By Deepu Sivadas, on 10 April 2026.
This week offered two observances that, at first glance, seem to speak in different voices. World Health Day 2026 called for us to stand “Together for Health, Stand with Science.” Homoeopathy Day followed with its emphasis on “Sustainable Health.” One is rooted in the language of global public health, the other in a tradition that often speaks of balance, continuity, and care. Yet both, in their own way, point to the same larger truth: health is never isolated. It is shared, connected, and shaped by the world we live in.
Seeing these themes side by side made it difficult not to think of an even larger picture: One Health. It is not a slogan to be used only when a zoonotic disease makes headlines. It is a way of understanding that human, animal, and environmental health are inseparable. When one weakens, the others begin to strain. When one is protected, the others often benefit too. In that sense, One Health is not a separate discipline so much as a reminder of something obvious that we too often forget.
Today, One Health is usually discussed in moments of urgency. Outbreaks of SARS, MERS, H1N1, Ebola, Zika, and COVID-19 put it in the spotlight, making one thing unmistakably clear: the boundary between people, animals, and ecosystems is far more porous than we once assumed. Diseases do not emerge in a vacuum. They are shaped by land use, habitat loss, climate change, wildlife trade, livestock practices, pollution, and the many ways in which human activity reshapes natural systems.
That is why One Health should not be spoken of only when the next outbreak begins. If we wait for the disease to appear before we begin talking about the connections, we are already too late. The real work lies in the quieter, less dramatic choices that happen long before a crisis reaches the news cycle — how forests are cleared, how wetlands are drained, how rivers are polluted, how cities expand, and how livestock production intensifies at the edge of fragile ecosystems. These are not only environmental concerns. They are health concerns, too.
And yet, this is where the conversation often becomes incomplete. Formally, One Health has always had three pillars: humans, animals, and the environment. In practice, however, the environmental pillar is the one most often left in the shadows. Human and veterinary health tend to dominate the discussion, while ecosystem health is brought in later, if at all. This is a pity, because the environment is not a background setting for health. It is part of the health system itself.
A degraded forest, a polluted river, a shrinking wetland, or a stressed coastline is not only a conservation issue. It is a warning sign. Such changes affect air quality, water security, food systems, disease ecology, and the resilience of communities living closest to the land. The environmental dimension of One Health is therefore not optional or secondary. It is the foundation on which the rest rests. When that foundation weakens, no amount of downstream intervention can fully make up for the loss.
This is why One Health matters so deeply to conservation. For institutions such as IUCN and, in particular, the Commission on Ecosystem Management, One Health is not an external idea borrowed from public health. It is closely aligned with the very work of ecosystem-based management, resilient landscapes, and socio-ecological balance. CEM’s mandate already speaks to the kind of thinking One Health demands: looking across boundaries, connecting systems, and understanding that the well-being of people depends on the well-being of nature.
In South Asia, this connection is especially visible. The region carries dense populations, rapid land-use change, rich biodiversity, and deep dependence on natural resources. Here, the consequences of environmental decline are not abstract. They appear as floods, heatwaves, landslides, vector-borne diseases, crop failures, air pollution, and water stress. These pressures do not arrive separately. They move through the same landscapes, affecting people, animals, and ecosystems together.
That is why One Health should be understood not just as a disease-prevention framework, but as a broader ethic of stewardship. Protecting wetlands can reduce flood risk and improve water quality. Conserving forests can regulate climate, support biodiversity, and reduce the spillover risks that come with disturbed habitats. Thoughtful coastal management can buffer storms and sustain livelihoods. These are not merely environmental interventions. They are health interventions in the truest sense.
If One Health is to mean something more than a phrase repeated in conferences and policy notes, it needs to shift from reaction to prevention, from crisis to continuity, and from isolated expertise to shared responsibility. Environmental signals should be treated as part of health intelligence, not as background noise. Land-cover change, water quality, wildlife health, ecosystem integrity, and climate stress need to be woven into risk assessment and decision-making. Conservationists, ecologists, public health professionals, veterinarians, Earth observation experts, and local communities all have a role to play in that effort. It should be a welcoming space for everyone, where there’s no room for bureaucracy or hierarchy.
There is also a governance lesson here. Cross-sector collaboration works best when environmental institutions are included from the beginning, not consulted only after the problem has already escalated. If One Health is serious about addressing root causes, then environmental voices must have equal standing in the conversation. Otherwise, the framework risks becoming narrow again, focused on symptoms rather than systems.
Perhaps most importantly, the language around One Health must change. It is easy to speak of emerging pathogens, security threats, and emergency response. It is harder to speak with equal urgency about soil health, watershed restoration, urban green spaces, or biodiversity protection. But these quieter investments are the ones that keep societies resilient. They are not side issues. They are the slow architecture of health.
That is where the themes of World Health Day and Homoeopathy Day begin to meet most clearly. “Together for Health” and “Sustainable Health” are not separate ideas. They both point toward interdependence, toward balance, and toward the recognition that human well-being cannot be sustained by ignoring the systems that support life. Science reminds us of the connections. Tradition, at its best, reminds us of the need for balance. One Health gives both a shared language.
The deeper message, then, is simple. We cannot talk honestly about health while treating the environment as an afterthought. We cannot speak of sustainability while degrading the systems that make life possible. And we cannot claim to stand with science if we ignore what science has already told us: that people, animals, and ecosystems live in one connected world.
Several authors have gone so far as to call the environment “the most neglected part of the One Health triad”. Perhaps it is time to say this more plainly. One Health is not a theme for outbreaks alone. It is a way of seeing the world every day. It is present in the way we manage land, water, forests, coasts, farms, and cities. It is present in the choices we make about development and conservation. It is present in the health of the air we breathe and the water we drink. And it is present, whether we acknowledge it or not, in every effort to build a healthier future.
That is why the environment must no longer remain the neglected part of One Health. It is not the last piece of the puzzle. It is the piece that holds the others together.
Dr Deepu Sivadas is a Scientist with the Forest Ecology and Biodiversity Conservation Division at Kerala Forest Research Institute, India. He is also South Asia Regional Chair for the IUCN Commission on Ecosystem Management.