A new global review published in Conservation Science and Practice highlights that reptiles living on islands are facing a higher risk of extinction compared to their mainland counterparts. The study, led by Dr Ricardo Rocha from the Department of Biology at the University of Oxford, found that 30% of island reptile species are threatened with extinction, while the overall rate for reptiles globally is 12.1%. Despite this elevated risk, only 6.7% of reptile-focused research since 1960 has been dedicated to island species.
Dr Ricardo Rocha explained the ecological importance of these animals: "Reptiles are keystone species for island ecosystems. For example, on Madeira Island - my birthplace - wall lizards are everywhere, chasing insects, pollinating plants and eating fruits. If island reptiles are allowed disappear, this would have huge impacts on many other species."
The study points out that human activities such as agricultural expansion, logging, pollution, and the introduction of invasive species have contributed significantly to population declines among island reptiles. Many evolved without mammalian predators and therefore lack strong defensive behaviors. Dr Rocha added: "Many island reptiles evolved in the absence of mammalian predators, so they haven’t developed strong defensive behaviours. This makes them easy targets for predators such as free-ranging cats, which are a leading cause of extinctions on islands. On Madeira Island, our research found that a single cat can eat more than 90 lizards in just one year - a striking example of how introduced predators can upset fragile island ecosystems."
The researchers analyzed data from publications between 1960 and 2021 and discovered that larger and more widespread species receive most scientific attention. In contrast, smaller or recently described high-altitude island species often remain unstudied. Sara Nunes from the University of Porto said: "Many of the world’s most distinctive reptiles - those that evolved in isolation on islands - are the least known. This knowledge gap is especially concerning because these species often have small ranges and face intense human pressures."
The authors attribute this disparity to factors such as remoteness and accessibility challenges faced by researchers working on islands, funding priorities favoring charismatic or medically significant reptiles over less-known ones, and greater investment in tourism infrastructure rather than biodiversity science in wealthier island nations.
To address these issues, the study recommends prioritizing targeted research on at-risk island-dwelling reptiles with little or no existing data; fostering collaborations between national institutions and local communities; incorporating information from NGOs and government agencies; and integrating non-English language studies into global reptile research.
Examples cited include Madagascar—which hosts over 450 reptile species despite covering less than 0.4% of Earth's land area—and the Indo-Malayan region identified as a hotspot for diversity but lacking sufficient scientific study.
Dr Rocha concluded: "As the biodiversity crisis deepens, understanding and protecting island reptiles has never been more urgent... Focusing scientific and conservation efforts where they are most needed - e.g., on islands and their unique reptile species - is essential to prevent irreversible losses. Imagine visiting Komodo Island and not seeing its dragons. It just wouldn’t be the same, would it?"
The research involved contributions from several institutions including the University of Porto; Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) Berlin; Global Change and Sustainability Institute in Lisbon; Universidade de Lisboa; and University of Helsinki.