|
|
|
|
Nettle
Lake Amphibian Restoration
Conservation Plan
One of
the most important events in the evolution of vertebrates
undeniably was the movement of the amphibians from water to
a terrestrial existence roughly 360 million years ago. For
the next several million years, this group flourished with
little competition from other vertebrates, and evolved into
as
many as 15 different groups. Today, however, amphibians are
represented by only three orders: frogs and toads,
salamanders, and caecilians, a group of worm-like creatures
restricted to the
tropics. Many adaptations were required to allow the abandoning of water for an entirely
terrestrial lifestyle: limbs for support and locomotion
through a medium (air) that lacked the buoyancy of water,
moist skin and lungs for exchanging respiratory gases with
air, skin that minimized water loss through evaporation, and eggs that would not
desiccate out of water. Amphibians have
not been able to master all of these adaptations,
particularly the production of non-desiccating eggs, so most
species must still return to water (or at least a very moist
environment) to breed. Similarly, the mucous-covered skins
of most species are not very impervious to water loss, so
most amphibians are restricted to moist habitats such as
wetlands, or under leaf litter and soil, and often have
nocturnal lifestyles. Indeed, the very name amphibian
reflects the dual nature of this lifestyle - living on land
but returning to the water to breed.
Because of their relatively small size,
cryptic behavior, and mostly nocturnal habits, amphibians
are often the most overlooked of our vertebrate fauna,
especially when it comes to conservation. Historically, both
amphibians and reptiles have been feared, maligned, and
detested. These sentiments are perhaps best expressed by
Carolus Linnaeus, ironically, one of the most important
biologists of the eighteenth century: “These foul and
loathsome animals are abhorrent because of their cold body,
pale color, cartilaginous skeleton, filthy skin, fierce
aspect, calculating eye, offensive voice, squalid
habitation, and terrible venom; and so their creator has not
exerted his powers to make many of them.”
Some people today might still agree with
Linnaeus, but the fact is, there is much evidence to suggest
that amphibians play very important roles in the ecosystems
they inhabit. In some ecosystems, they are undoubtedly the
most abundant vertebrates. A study conducted at the Hubbard
Brook Experimental Forest in New Hampshire concluded that
the biomass of Redback
Salamanders was twice the biomass of
birds at peak breeding, and equal to the biomass of mice and
shrews. At the Holt Research Forest in southern Maine,
surface density estimates as high as 10,000 individuals per
hectare (approximately one per square yard) have been
documented. Densities this high suggest that this species
may play an important role in the energy and nutrient
cycling in some ecosystems. Also, amphibians are in the
middle of the trophic ladder, as predators of various
species of invertebrates, and as prey for other vertebrates.
Therefore, they might well be important in structuring the
communities that they live in.
In 1990, a group of international
herpetologists first announced the disturbing news that
populations of amphibians were experiencing unexplained,
worldwide declines, even in relatively pristine
environments. Since then, there has been little agreement on
one unified explanation, but deterioration of the ozone
layer and increased ultraviolet radiation, habitat
degradation, and acid rain have all been proposed as
culprits.
Because many species require water to
breed, amphibians may serve as biological indicators of
ecosystem health. Predation rates on eggs and juveniles are
often high, so many species have adapted a reproductive
strategy of breeding in concentrated areas. By congregating
in a few breeding sites and producing many offspring, amphibians
may saturate their predators with far more
amphibian larvae than they can eat. The
idea is that this increases the probability that at least a
few of their offspring will survive to reproduce. However,
the flip side is that this behavior makes them especially
prone to any disturbance or degradation of these
concentrated breeding sites.
Because these critters are
wetland-dependent, conservation of amphibians directly
implies conservation of wetlands. Ohio, situated in the Midwestern
agricultural belt, has lost more of its original
wetlands (90%) than all but one other state, California, and
regionally, 7 Midwestern states - Illinois, Indiana, Iowa,
Michigan, Minnesota, Ohio, and Wisconsin - are responsible
for approximately one-third of wetland losses in the United
States. Most existing federal
conservation legislation relates to amphibians only
indirectly; Ohio’s only law regarding them (1984) gives
partial protection to frogs only; an individual must possess
a hunting or fishing license to harvest or use them as bait. Many of our remaining wetlands under pressure
to be filled or drained are small in size, and variable in
time. Vernal pools are small wetlands that retain water from
spring rains and snow melt, but often desiccate completely
by late spring or summer. Many of them are important
breeding sites for amphibians, but are often not deemed
worthy of protection because of their small size or
temporary existence.
Luckily, due to increasing
education and awareness by the public, amphibians are
increasingly being considered as interesting, and worthy of
existence in their own right. Many states have begun to
research the status of their amphibian fauna, and give
funding and attention to endangered or threatened species,
and protect of critical areas, such as breeding sites. This restoration plan is aimed at
identifying and conserving critical habitat for amphibians
at Nettle Lake.
Click here to go back.
|
|
|
|
|
