By: Brittany Smith
There are about 4000 frog species in the world. The major centers of diversity are South America and Africa, Australia and New Guinea. Currently 208 named Australian species are recognised, although it is estimated that some 20-35 more are to be discovered. The fossil record of frogs extends to the early Jurassic of South America. The earliest material from Australia is of the Eocene, from Queensland. The overall morphological conservatism of frogs over such an extensive period indicates that several frog species have survived a wide range of climates and other environmental changes over at least 45 million years. The dramatic and unexplained decline of many species in recent years is, therefore, a matter of severe concern. Frog habitats are relatively unknown because in the past 200 years the Australian landscape has been altered by urbanisation, land clearing, and water diversion and pollution on a large scale. The effect of these activities on the conservation of the fauna, particularly the habitats available to species of frogs, has gone unnoticed.
There were isolated suggestions in the early 1980s that there had been declines in frog populations but no verifications were made. It was not until 1989, at the First World Congress of Herpetology in Canterbury, England, that there was any perception of a significant pattern of declines on a global basis, and any recognition of the desirability of taking steps to ensure the survival of amphibians. The Action Plan for Australian Frogs is the first attempt to provide a comprehensive assessment of the conservation status and needs of Australia's frogs, and to estimate the costs of the required conservation research and management. The Action Plan suffers from a fundamental deficiency of biological information when compared with the Action Plans developed for marsupials and birds, and also by the fact that there are relatively few herpetologists in Australia with experience sufficient to generate the information required. There is an urgent need to raise the level of commitment to the conservation of frogs and frog habitats by wildlife conservation agencies, and the level of awareness about the fauna in the general community.
Some possible reasons for these declines are thought to be due to an enormous array of human activities impinge upon the viability of frogs include insecticide use in agricultural and horticultural areas, particularly aerial spraying, land reclamation by drainage in wetland areas, resulting in loss of breeding sites, the conversion of temporary ponds to dams for stock use resulting in the destruction of peripheral sheltering sites,introduction of the Mosquito Fish Gambusia holbrooki which preys on frog eggs and tadpoles. Other factors being considered as potentially implicated in frog declines include: global changes to air and water quality, increased exposure to ultra-violet radiation caused by depletion of the ozone layer, habitat modification, impacts of introduced species, pollution, hormonally active pesticide residues, pathogens and disease, acidification and climate change, including changes in climatic extremes (Tyler 1994).
Because the cause for the population of frogs decline is uncertain, there is not much conservation poicies can mandate. At the moment, Austrailia has "recommendations" that they try to enforce. Some recommendations include, that high priority be given to research and management action to address frog declines. That research be continued into the toxicity of pollutants, particularly herbicides and their dispersants. It is also recommended that low-toxicity surfactants be required, particularly for herbicide use near water bodies and drainage lines, that research and analysis be undertaken to clarify the possible contributing role of these factors, including data already available from Australian and international studies. Examples include: pathogens, local water quality, impacts of introduced fish (eg. Gambusia holbrooki, trout, carp), impacts of introduced terrestrial predators such as cats and foxes, subtle climatic changes and perturbations, and impacts of global changes to air and water quality, and that attempts be made to determine if there are causal factors common to these declines and if any of these operate together, or even synergistically. Finally, that high priority be given to survey and research necessary to clarify the distribution, abundance and conservation status of insufficiently known species.
Sources:
Australian Government, department of the enivornment http://www.environment.gov.au/biodiversity/threatened/publications/action/frogs/6.html
9 comments:
Australia has been going through severe drought conditions the last decade, and with the Recent fires outside Melbourne I'd think that habitat displacement would be the major factor in the decline of frogs. I'm sure humans are contributing to the problem, but is this an uncontrollable event causing loss of habitat?
Another thing to think about is the amount of prescription drugs and antibiotics that currently cycle through the groundwater. The US Geological Survey ran an extensive study that showed many of these chemicals contaminate drinking water and treated water that cycles back into the environment. Could biomagnification of these hormones that are found in prescription drugs be affecting the frog populations, as well as other species?
Poor frogs, It would be really interesting to find out what factors are affecting their populations the most. Besides just putting more money into research, I really like the idea of advising locals on what they can do to protect frog species even more! Sometimes the best way to solve an issue is by putting power in the hands of all people, even if it is just a little bit at a time. They can spread the word to their neighbors, families and friends and then lots of hands will be supporting the frogs!
yes, frog populations all around the world as well as in Australia are getting smaller at an alarming rate.
Frogs absorb air and water through their skin, so they are the first to be affected by a polluted environment - they are affected by pollution of water, land and air because they live on land and in the water. They are also affected by loss of habitat, particularly those species that live in very particular habitats, such as a specific mountain for example
I lived in Australia last spring and studied many environmental problems. They are directly affected they the ENSO/ El Nino cycle, and climate change is increasing the frequency of the ENSO/El Niño events. South eastern Australia has been in severe drought for 12 years! While I was there I experienced the devastating bush fires while I lived in the South east , and toward the end of my stay I was in a very scary massive flood in South Queensland in the rain forests. The day I left I barley made it out ( by a half an hour!!) of Northern New South Whales before the roads washed out and my town was isolated for 5 days!! Australia is constantly in a cycle of drought or flood, which is partially their natural climate but definitely become more frequent as the climate changes. Another major factor on Australian ecosystems is fire suppression. That ecosystem is supposed to burn frequently and Aboriginals used fire management to control and regenerate the ecosystem, since Europeans arrived fire has been suppressed which has greatly affected the biodiversity and also was a factor in how extreme the south eastern bush fires were spring '09.
To expand on Julie's comment, prescription drugs seem to be a huge, and as yet largely unaddressed problem. In our own Boulder creek (which is darn CLEAN and well managed by any standard; particularly as compared to waterways that pass through metropolitan areas) there are a large number of "intersexed" fish south of the outflow of the waste water treatment plant. This is due to high levels of estrogen (from birth control) in the water. This obviously hurts the reproductive capacity of the fish population. If it can happen here, in our first use, virgin, well managed stream, God help the fish further down stream.
Frogs can be viewed as an environmental indicator, much like a canary in a mine. Frogs seem particularly vulnerable to the slightest environmental change. Perhaps their decile should be taken more seriously. The relatively low levels of toxins that are potential affecting these frogs could soon be a problem for other animals including humans if precautions are not taken.
It is interesting to know that Frogs can be viewed as an environmental indicator.not only frogs but the biodiversity and ecosystems are very important on the earth.
Frogs are a huge warning species for climate change and well as human impacts to the environment. Recently there has been a fungus that is affecting frogs around the world that is absorbed by there skin. This fungus could have become rampant due to warming temperatures that are more suitable for it. It also could be from human ships and boats carrying it from different parts of the world and becoming an invasive species.
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