In 2021 and again in 2023, more than 200 scientific journals issued a rare joint call for health professionals to treat climate change and biodiversity loss as one indivisible global health emergency. This framing reflects a growing recognition that human wellbeing is inextricably linked to the wellbeing of other animals and the planet.
Encouragingly, the health sector in recent years has taken notice of climate change. In 2023, for example, a health day was held for the first time at the United Nations Climate Change Conference, or COP28. During that same meeting, more than 150 countries endorsed a declaration on climate and health and $1 billion in funding was pledged to support efforts at this nexus. The United Nations even labeled climate change “the single biggest health threat facing humanity.”
Biodiversity is equally critical to health. Defined as the variety of life on Earth, biodiversity encompasses variation within species and between species. It underpins the food we eat, the water we drink, the air we breathe, and the stability of ecosystems that regulate climate and ultimately our wellbeing. For health professionals, this means that safeguarding biodiversity is not simply an environmental concern but a foundational element of preventive and clinical care.
Unfortunately, biodiversity has not received nearly as much attention as climate change within the health sector. The COP28 declaration makes no mention of biodiversity, nor does the draft Belém Health Action Plan prepared ahead of this year’s climate conference — which, paradoxically, is taking place in an Amazonian city. The New England Journal of Medicine, the world’s leading medical journal, has a special series on climate change but none for biodiversity; a search for “climate change” on its website yields 3,000 hits; “biodiversity” produces just 17 results. This neglect obscures the reality that biodiversity loss directly influences health outcomes. Without integrating biodiversity into climate and health strategies, efforts to stabilize climate and protect public health will fall short.
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Earth’s biodiversity is vanishing at an astonishing pace. Over the past 50 years, the average size of wildlife populations declined by nearly 75%. Today, 96% of the world’s mammalian biomass consists of humans and livestock; wild mammals make up just 4%. The current rate of species extinction suggests we are living through the sixth mass extinction — this time driven not by natural cataclysms such asteroids but by a single species: Homo sapiens.
The implications for human health are profound. Biodiversity is essential for the survival of our species. It provides our basic sustenance in the form of nutritious food, safe water, and clean air; regulates infectious disease transmission; bolsters our mental health; and inspires development of blockbuster drugs.
But our dependency on biodiversity runs deeper. The web of life is delicate, and as it unravels, we face cascading consequences. Consider white-nose syndrome, a fungal disease introduced to North America that has decimated bat populations. With fewer bats to control insect populations, farmers have turned to pesticides, potentially contributing to increased infant mortality through environmental exposure. Meanwhile, in South Asia, the use of a common painkiller in cattle has led to the collapse of vulture populations. As carcasses piled up, rabies and other diseases spread more easily. Recent estimates suggest this scavenger die-off caused hundreds of thousands of excess human deaths with economic costs of nearly $70 billion per year.
Despite these examples, biodiversity loss has not galvanized the health sector like climate change has. This may be because climate impacts — wildfires, droughts, floods — are immediate and visible. Biodiversity loss, by contrast, unfolds more subtly and is often masked by urban living, which insulates many from nature’s decline. Yet cities are not immune. Biodiversity loss contributes to poor air quality, increased seasonal allergies, and the spread of pandemic-potential zoonotic infections.
The health sector must confront two major inequities stemming from its neglect of the biodiversity crisis: First, Indigenous peoples, rural communities, and other marginalized groups, who are already suffering, currently receive little support in addressing this crisis. Second, future generations face irreversible harm. Extinction is forever, and the loss of species today will erode the resilience and health security of tomorrow’s children.
To address these challenges, the health sector must integrate nature into the growing climate and health movement. Without doing so, the movement will fail to meet its mandate to save lives. Protecting and restoring nature is essential to limiting warming to 2 degrees Celsius, a threshold beyond which health impacts will escalate exponentially. Biodiversity also plays a critical role in climate change adaptation — forests blunt landslides, mangroves buffer cyclones, and urban green spaces reduce impacts of heatwaves. All that to say: Relieving human pressure on the environment is “an important medical intervention in itself.”
Several recent international achievements are paving the way for robust action. The Convention on Biological Diversity recently adopted the Kunming-Montreal Global Biodiversity Framework and the Global Action Plan on Biodiversity and Health, signaling that more than 190 countries now consider biodiversity a key determinant of human health. In 2024, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (the biodiversity equivalent of the Intergovernmental Panel on Climate Change) called for integrated action to address biodiversity, water, food, health, and climate challenges. In May, World Health Organization member states adopted the Pandemic Agreement, the first binding international agreement with obligations to address drivers of infectious disease emergence at the human-animal-environment interface.
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This momentum has even reached the highest levels of international law. The International Court of Justice has unanimously affirmed that states have obligations to address climate change because the right to health cannot be realized without a clean and sustainable environment.
These international achievements reflect growing global consensus on the need to integrate climate, biodiversity, and health. This progress, however, risks being undermined by domestic challenges in the United States, where public health and science are being dismantled at an astonishing pace.
Amid this fragmentation, nature still offers a rare opportunity to unify across political divides. While climate change has become increasingly polarizing, concerns over environmental toxins and degraded ecosystems resonate broadly with the public — which likely explain how they have become embedded in movements such as Make America Healthy Again, even if the scientific grounding of such efforts remains limited.
The challenge and opportunity for the health sector is to reclaim this space by grounding nature-health linkages in rigorous evidence, and by framing biodiversity protection as a practical, non-partisan pathway to safeguard health and rebuild trust in institutions in the post-Covid era.
Health professionals are ideally situated to translate multilateral policy commitments and growing public concern into real world impact. This begins with engaging policymakers to ensure climate policies are health- and biodiversity-sensitive and equity-focused, avoiding trade-offs that may undermine long-term resilience. Health professionals should generate and apply evidence that quantifies the health benefits of protecting and restoring nature so that conservation can be scaled. Embedding these insights into clinical practice, surveillance systems, and community health programs will extend the reach of biodiversity protection into everyday public health. Educational curricula should also be updated to reflect the interdependencies of life and to prepare future health professionals for a changing world. At the same time, funders should require and support the integration of biodiversity into all climate-health initiatives.
It took decades for the health sector to fully engage with the climate crisis — a delay that has cost lives. Meanwhile, the health impacts of the biodiversity crisis remain largely overlooked despite mounting evidence that they are just as urgent and far-reaching. To ignore biodiversity is, in effect, to “colonize the future” by passing irreversible ecological costs to generations yet unborn. Recognizing biodiversity protection as a core duty of care, health professionals must chart a path that safeguards the ecological foundations of health for present and future generations.
Neil Vora is a practicing physician, senior adviser for One Health at Conservation International, and executive director of the Preventing Pandemics at the Source Coalition. Chris Walzer is a wildlife veterinarian, the executive director of Health at the Wildlife Conservation Society, and a professor of conservation medicine at the University of Veterinary Medicine in Vienna, Austria.
