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Science & NatureGreen TalkAmphibians and their role in the web of life

Amphibians and their role in the web of life

Amphibians and their role in the web of life – what if they disappeared?

by Theresa Peluso

Frogs, toads and salamanders. How many of us, as children, caught tadpoles in the local pond and then tried to nurture them into adulthood in a jar on our bedroom dresser, with only the occasional success? Or caught a glimpse of a salamander near the edge of a lake or under a rock? The enthusiasm for amphibians continues, one example of which is the hugely popular Mudpuppy Night in nearby Oxford Mills, where every Friday evening, from Thanksgiving until spring high-water, people can view these giant aquatic salamanders going about their normal activities.

Mudpuppy (Necturus maculosus)

Although the total biomass of amphibians is negligible compared with the total biomass of all animals on our planet, they nevertheless play a critical role in our ecosystem. The AmphibiaWeb database (as of Aug. 2018) currently contains nearly 8,000 amphibian species, of which nearly 7,000 are frogs and toads, just over 700 are newts and salamanders, and more than 200 are caecilians. New species are being discovered every year. At the same time, about half of amphibian species are in decline, while a third are already threatened with extinction. In the past two decades, nearly 170 species have become extinct. In effect, among vertebrates, amphibians are currently the class most at risk.

Amphibians are found on all the continents except for Antarctica. Brazil is the country with the most amphibians species, with just over 1,000, Colombia has nearly 800, followed by Equador and Peru, with more than 500 each. Canada lays claim to only 40 or so, with 24 species in Ontario. All our provinces and territories have one or more species. For more information on Canada’s amphibians, see Simply Wild Canada (

Amphibians can be found in a wide variety of habitats. Most species live on the ground, in the ground, and in trees close to freshwater aquatic ecosystems. Although most amphibians start as larvae living in water, some species have developed behavioural adaptations to avoid this phase, specifically the seepage salamander and many of the nearly 400 lungless salamander species.

Despite forming a small percentage of the total animal biomass, amphibians nevertheless play an important role. They control insect populations, including mosquitoes and other pest species. Tadpoles improve water quality by controlling the growth of algae and foraging on detritus that builds up as sediment on the lake or river floor. Left unconsumed, the algae and detritus can deplete oxygen in the water. Amphibians, at various stages of development, also form an important food source for animals higher up on the food chain. Wasps, spiders, shrimp, fish, dragonfly nymphs, birds, monkeys, snakes, lizards, coyotes, racoons, skunks, mink, otters, foxes – and humans — depend on amphibians for food. In addition, amphibians improve soil fertility through soil burrowing and nutrient cycling, and they help to recycle nutrients in our lakes and rivers through aquatic bioturbation. Amphibian declines may also serve as a bellwether, just as fish do, for the decline of our freshwater ecosystems.

As an illustration of just how important amphibians are to us, here is an excerpt from a Sept. 2017 news item in the New Indian Express by Mike Pandey, a documentary filmmaker on wildlife and environment, titled “Decline in predators behind proliferation of mosquitoes”

News of over 60 children’s deaths at a hospital in Gorakhpur is alarming. Hundreds of lives have been lost during the past months across India, tragically most of them very young children. Encephalitis, dengue, malaria and chikungunya have returned with the monsoons, with greater force than earlier years, according to some doctors. Moreover, news of Zika, a deadly mosquito-borne virus with no cure, raising its head in Pune, is spreading fast.
In Gorakhpur, over 25,000 young children have died of encephalitis since the first outbreak in 1978. Despite the regular fogging of colonies by government agencies, we are losing the war. No matter what, fresh waves of mosquitoes emerge daily. One of the reasons for the increased density and proliferation of mosquitoes is the absence of their natural bio-eliminators—frogs, toads, dragonflies, water spiders and other life forms that form the food chain of the aquatic ecosystem. For centuries, frogs and toads have kept the vector population under control. No manmade solution can match nature’s natural defence system. But in our greed and ignorance, we fractured nature’s protective food chain. We ate up most of the frogs, destroyed our wetlands, home of amphibians and aquatic life, by building colonies over them, and wiped out the rest by poisoning water bodies with pesticides and fertilizers.

In the absence of frogs and water spiders, mosquitoes and other water insects and parasites have proliferated. Their larvae kept mosquito populations under control. Frogs and toads breed during the monsoons—the same time as mosquitoes—and help maintain the aquatic ecosystem. India, along with Bangladesh, was the largest exporter of frog legs in the world during the ’80s, exporting over 10,000 tonnes of frog legs (roughly over 1.5 billion frogs) annually. This led to the near total decimation of frogs and toads.

Fortunately, a ban in 1983 put a stop to the mindless harvest of the amphibians. The demand for frog legs still continues. Indonesia is the largest supplier today. Over 5,000 tonnes of frogs are still consumed globally. Besides, rampant use of pesticides, chemical effluents and fertilizers has wiped out the frogs and a host of aquatic life forms. The mosquito epidemic is manmade and a direct result of our activities and callousness towards nature and life forms that we share space with. An effective and positive step would be to work towards restoring the aquatic ecosystem and habitat by cutting down on discharge of chemical effluents directly into rivers from factories and illegal industries operating along our rivers and lakes. (end of quote)

And then of course, amphibians have served as an inspiration in art and literary works, and the traditional-medicine lore of many cultures. Civilizations all over the world have paid tribute to frogs, toads and salamanders, from ancient Mesopotamia, through old Indian and Chinese proverbs, Peruvian art, Aesop and his fables, the Brothers Grimm, to Kenneth Grahame’s The Wind in the Willows (who can forget the inimitable Mr. Toad!), MC Escher’s frog-themed tessellations, and Sesame Street’s Kermit. Last but not least, they have contributed greatly to scientific research, whether as lab specimens or as a source of analgesics and anti-viral drugs, or a key to regenerative biology. In fact, one-tenth of all studies that have won a Nobel Prize in Medicine and Physiology used frogs in their research.

