The natural night — true darkness, undiluted by the amber glow of cities and roads and parking lots — is becoming one of the rarest environments in Canada. From above, the country's most populated southern corridor is a near-continuous wash of light. Even areas that appear to be rural in daylight are bathed in a diffuse artificial luminescence that fades only at distances of hundreds of kilometres from any settlement. The part of Canada that still experiences genuine natural darkness is its north — and even there, the reach of light pollution is extending.
This matters for reasons that extend far beyond astronomy, though the loss of the night sky is itself a significant cultural and aesthetic impoverishment. Light pollution is an ecological stressor of the first order, affecting the behaviour, physiology and survival of a vast range of species that evolved in a world where darkness was a reliable feature of every twenty-four hour cycle. The nocturnal ecology of Canada — the foxes, wolves and lynx that hunt after dark, the owls that navigate by starlight, the bats that detect insects through echolocation, the insects and frogs whose breeding calls are the soundtrack of warm summer nights — is under pressure from a threat that receives a fraction of the attention given to habitat loss and climate change, despite being similarly pervasive.
The Acoustic Dimension of Night
Night is, acoustically, a different world from day. Many of the animals most active after dark communicate through sound rather than vision — because in darkness, sound carries information that light cannot. The repertoire of nighttime sounds in a healthy Canadian ecosystem is distinct from the dawn chorus: owls calling across territories, the peeping of spring peepers in March wetlands, the tremolo of a common loon carrying across a boreal lake, the clicking of bats echolocating over a still pond. These are among the most evocative sounds in the Canadian natural environment, and they are tied to particular times, places and ecological conditions that are changing.
Nightjars — the whip-poor-will and the common nighthawk — are among the most distinctive nocturnal soundmakers in Canadian forests and open country, and both have experienced significant population declines. The whip-poor-will's call, once a reliable soundtrack of late spring evenings across much of eastern Canada, has become rare enough in populated areas that many younger Canadians have never heard it. The causes of decline include habitat loss, declining insect prey biomass and light pollution that disrupts the crepuscular timing of these aerial insectivores.
What Bats Tell Us
Bats are the most diverse group of nocturnal mammals in Canada, with nineteen species occupying habitats from coast to coast. They are also one of the most ecologically important: insectivorous bats consume vast quantities of agricultural pests and mosquitoes, providing ecosystem services worth billions of dollars annually to Canadian farming. The catastrophic decline of several bat species due to white-nose syndrome — a fungal disease that kills bats during hibernation — has reduced populations by more than 90 per cent in affected areas in eastern Canada, with ripple effects on both ecosystems and agriculture that are still being assessed.
Dark Sky Preserves and the Fight for the Night
Canada has more designated Dark Sky Preserves than any other country — parks and protected areas where artificial light is controlled to preserve natural darkness for astronomy, ecology and simple aesthetic experience. The Royal Astronomical Society of Canada has driven this programme, and Parks Canada has incorporated dark sky considerations into management planning for a growing number of parks. The economic case for dark sky preservation is increasingly being made alongside the ecological one: dark sky tourism, centred on the experience of the Milky Way and aurora borealis, is a growing sector that gives communities adjacent to dark sky preserves a direct financial stake in limiting light pollution.