Cliffs and Their Unique
Ecosystems
A cliff is a steep, often
vertical face of rock, earth, or ice, commonly formed by erosion, weathering,
and the force of gravity. Unlike hills, which slope gently, cliffs rise
sharply, sometimes appearing almost perpendicular to the ground.
Among the most iconic examples are the
White Cliffs of Dover, formed nearly 500 years ago by Ice Age floods. Their
striking white colour makes them visible even from the French coast on clear
days. I had the opportunity to visit them during my last tour of England—a
truly unforgettable sight.
Geographically, cliffs occur in
coastal areas, mountain ranges, riverbanks, and escarpments. Despite their
harsh terrain, these vertical landscapes support surprisingly rich ecosystems.
Cliffs feature ledges, cracks, and crevices that offer microhabitats to a
variety of plant and animal species. These environments, though challenging to
study due to their vertical nature, are biologically significant and often
overlooked.
The Niagara Cliffs: A Hidden Wilderness
One of the most fascinating cliff
systems extends from the Niagara Falls area, tracing a line through the Great
Lakes region to Door County, Wisconsin, and disappearing beneath glacial till
near Chicago. This region, known as the Niagara Escarpment, consists largely of
dolomite rock and has undergone centuries of natural erosion. Notably, a
dramatic collapse occurred at Niagara Falls in the 1850s, sending a horse-drawn
carriage tumbling into the canyon—a stark reminder of the cliffs' dynamic
nature.
Before 1986, the limestone cliffs
along this escarpment were thought to be barren. However, naturalists and
climbers later discovered stunted forests, ferns, lichens, and signs of
wildlife, including bobcats, chipmunks, and snakes, inhabiting the cliff face.
This sparked a deeper question: How do trees grow from bare rock?
This simple inquiry led to revelations
about an ecosystem containing some of the oldest and slowest-growing trees in
Canada, as well as ancient woody debris unmatched in any eastern North American
forest.
Cliffs as Distinct Ecosystems
To determine whether cliff habitats
are distinct from surrounding forests, scientists examined whether the cliff
ecosystem changes in tandem with adjacent landscapes. They found that it does not
confirm the cliff as a unique ecological zone.
Sixty-six feet from a cliff edge, the
forest reflects regional norms: tall canopies, diverse flora, rich soil, and
moderate environmental conditions. As one approaches the edge, the soil thins
and the canopy shortens, though tree species remain similar. Within two meters
of the edge, conditions change drastically—soil becomes sparse, water
availability fluctuates, and protection from snow vanishes. Here, plants such
as dogwood, ferns, and grasses adapted to dry, harsh environments dominate. The
cliff-edge trees—primarily Thuja occidentalis (eastern white cedar) and Juniperus
virginiana (eastern red cedar)—show twisted, deformed growth where they
emerge from the rock.
Life on the Cliff Face and Beyond
From the cliff edge to the base,
gravity dictates ecological structure. Organisms here endure crumbling rock,
extreme temperatures, and scarce resources. Algae, fungi, and lichens inhabit
rock crevices, while resilient trees and ferns cling tenaciously to the cliff
face. Birds of prey use the inaccessible ledges for nesting.
At the bottom, fallen debris and
enriched soil form a chaotic landscape of lush vegetation—dogwood, impatiens,
raspberries, and even poison ivy—amid bare rocks and shattered limbs. Snakes
are common, thriving in this rugged terrain. As the slope becomes more gradual,
the ecosystem again mirrors the rich forest found atop the plateau.
How Do Cliffs Host Such Life?
At first glance, it seems cliff
species are specially adapted to these environments. However, experiments
revealed a surprising truth: the cliff is inhospitable to all species,
including those dominating it. Eastern white cedars, though prevalent on cliff
faces, grow poorly there and thrive in nearby forests. When seedlings are
planted on cliff edges, they die within a season—but survive for years in
adjacent woodlands.