moisture deep in its crevices and pores.
“This is sedimentary rock—it’s full of calcium carbonate,” he said. “It’s very important because there are certain species that are calciphiles;they don’t exist in any other condition.”
According to Mueller, a retired business administrator and economist with a passion for nature, geography and history, tufa grows in the Fort Willow area due to the large deposit of limestone gravel that’s below ground. When it meets acidic groundwater, tufa forms.
“The tufa rock deposits in the Mink Creek are quite unique,” said the Barrie resident. “They are the only place in the world where tufa is made from groundwater that has dissolved calcium from limestone gravel, dust and dirt.”
Mostly calcium carbonate, the same mineral that makes up limestone and marble, tufa 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 the water emerges to the surface, often in the form of springs or seeps, it comes into contact with the air, causing a chemical reaction.
Mueller says he discovered the tufa deposits three years ago when he was exploring the forests around Fort Willow, something he’s been doing since the early 1990s.
Recognized as both a provincial and national historic site, Fort Willow sits within the Nottawasaga Valley Conservation Authoritywatershed and is generally protected from land-use changes through provincial, municipal and conservation authority planning policies and regulations.
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 a major transportation route known as the Nine Mile Portage.
Mueller theorizes 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 — likely a bottle of rum every day and they’d wake up hung over,” he said.
“I’m sure they would have taken water straight from the Mink.Itwould have settled them down like an antacid.”
While not widely known for its medicinal benefits, the water that flows through Mink Creekpowers the development of tufa and supports the existence of untold numbers of plant and animal species.
In 2018, the Nature Conservancy of Canada acquired the Patrick W.E. Hodgson property, a 43-hectare piece of land in the Minesing Wetlands that contains a variety of habitat types that are important for this particulardragonfly.
In 2020, the Nature Conservancy of Canada acquired the Baldwick Bluff property, which is connected to the Patrick W.E. Hodgson property. The Baldwick Bluff property serves as another 33 hectares of habitat for the Hine’s emerald dragonfly.
The Nature Conservancy of Canada, in partnership with the Nottawasaga Valley Conservation Authority, has developed a restoration plan for the properties that have the Hine’s emerald dragonfly as a priority.
