Beyond numbers: Prioritizing population health in the next era of wildlife conservation
Conservation efforts have led to significant recoveries in the population numbers of many endangered species, including the Siberian crane (Leucogeranus leucogeranus). However, how to accurately evaluate conservation effectiveness has become a new global challenge. A persistent misconception in conservation practice is the overemphasis on population numbers while overlooking population health. In this perspective, we argue that population numbers alone is an insufficient indicator of conservation success. Using the case of the Siberian crane at Poyang Lake, we highlight emerging concerns: although population numbers have increased substantially, the species now faces high ecological and health risks due to habitat degradation, artificial land use, and increased disease exposure. A growing proportion of the population is now concentrated in agricultural habitats, such as rice paddies and lotus ponds, where exposure to pesticides, microplastics, and cross-species pathogens is elevated. We propose a multidimensional framework for assessing population health, integrating physiological, genetic, demographic, disease-related, behavioral, and environmental indicators. This paradigm shift is essential to ensure that endangered wildlife populations are not only numerically recovering but also resilient and viable in the face of growing environmental challenges.
Emerging challenges on wildlife conservation
The stability of wildlife populations is fundamental to sustaining global biodiversity. Yet, the WWF Living Planet Report 2020 revealed that populations of mammals, birds, amphibians, reptiles, and fish have declined on average by nearly two-thirds in less than half a century.1 This dramatic loss is largely driven by habitat destruction, climate change, and other anthropogenic pressures. To mitigate such declines, governments worldwide have invested heavily in conservation, from financial commitments to reforms in protected area management. However, evaluating the effectiveness of these efforts requires assessment frameworks that are objective, precise, and comprehensive. Traditionally, recovery targets for endangered species have been defined almost exclusively by population numbers (i.e., headcounts). Yet mounting evidence shows that numbers alone provide an incomplete picture of recovery, overlooking essential dimensions such as functional integrity, genetic diversity, and habitat connectivity. To address this gap, the IUCN launched the Green Status of Species in 2021, offering a framework to assess population recovery and conservation success.2 The IUCN Green Status of Species represents an important step toward measuring conservation recovery, but its broad framework can be difficult to operationalize. Ambiguous baselines, high data demands, and limited taxonomic coverage restrict its application to a small subset of species. As such, the Green Status provides valuable vision but limited practical guidance, underscoring the need for complementary, fine-grained indicators that better capture conservation effectiveness.
After the COVID-19 pandemic, health-related concepts have proliferated across disciplines, with terms such as One Health and Healthy Aging gaining prominence. It is well established that nearly 70% of human emerging infectious diseases originate from wild animals.3 Conducting health assessment and research on wildlife is therefore essential not only for their conservation but also for safeguarding human public health, which reflects the philosophical concept of the harmony between humans and nature.4,5 Nevertheless, conservation biology has traditionally emphasized overall population numbers while paying comparatively little attention to the health status of populations themselves.