So what are the threats to the survival of amphibians? Some of the greatest threats are diseases like chytridiomycosis; loss and alteration of habitat; and pollutants like fertilizers and pesticides, which are endocrine-disruptive. Other threats are destruction of the ozone layer, introduced species, and over-exploitation by humans.

The greatest threat of all is climate change. Amphibians have many disadvantages in this respect. They are especially sensitive to changes in temperature and other alterations in their environment because of their unshelled eggs, highly permeable skin and unique lifecycle. The shallow ponds and waterways, so vital for both amphibian breeding and the survival of young tadpoles, are drying up in our warming climate. Adults trying to move to new ground can often end up as roadkill or in an environment where they are unable to find food and reproduce.

Globally, some efforts are being made to stem this crisis. The Amphibian Conservation Action Plan, released in 2005, and developed by over 80 experts, detailed the actions required to reverse amphibian declines over the next 5 years, and the associated costs. This plan continues today, and includes efforts to create zoos to generate assurance colonies of threatened amphibians, organize rescue and conservation projects for those living in the wild, and support research. Numerous other organizations have formed to address this crisis: Save the Frogs!, the Amphibian Foundation, the Association of Zoos and Aquariums, FrogWatch (a program supported by Nature Canada), and the Amphibian Survival Alliance, are just some of them. In addition, other well-known environmental groups, such as the World Wildlife Fund, the Nature Conservancy of Canada, the Sierra Club, also conduct campaigns to protect endangered amphibians.

How are amphibians faring in Ontario? Well, 7 out of the 24 species are now endangered. One reason is that several of these species are not naturally abundant in this province, with it being at the northern limit of their range. If you factor in the causes mentioned earlier in this article – habitat fragmentation and destruction, the chytrid fungus, road mortality, terrestrial and aquatic pollutants, and climate change – you have a recipe for further declines in this vital part of our ecosystem.

Ontario Nature, a conservation organization that protects wild species and habitat through conservation, education and public engagement, recommends the following steps to try to stem this decline:

First of all, our federal and provincial governments need to produce and coordinate a comprehensive, regularly updated inventory of amphibian observations to better identify, conserve and manage species at risk; produce an atlas of amphibians; and improve public awareness of the threats to these species, and conservation solutions. Individuals can assist in this objective by submitting amphibian sightings as part of Ontario Nature’s atlas project. More information on how to do this can be found on this link:

There are so many other ways to help! Both individuals and municipalities can avoid and discourage the in-fill of wetlands, maintain and enhance natural shorelines, provide unmowed buffer zones around ponds and along streams, discourage the use of pesticides and excessive amounts of fertilizer, adopt a local amphibian species as the “official” one for our community, and support our county’s stewardship council, local field naturalist clubs, and other conservation organizations. MVFN (Mississippi Valley Field Naturalists), MMLT (Mississippi-Madawaska Land Trust), and the MVCA (Mississippi Valley Conservation Authority) provide all kinds of environmental education programs for people, including children. The MVCA organizes summer day camps for children at the Mill of Kintail that incorporate a rich curriculum full of outdoor nature-focused activities. MVFN provides an Environmental Education Program for children at the Mill of Kintail during the school year, and organizes monthly lectures by experts on a variety of environmental topics, which take place at the Almonte United Church. MMLT organizes regular nature events on the land-trust properties it manages. Municipalities can also install barriers and underpasses to help guide animals safely away from, or under roads.

As individuals, we can avoid the use of off-road vehicles in sensitive habitats like shorelines and shallow wetlands. These habitats are home to many amphibian species, and ATV or snowmobile use in such areas kills adults, including hibernating amphibians, and damages their nests and habitat. We can also leave fallen wood on the forest floor, or scatter a few untreated pine boards for salamander shelter, and provide rock piles in sunny locations.

Roadkill is a serious threat to both reptiles and amphibians. Keep a lookout for these animals and stop – if it can be done safely — to help them cross the road, in the direction they’re already going. At the very least, do your best not to run them over. One way is to simply avoid driving on warm, rainy nights. Never remove native amphibians from the wild. Doing so is a serious threat to many species, and is illegal in many cases. Never release a non-native or “pet-store” animal, or any non-native plants, into the wild. We are already suffering from such released animals as the Asian goldfish (located in Lake Erie, Lake Ontario and occasionally in other locations in Ontario), and the red-eared slider turtle (now in the Toronto area). Many of Ontario’s waterways have been invaded by aquarium plants such as the Eurasian water milfoil (found in all the Great Lakes, and many inland lakes throughout southern and central Ontario), the European water chestnut (now in the Ottawa River), and the water soldier (identified in the Trent River). Finally, always ensure that your dog is on a leash when walking in the woods; prevent your cats from killing frogs, toads and salamanders by keeping them away from natural areas; and leave beaver dams in place.

Many of the steps we’re already taking to reduce pollution, make more efficient use of our resources, and protect and improve natural areas for other creatures and plants with whom we share this planet, will also help our frogs and toads and salamanders. Let’s do what we can to nurture these fascinating helpmates of ours!




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