City at tip of southern and northern range for several species
Outsiders may associate Hamilton with steel mills and smokestacks, but a new study suggests the city deserves to be known for something else: an abundance of nature.
Conducted over the past three years, the natural areas inventory surveyed more than 5,400 hectares of land and water, tallying 1,144 different plant, insect and animal species, including 23 new ones and 150 considered endangered, threatened or of special concern.
The findings arguably make Hamilton one of the best areas for biodiversity in Canada, said Nicholas Schwetz, coordinator of the survey, a joint project of the Hamilton Conservation Authority, City of Hamilton and Hamilton Naturalists’ Club.
The abundance not only gives people lots of interesting things to look at, but makes the city’s natural areas more resilient to changes and external pressures than those with lower biodiversity, he said.
“There’s more niches and habitat types and interactions,” Schwetz said following a presentation on the survey to conservation authority directors. “The more biodiversity you have in an area, ecologically speaking, the healthier it can be.”
Among the survey’s surprising new finds is that the pawpaw tree — more common to the shores of Lake Erie and known for an edible yellow-green fruit that looks a bit like a mango — has made its way to Hamilton.
Bald eagles, sandhill cranes and the common raven, which usually prefers more northern climes, were also new to Hamilton, as were three butterflies — the American snout, cherry gall azure and grapevine epimenis moth.
Building on previous surveys completed in 1993 and 2003, the latest study for the first time counted dragonflies and damselflies, recording 16 kinds, many of them classified as rare and a good indicator of ecosystem health for wetlands, Schwetz said.
Hamilton’s location in a Carolinian forest zone with distinctive features like the escarpment, lake and bogs help make it unique, he said.
The city has 90 different species of trees, more than four times the number found in Canada’s boreal forests.
“Many species of plants and animals are either at the northern range of southern species or at the very southern range of northern species,” Schwetz said. “It contributes to a very complex matrix of ecosystems and habitats.”
Not all the news is good, though. The survey counted 65 exotic invasive species and six reptiles and amphibians that were previously common to Hamilton were rarely spotted, including the smooth green snake.
Reflecting a wider trend of declining monarch butterfly populations, only four areas had an abundance of the milkweed that their larvae feed on, compared to 109 where they were more scattered.
Schwetz said the results of the $700,000 survey will be compiled in a report with specific site recommendations, expected to be published by early next month.
The data will be shared with a variety of local and provincial agencies, helping to guide the conservation authority’s stewardship programs and city land-use policies, he said.
Authority chair Brian McHattie said the database is a rarity in Canada and he hopes it will be used to help track trends on species loss and gains, like the appearance of the pawpaw tree, which may reflect climate change.
“One of my concerns is we’re not fully utilizing the power of that database, not only for our own purpose,” he said, suggesting university graduate theses could study the reasons for changes in species counts.
Schwetz said the survey does allow for a sense of trends, but its completeness is affected by lack of access to some private lands.
It also didn’t include any small mammal trapping this time around, so it didn’t assess how bat populations are being affected by the white-nose syndrome that is decimating them elsewhere, he said.
“We are able to track certain changes but not as in-depth as what we could with more research going forward,” Schwetz said, suggesting 10 years between studies is too long, especially since not all the same areas are surveyed.