A publication in Ecological Monographs

Major decline of amphibians, even in areas suitable for their conservation


A study launched in Montenegro by Mathieu Denoël and Benjamin Lejeune, researchers at the FOCUS Research Unit (Faculty of Sciences) of the University of Liège, sounds the alarm about the catastrophic situation faced by amphibians, even in landscapes that might seem adequate to their conservation. The results were published in the journal Ecological Monographs.


hile natural landscapes are supposed to be environments conducive to the persistence of biodiversity, ensuring the protection and survival of species, it is a fact that in all corners of the globe, reports of declining and extinct populations and species are accumulating. Habitat fragmentation and destruction, landscape modification, climate change and the introduction of exotic species are all factors linked to human activity that are gradually leading to the decline of such populations.

In the framework of a monitoring study of key amphibian populations conducted in Montenegro - a country in the Balkan region characterised by a vast expanse of wilderness and traditionally managed areas -  Mathieu Denoël, FRS-FNRS Research Director and Benjamin Lejeune, both members of the UR FOCUS (Faculty of Sciences) of the ULiège, made a sad assessment on the status of these populations while quantifying and explaining the causes of the decline.

This environment was indeed very favourable to several species of amphibians, as shown by old observations. Particularly noteworthy is the fact that this region was considered a hotspot of diversity for an amazing differentiation process: the presence of numerous populations of paedomorphic newts, capable of foregoing the metamorphosis so characteristic of most amphibians and thus able to reproduce while retaining the larval gills. Researchers in Liège have been able to rely on the knowledge and monitoring of these populations for many decades by local researchers, including researchers from the University of Belgrade who collaborated on this new study. Complementary expertise acquired through various international collaborations has made it possible to study the impact of various environmental factors on amphibian populations across the country over a period of nearly 70 years.

DENOEL Fig Tritons Alpine (a) and Greek (b) paedomorphic newts, i.e. retaining larval characteristics at the adult stage (Ecol. Monogr. 2019: e01347).

The results of this study, published in Ecological Monographs, are obvious and catastrophic. Researchers estimated a major decline in populations, with a 78% loss of the rarest phenotype (paedomorphic) and a 48% loss of the most common phenotype. In terms of aquatic surface area, this means a decrease of more than 99% of the occupied habitat in almost 70 years" explains Mathieu Denoël. It is in fact the most peculiar populations, endemic to high-altitude lakes, that have been particularly affected ». On the basis of multivariate analyses, the researchers have identified a major determinant that explains this decline: the introduction of non-native fish into water bodies (lakes or ponds). "Up to six species were introduced into the same habitats, leading rapidly to the decline of native species, while most other environmental factors had no major influence in this case. »

The researchers therefore quickly came to a definitive conclusion. While the preservation of terrestrial landscapes is essential to amphibian conservation - because it is what allows a rich diversity to be maintained - we must not forget the importance of preserving aquatic habitats in which simple acts, which may seem trivial or anecdotal such as the introduction of fish, can lead to a loss of global diversity.

The problem identified in Montenegro is an example of this while the country is still relatively unaffected by other anthropogenic threats and where the preservation of the traditional or natural habitats has most certainly curbed the influence of other global changes. In environments more disturbed by the abandonment of ponds, increasing urbanization, changing agricultural practices or in the face of climate change, the fate of many amphibians is increasingly uncertain. Multi-factorial and long-term analyses in these anthropized environments remain unfortunately rare in order to identify all the determinants of biodiversity loss.

This research was financed by the Fonds de la Recherche Scientifique (FNRS), the University of Liège (in particular through the Fonds Spéciaux de la Recherche, the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA), ) and the Ministry of Education, Science and Technological Development of the Republic of Serbia.

Scientific reference

Denoël, M., Ficetola, G.F., Sillero, N., Džukić, G., Kalezić, M.L., Vukov, T., Muhovic, I., Ikovic, V., Lejeune, B., 2019. Traditionally managed landscapes do not prevent amphibian decline and the extinction of paedomorphosis. Ecological Monographs 89, e01347.
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Mathieu DENOËL

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