Johnstown Light Pollution

Johnstown’s geography is a semi-arid shortgrass prairie, marked by lively riparian corridors along its local streams. These streams all flow into the bigger South Platte floodplain system. This unique mixing of floodplain wetland and upland prairie supports a diverse array of plants and animals—yet it is an ecosystem very susceptible to the effects of light pollution.

1. Regional Ecology

According to the Guide to the Ecological Systems of Colorado, Johnstown lies within several overlapping ecoregions:

• Western Great Plains Shortgrass Prairie (199): Dominated by blue grama and buffalo grass, with scattered mid-height grasses and annual forbs.

• Western Great Plains Riparian (309): Lush streamside corridors where willows, cottonwoods, and wetland plants thrive.

• Western Great Plains Floodplain (302): Broad, seasonally flooded terraces of the South Platte River.

• Western Great Plains Closed Depression Wetland & Playa (296): Shallow seasonal wetlands that fill in low spots after rain.

• Western Great Plains Sandhill Steppe (170): Gentle sandy hills with drought-tolerant grasses and shrubs.
  
  

2. Flora

• Grasses: The shortgrass prairie is anchored by perennial species like blue grama (Bouteloua gracilis) and buffalo grass (Buchloë dactyloides), with a variety of mid-height grasses and seasonal wildflowers (forbs) that bloom after spring rains.

• Shrubs & Subshrubs: In drier areas and sandhill steppe zones, you’ll find sagebrush, rabbitbrush, and other hardy shrubs that provide nesting sites and forage.
  
  

3. Fauna

A. Historical Herds

Before European settlement, vast herds of bison and pronghorn grazed these plains, shaping plant communities and predator–prey dynamics.

B. Birds

• Grassland: Western meadowlark, horned lark, lark bunting, and grasshopper sparrow.

• Ground and Shore Birds: Killdeer, long-billed curlew, mountain plover, and burrowing owl.

• Raptors: Swainson’s hawk, ferruginous hawk, prairie falcon, and McCown’s longspur.
  
  

C. Mammals

• Canids & Mustelids: Coyote and American badger

• Lagomorphs & Rodents: Swift fox, white-tailed jackrabbit, desert cottontail, prairie dogs, and assorted mice and voles.
  
  

D. Amphibians & Reptiles

• Toads: Green toad and Couch’s spadefoot toad.

• Lizards & Snakes: Short-horned lizard, many-lined skink, coachwhip, glossy snake, massasauga, and prairie rattlesnake.
  
  

4. Migratory Birds

Johnstown lies on major spring and fall flyways. Songbirds and waterfowl navigate by starlight, and can become easily disoriented by artificial lighting. Common migrants include warblers, thrushes, and ducks, all of which depend on dark skies to reach feeding grounds safely.

5. Impacts of Light Pollution on Wildlife

1. Navigation Disruption:

   • Migratory birds rely on celestial cues. Bright, unshielded lights can cause them to circle lights until exhaustion or become easy prey.

2. Altered Behavior:

   • Studies show songbirds begin their dawn chorus earlier and delay evening calls when exposed to night lights, disrupting feeding and mating cycles.

3. Increased Collisions:

   • Disoriented birds often collide with buildings or towers near illuminated areas.

4. Predator–Prey Imbalance:

   • Raptors and owls hunting around lights may over-exploit prey drawn to the illumination, upsetting local food webs.

5. Insect Attraction:

   • Insects swarm around blue-white lights, drawing away food for bats and night-feeding birds. Red-spectrum shielding can greatly reduce this effect.

Johnstown has a Bortle scale measure of 7. The Bortle scale ranges from 0 - 9. 7 is on the higher end of the scale, corresponding to overly light-polluted big cities or transition suburban areas. The Milky Way is entirely invisible. Only the brightest constellations can be made out from the sky glow [5, 6]

There is no comprehensive ordinance in Johnstown restricting outdoor lighting. Minimal lighting guidance is provided in specific subdivision designs, such as that provided in the design for Thompson Crossing Phase II in which "Exterior and landscape lighting shall be of a conventional style with illumination patterns and intensities which do not create a nuisance for adjacent property owners"(Thompson Crossing Phase II Design ).  However, there is no overarching municipal code.