Chytrid Fungus is not the only cause of amphibian decline

Scientists have known for a long time that amphibian species have been on the decline in recent years. However, a study that links chytridiomycosis--a fungal disease that has caused massive deaths in frogs and toads in recent years--to the majority of amphibian extinctions has been found to be inaccurate. This discovery raises the question of […]

Elizabeth Meade
28th March 2020
Image: Needpix
Scientists have known for a long time that amphibian species have been on the decline in recent years. However, a study that links chytridiomycosis--a fungal disease that has caused massive deaths in frogs and toads in recent years--to the majority of amphibian extinctions has been found to be inaccurate. This discovery raises the question of what is causing these massive declines.

In 2019, a study published in Nature claimed that chytrid fungus had caused declines in 501 species of amphibians and wiped out 90 species entirely. However, when scientists recently took another look at the study, they found gaps in the data linking the disease to the declines and extinctions--suggesting that the cause of amphibian decline lies elsewhere. The original authors have defended their study, explaining that there are definitely other causes of extinction besides the chytrid fungus and that, because the Batrachochytrium dendrobatidis fungus was not described or understood until 1998, the lack of population surveys led them to seek expert testimonies on decline rather than hard data.

On one hand this lack of data is a symptom of a lack of concern and attention to amphibian conservation, so the authors had little choice but to seek qualitative data. On the other hand, assuming that chytidiomycosis is the main cause of death for amphibians distracts from other important causes of decline that, if recognized, could be effectively targeted and prevent more extinctions than a simple focus on curing the fungus. Other biologists and experts weighed in on the situation, claiming to understand the inconvenient scenario at hand but wishing that the authors had better expressed their uncertainty and been more clear about the implications of their sources.

Othe biologists and experts weighed in on the situation, wishing the authors had better expressed their uncertainty and clarified the implications of their sources.

"The use of concrete, replicable evidence in science is important but perhaps not straightforward when dealing with a pandemic that was at its height before the pandemic was identified," says Joyce Longcore, a mycologist with a lot of experience studying chytrid fungus. She respects both groups of scientists, both Scheele et.al., the publishers of the original study, and Lambert et.al., the group that is questioning it.

Leading amphibian conservation groups acknowledge a number of causes of amphibian decline, including but not limited to habitat destruction, introduced species that become invasive, over-exploitation, climate change, and chemical contamination. What are the causes of these issues, and why do they harm frogs?

This destruction not only impacts amphibians, but also has a negative effect on people and the environment as a whole.

Habitat is often destroyed for commercial ventures, including urban development, building roads, farming, and gaining resources such as palm oil. This destruction not only impacts amphibians, but also has a negative effect on many communities of people and the environment as a whole, making it a global human rights and environmental issue.

Invasive species, often introduced with the goal of somehow improving an environment or accidentally introduced by people who release pets, are a unique threat, in that they often disturb the food chain by eating amphibians or competing with them for food sources. Over-exploitation is the capture of amphibians from the wild to sell as pets or to use for food and medication in an unsustainable way. There are plenty of small, often Indigenous communities that use frogs in an environmentally-friendly way because they are familiar with the landscape and how to use its resources in a way that does not deplete them, but large pet, food, and pharmaceutical companies have little to no understanding of this and place profit over sustainability. Climate change is caused by a variety of factors and is also a larger issue, going beyond amphibian conservation to a problem that impacts everyone. The same could be said about the increase in chemical contamination, which often impacts people living in low-income areas near factories and nuclear plants.

Image:Flickr

With all this in mind, it seems that the amphibian crisis does not stand alone, and we will need to look beyond chytridiomycosis to fix major wildlife management, corporate, industrial, and human rights issues first, and perhaps if we do so the frogs will come along with us for the ride.

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AUTHOR: Elizabeth Meade
Science sub-ed and Chemistry major. Avid reader. Chaos theorist. Amateur batrachologist and historian. Rock fan. Likes cybersecurity and cooking.

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