It is a common misconception that reptiles are hardy. In fact they are susceptible to multiple threats.
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A scaly crisis: why we must act now to save reptiles
by Anna Taylor
Anna Taylor summarises the findings of the most extensive research ever conducted on the global status of reptiles, and argues that if conservation continues to focus too heavily on 'charismatic megafuna', we face losing countless reptile species forever.
3 critically endangered species that the authors assessed are now believed extinct
Reptiles have inhabited our planet for more than 250 million years, and are adapted to almost every part of it. Yet when it comes to conservation action, reptiles all over the world have been overlooked in favour of more charismatic animals. With only 35% of described reptile species evaluated for the IUCN (International Union for the Conservation of Nature) Red List of Threatened Species, no one knew to what extent reptiles were being affected by our current extinction crisis.
However, a study recently published in the journal ‘Biological Conservation’ has highlighted the perilous state many reptiles are in, and calls for more to be done to protect them. The study was the result of collaboration between scientists at the Zoological Society of London and experts from the IUCN Species Survival Commission. Over 200 experts assessed a random selection of 1,500 species (out of a total of 9,084 known species), representing each group of global reptilian diversity.
It has made science history by being the first ever assessment of the extinction risk of reptiles on such a scale. The study’s authors also produced the first global species richness and threatened species richness maps for reptiles in order to show the key regions, taxa and threats by man that must be urgently targeted in order to conserve these species.
In total, 19% of all reptile species are threatened with extinction (see fig.1). Of this total, 12% are Critically Endangered, 41% are Endangered, and 47% are Vulnerable (in order of magnitude of danger, as categorised by the IUCN). Also, 7% of reptiles are in the Near Threatened category, meaning that they are likely to become threatened in the near future if measures are not taken to eliminate the threats they currently face.
Three critically endangered species that the authors assessed are in fact now believed to be extinct, including the Culebra Island Giant Anole, Haensch's Whorltail Iguana and a species of jungle runner lizard, Ameiva vittata. “The findings sound alarm bells about the state of these species and the growing threats that they face,” said Philip Bowles, coordinator of the Snake and Lizard Red List Authority of the IUCN Species Survival Commission.
By demonstrating that nearly one in five of all reptile species are in danger, it is hoped that this assessment will focus attention on the plight of reptiles, a group that has often been ignored by conservation in the past.
Dr Monika Böhm, lead author of the study, says: “I think first and foremost species conservation has traditionally focussed most prominently on “charismatic” species, such as large mammals and birds, and the shift towards a more holistic approach in terms of wider species coverage and whole ecosystem considerations is still relatively recent.
It might also have something to do with the common misconception that reptiles are quite hardy species – because we know them to occur in tough environments such as deserts. That is not really true though – many reptiles are very restricted in range with very specific habitat and temperature requirements, which make them very sensitive to environmental change.”
It is this environment change that has been the downfall of so many species. For terrestrial reptiles, 74% are threatened by agriculture, 64% are threatened by biological resource use, namely logging and harvesting, and 34% by urban development. Natural system modification (use of fire, damming etc) threatens 25% of species, and 22% are threatened by invasive or problematic species.
For marine and freshwater species, biological resource use (the targeted harvesting of species) is the most significant threat, affecting 87% of reptiles. Agriculture and aquaculture, urban development and pollution each impacts 43% of reptiles. The study also found that 80% of all threatened species are affected by more than one of these threats.
Altogether, 19% of terrestrial species are threatened – the figure is the same as the total number of threatened reptiles because the vast majority of reptiles live in terrestrial systems. Yet, when the authors looked at reptiles inhabiting freshwater and marine habitats, the percentage of threatened species jumped to 30. Dr Böhm explains:
“There are not very many marine reptiles in our sample, so the main signal here comes from the freshwater species. Freshwater systems worldwide are under immense pressure, with threats from pollution, water course management, harvesting of resources. It is a consistent picture that we see freshwater species to be overall worse off than terrestrial species. For reptiles, the added issue comes from the large contribution of freshwater turtles and terrapins to our freshwater sample – these species are also under pressure from harvesting, for example for the pet trade.”
When considering freshwater turtles alone, the scientists discovered that 52% are threatened.
Geographically, the Tropics are where the highest proportion of threatened species are found, particularly in Oceania, but the Tropics are also home to the highest proportion of species listed as Data Deficient (the IUCN places species in this category if there is insufficient data to make a conservation assessment). Clearly there are still gaps in our knowledge of the status of many reptiles, nevertheless this study has certainly provided an initial assessment from which further research can develop.
“This present study gives us a snapshot of how reptiles are currently doing. For our ongoing work on tracking changes in biodiversity, we need to establish what is happening to reptiles over time and this involves us drawing up a baseline against which to compare our current picture of reptile extinction risk… For on-the-ground reptile conservation, I think the next step is to take the message from this paper to make sure the needs of reptiles are included in conservation decisions, i.e. when focussing funding, when establishing protected areas, and so on.
Specifically, because habitat loss is such a major contributor to extinction risk in reptiles, it is vital that both habitat protection and restoration projects are carried out and that these projects consider the specific microhabitat requirements of as wide a range of species as possible, and this includes reptiles,” said Dr Böhm.
Reptiles play vital roles in the functioning of ecosystems: as predators they control their prey populations, and as prey themselves they provide a vital food source for birds and mammals. They serve as useful biological indicators for the health of their environment. However, their small home ranges, low dispersal ability, morphological specialisation and thermoregulatory constraints mean that they are especially sensitive to the changes we make to their habitats. In order to reverse their declines, we must tackle these threats and, when conservation decisions are made, never fail to remember the reptiles.
Fig.1 percentage of threatened species by taxa.
Anna taylor is a freelance conservation journalist, and chief blogger for http://conservation-jobs.co.uk
Image of chameleon courtesy of www.shutterstock.com
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