“Edge effects are the changes in biodiversity that occur inside the space surrounding the shared edge of two or more distinct ecosystems. This transitional zone rich in biodiversity is known as the ecotone; examples are between woodlands and plains, forests and mountains, and land and water.”
~ Gia Mora
I live in a small town that abuts the Denver Metropolitan area just to the east of our two mesas and therefore has many of the attributes of a city, yet keeps the small-town ambience. On the western edge of the town, the Front Range of the Rocky Mountains shoots up nearly two thousand feet, keeping the undeveloped, wild aspect of Colorado right next door.
We live on the edge of two very different system, and we both benefit and suffer from each. Writer Gia Mora explains, “When two adjacent habitats have enough individual space to allow for an ample gradient edge, the ecotone is uniquely positioned to provide habitable conditions for certain plants and animals. Thriving edges house the greatest variety of natural structures, ranging from small to tall, and they often boast wildlife populations exceeding any bordering habitats.”
The blend of systems can be very productive, as well as very challenging. With a short drive or long walk we can access metro-area malls, stores, restaurants and other city attractions. We do have handy access to excellent medical facilities and other services, as well as a short drive for the sort of employment opportunities available in a metro area. We have ready access to government at the local, state and national level.
We suffer some of the traffic problems of the city, and sometimes the wind traps the city smog up against our foothills. The edge of the mountains provides a handy avenue for bird migration north and south, and different seasons drive various wildlife up from the plains or down from the hills.
With a short, steep hike or drive we can be among the pine trees with exotic mountain vistas. In addition to highways and boulevards, we enjoy bus and light rail service, but have to keep an eye out for the elk, deer, and sometimes, bear or moose that venture down from the hills. Our local river is wild enough to kayak, but tame enough for tubing.
Mora continues, “Inherent edges are naturally occurring changes that are generally considered wide; they provide adequate space for species in and outside the ecotone to prosper … Unlike the interiors of most ecosystems, edges receive more sunlight, experience less humidity, face more wind, and experience higher temperatures. These environmental differences enable a more hospitable environment for high light, drought-tolerant flora. Consequently, more herbivorous insects, birds, and other animals can make their homes inside the ecotone.”
“Urbanization, lumber harvesting, and food cultivation all result in induced edges … Once these negative edge effects take hold, the climate along the edge can spread deeper into the environment, threatening habitat destruction for a number of species that can only survive in the original biomes.”
The impacts of the edge can be addressed by allowing diverse uses. My town has avoided extreme sprawl because of natural conditions: our borders are created by the mesas and the Front Range. That has prevented us from becoming a blur of urban sprawl like the suburbs to our east out on the plains. However, many of those areas also provide lots of mixed uses: parks, open space, agriculture, and large lots cultivated with trees and other vegetation. Also yet, streams coming out of the mountains have been mostly preserved in a natural state providing corridors for wildlife.
An old town dating back to the mid-1800’s, my neighborhood is full of established shrubs and lawns and big, old trees. There are many wild species that adapt to these suburban ecosystems, including raccoons, squirrels, rabbits, coyotes, and deer. Maintaining, or not destroying, natural and vegetated areas helps these animals survive.
Many bird species also thrive in the suburban areas. In addition to several bird feeders, I have preserved the native chokecherry bushes that thrived around my lot, and they are immensely popular with various bird species, both for food and habitat.
Frequently, when I check the feeders in the backyard, I find a feather on the ground below. I like to think of this as a thank you gift from the birds for providing food, habitat and a sense of belonging in my yard.
I keep and treasure each feather.
Gia Mora, Edge Effects: Habitat Biodiversity and Human Interference, August 9, 2022, TreeHugger