Amphibians glands, indicate an ecosystem’s health, and consume

            Amphibians
are a valuable part of the global ecosystem; they contribute medicine with
their poison glands, indicate an ecosystem’s health, and consume detrimental
pests (Zippel, n.d.). However, out of the 5743 known amphibian species, 1856
(32.5%) are globally threatened (Stuart et al., 2004) and the current global
amphibian extinction rate ranges from roughly 25,000 to 45,000 times more than
historical rates (McCallum, 2007). In Yellowstone National Park, McMenanin, Hadly
and Wright (2008) observed that from 1992 to 1993, 43 (93%) of the 46 active
ponds surveyed had an amphibian population, which decreased to 21 (68%) of the
31 active ponds from 2006 to 2007. Around New South Wales,
Australia, researchers found Pseudophryne
pengilleyi was absent, from 2007 to
2010, at 19 (42%) of the 45 local sites that had supported the species from
1997 to 2006 (Scheele, Driscoll, Fischer, & Hunter, 2012). Other studies
found similar declines in Europe; of all 84 native amphibian species, 59% have
declining populations and 25% are considered threatened (Temple & Cox,
2009). Locally, in the Blue Ridge Escarpment of North Carolina, researchers
noticed a 98% decrease in the relative abundance of Aneides aeneus from 1970 to
the 1990s (Corser, 2001). Additionally, a study found that the Ambystoma maculatum egg mass count
decreased by 23.9% from 1988 to 1991 in vernal pools around Richmond, Virginia
(Blem & Blem, 1991).

Researchers have found several factors that
contribute to this global decline. Habitat loss is a major problem for both
global and local amphibian populations. Most amphibians use forested land as a
habitat and in Virginia, urbanization has caused the loss of over 500,000 acres
of forested land since 1977 (Sevin & Kloepfer, 2015). In Southeast Asia, if
urbanization continued at its present-day rate 75% of all originally forested
land will disappear by the year 2100,
creating an estimated 42% decrease in biodiversity (Rowley et al., 2010).
Amphibians are also particularly sensitive to anthropogenic pollutants and acidification
due to the permeability of their skin (Quaranta, Bellantuono, Cassano, &
Lippe, 2009; Blaustein & Wake, 1990). In Australia, researchers noticed
that the fungal disease chytridiomycosis contributed to the decline of 43 (18%)
of all 238 native amphibian species and that population stability was mostly
due to certain environmental factors that restricted the disease’s effect
(Scheele et al., 2017). Climate change and higher temperatures also contribute
to amphibian decline; in Yellowstone National Park, declining amphibian
populations correlated with a 4-fold increase in permanently dry pools from
1992 to 2008, a result of decreasing precipitation (McMenanin et al., 2008). In
addition, researchers have observed that the dissolved oxygen concentration of
an amphibian’s habitat is critical to its survival, especially as an embryo
(Seymour, 1995).

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