In British zoos and aquariums, fewer than 10% of the vertebrate species are native to the UK, and just 2% are high conservation priority, according to a study by Justin Lennon at the University of Brighton and colleagues, publishing August 19, 2026 in the open access journal PLOS One.
Although zoos were originally opened to entertain the public, over time their role in society has expanded to include education, research and conservation. However, these different duties can create conflicting priorities. For example, large, charismatic species are more likely to attract paying visitors, which are essential for a zoo's financial sustainability, but often, those species are not the highest priority for captive breeding or reintroduction programs that would fulfil conservation goals. Previous studies of zoo collections have found biases towards globally non-threatened species, but the representation of native and locally threatened species has not been investigated.
To address this knowledge gap, researchers compiled data on the species diversity and size of captive populations of vertebrates held by 113 members of the British & Irish Association of Zoos & Aquariums (BIAZA). They cross-referenced each captive species with the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, published lists of native British species and regional conservation priority lists across the UK. They identified more than 2,600 vertebrate species held in captivity in British zoos and aquariums.
Out of 106,000 captive individuals, around 61% are fish, 16% are birds, 15% are mammals, 5% are amphibians and 4% are reptiles. Fish are the most diverse group and have the highest species richness. Amphibians have the lowest diversity and the smallest number of species in British zoos, despite being the most threatened vertebrate class. Captive species classified as vulnerable, endangered or critically endangered in the IUCN Red List represent just 28.5% of the total, and their populations are less than half the size of non-threatened species. Only 9% of captive species are native to Britain, and 2% appear on one or more conservation priority list.
The results show that although BIAZA institutions have a bias towards globally non-threatened species, they are contributing to the preservation of the UK's native and priority species. However, given that conservation is a cornerstone of BIAZA membership, British zoos and aquariums could be doing more to increase the diversity and population sizes of threatened species in their collections, the authors say.
The authors add: "Conducting this research changed my own perspective. Like many people, I was aware of the criticism surrounding zoo and aquaria, and it's right that they continue to be challenged to demonstrate their conservation value. But spending years analyzing these collections also revealed how much important work takes place beyond the exhibits."
"Modern zoos are no longer simply places where animals are displayed. They have become centers for conservation breeding, scientific research, education and international collaboration, working together to safeguard species that may one day return to the wild."
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/3RBktiJ
Citation: Lennon JJ, Pernetta AP, White RL, Crooks N (2026) Taking stock: Can captive species contribute to biodiversity conservation? PLoS One 21(8): e0354602. https://doi.org/10.1371/journal.pone.0354602
Author countries: UK.
Funding: The funders Heron International provided financial support in the form of tuition fees [JJL], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the 'author contributions' section.
