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Allison Sacerdote, Reintroduction Biologist, Lincoln Park Zoo
March 24, 2012

Allison Sacerdote began her power point presentation by informing the group that amphibians are the most endangered group of species (taxon) in the world. In the past 20 years, 168 species have been lost to contaminants and pollution. 32% of amphibian species are currently threatened with extinction. 43% of species are in decline. Amphibians are vulnerable to contaminants because of their permeable skin.

Frogs represent the world's largest biomass (net weight of organisms). Amphibians (frogs and salamanders) represent a large proportion of the world's biomass (e.g. in the northeast U.S., redback salamanders represent 2-4x the biomass of small mammals).

In some areas of the world, frogs are hunted for food and are also used as medicinal remedies, aphrodisiacs, drug abuse or for the pet trade. Habitat loss through destruction or fragmentation, disease, ultra violet radiation, invasive species and climate change are known contributors to species extinctions and population declines. In Illinois, 85% of our pre-European settlement wetlands have been drained, plowed or filled, destroying habitat for amphibian survival and breeding.

Chorus frog Pseudacris triseriata

One of the most serious diseases facing amphibians today is Chytridiomycosis. 370 frog species on all continents are infected with this fungal disease. The disease is usually fatal. When frogs contract the fungus, rapid death follows and entire populations can be lost. Metamorphs are the most vulnerable life stage. Populations in high elevation streams appear especially susceptible to fungal infection. Some of the hardest hit areas impacting amphibian survival are the tropics, sub-tropics and high elevation ecosystems.

Pesticides, herbicides and birth control pills in wastewater suppress amphibian immunity and contribute to malformations in frog limbs and reproductive organs, with amphibians often experiencing increased trematode loads.

Many frogs and salamanders breed in vernal ponds in the U.S. Mosquito larva hatching in ponds is the favored salamander larva food. Without amphibians to control mosquito numbers, diseases like malaria carried by this insect, may impact the health of birds, animals and humans. Tadpoles are important algal grazers, controlling algal and nutrient dynamics in many aquatic systems. Without tadpoles grazing, aquatic systems experience a loss of macroinvertebrate diversity and abundance.

Tadpoles serve a very important role in ecosystem sustainability. As they mature, they carry nutrients from the water to the land Amphibians also provide a source of food for herons, small mammals and snakes. Without this predator/prey interaction, a vital link in nature's cycle is severed and biodiversity on earth declines.

Climate change is altering the length of time ponds hold water and reduces the time tadpoles have to develop sufficiently to leave the water for land. Increased drought, longer growing seasons, increased herbicide and pesticide use also reduce amphibian survival rates.

Bull frog Rana catesbeiana

Road mortality is also responsible for amphibian deaths when highways divide amphibian habitats. Frogs attempting to make the crossing are frequent casualties on the road. To prevent these deaths, Critter Crossings and signs are posted to alert drivers. Frog underpasses and fences are being installed and thousands of frogs are being saved each year as a result.

Buckthorn, the scourge of Illinois woodlands and prairies, is another threat to amphibians. Buckthorn litter breaks down quicker and alters the fertility of the soil. Water uptake by buckthorn sprouts along pond margins may further limit the amount of time a pond holds water, which can affect amphibian recruitment. Decreases in leaf litter in buckthorn stands may limit amphibian movement between ponds and upland habitats. A metabolite produced by buckthorn may suppress amphibian hatching success. (Because this paper on buckthorn impacts on amphibians by Allison Sacerdote is still in review, we cannot make an outright statement at this time about the ecotoxicity issue. But once it is reviewed and accepted for publication, we can discuss this further).

Here are some solutions underway to reverse amphibian extinctions and population declines:
--In southeastern Iowa, 470,000 acres have been set aside as an Amphibian and Reptile Conservation Area.
--Threatened frog species are collected and transferred to Frog Pods or mobile laboratories for captive husbandry and breeding.
--Agricultural tiles are removed to restore hydrology and create amphibian habitat on degraded sites.
--Native plants are returned and invasive plants are removed. Prescribed burns are introduced.
--Filled areas are excavated to create vernal ponds and wetlands.
--Private landowners are encouraged to preserve wetlands through the Wetland Reserve Program.
--Threatened and endangered amphibians are bred in zoos and aquariums to save them from extinction.
--Researchers collaborate around the world in search of solutions to control or cure diseases and recommend ways to reverse habitat loss in order to return captive bred species to their natural environments in the future.
--The Nature Conservancy, Amphibian Arc, Chicago Wilderness and PARC are just a few organizations working on amphibian conservation.

Amphibians are the flagship indicator species forecasting the stability or decline of biodiversity on Earth. Saving amphibians and restoring amphibian habitat benefits a whole suite of species locally and globally.

Amphibian photos by Mike Redmer, Nature and Natural History Photography and Writing
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