The World Around Us Shapes The Health Within Us

I spent much of my life looking inside the human body.

Under the bright lights of the operating room, with a knife in my hand and a human heart before me, I learned to read the signs of disease in muscle, tissue, and blood flow. I saw it in scarred lungs, narrowed arteries, inflamed valves, and weakened hearts struggling to do what hearts are meant to do. Just outside the door, families waited in that familiar space between fear and faith, hoping that skill, judgment, and grace would be enough.

The author and surgical team conducting a heart transplant in the first years of the Vanderbilt Transplant Center. Today, the Center is the busiest heart transplant center in the world.

John Howser, Vanderbilt University Medical Center

As a heart and lung transplant surgeon, I was trained to focus on the person in front of me: the anatomy, the diagnosis, the procedure, the immediate crisis. Yet over time, as I cared for patient after patient and watched the same patterns return, I began to understand something larger. The illnesses I was treating did not begin on the operating table. They did not begin when a patient arrived at the hospital short of breath, or when a scan revealed a mass, or when a blocked vessel demanded urgent intervention. In so many cases, their roots stretched much farther upstream, into the conditions of daily life and the world people moved through long before they ever entered my care.

They were shaped by the quality of water, the nourishment or emptiness in food, the burden of extreme heat, the weight of chronic stress, the condition of neighborhoods, and the health of the natural systems in which every human life is lived.

That realization changed the way I think about medicine. It also changed the way I think about nature.

For many years, we have treated human health and environmental health as separate conversations, as though one belongs to hospitals and clinics while the other belongs to forests, coastlines, and policy debates. My own life has taught me otherwise. The world around us shapes the health within us. What we now call planetary health simply gives language to something ancient and intuitive: human well-being depends upon the well-being of the living systems that sustain life.

This truth is neither abstract nor ideological. It is physiological. It is biological. It is deeply personal.

The lungs receive the atmosphere. The cardiovascular system responds to heat, pollution, and chronic strain. The immune system reacts to exposures so common they easily disappear into the background of daily life, even as they accumulate quietly over years and across populations. What surrounds us eventually enters us. What happens beyond the skin finds its way inside.

As a physician, this feels less like a revelation than a return to first principles. Life is relational. Health is shaped by connection. The water we drink, the soil that grows our food, the climate that shapes where and how we live, the biodiversity that strengthens resilience across ecosystems, all of these belong in the same frame as vaccines, medicines, and surgical care. They are part of the foundation on which human flourishing rests.

I came to medicine through science, evidence, and intervention. I came to public service through a belief that wise policy can scale healing. Through years of work in conservation and climate, I have come to see that nature itself belongs in that same frame, because it offers one of the most powerful forms of prevention we have. Nature is far more than scenery, ornament, or retreat. It cools neighborhoods, stores and filters water, buffers storms, enriches soil, supports biodiversity, and creates the conditions in which communities can thrive. In that sense, nature functions as infrastructure, resilience, and medicine all at once.

This becomes especially clear when we consider what climate change and environmental degradation mean for health. Extreme heat raises the risk of dehydration, kidney injury, cardiovascular stress, and death. Pollution worsens asthma, chronic lung disease, heart disease, stroke, and adverse pregnancy outcomes. Flooding carries contamination into homes and water systems, increasing the risk of infectious disease. Warmer temperatures expand the reach of mosquitoes, ticks, and other vectors that carry illness into places once spared. Wildfire smoke sends particulate matter deep into the lungs and bloodstream. Food systems come under strain. Sleep erodes. Anxiety grows. Mental clarity fades. What can sound, in public conversation, like a distant environmental concern becomes immediate when viewed through the lens of human health.

That shift matters. People may turn away from partisanship, but they understand a child struggling to breathe during a high-ozone day. They understand an older parent weakened by relentless heat. They understand a family whose drinking water has been compromised after a flood, or a community where repeated exposure and repeated stress slowly wear down well-being over time. Health brings the issue closer. It speaks a language of daily life, and because of that, it opens doors that other arguments sometimes leave shut.

This is one reason I have become convinced that caring for the natural world belongs at the center of any serious conversation about human flourishing. A healthy forest upstream protects drinking water downstream. Wetlands soften the force of storms before those storms reach homes and hospitals. Urban tree canopy lowers temperatures in neighborhoods where summer heat can become dangerous. Healthy soils strengthen food systems and resilience during drought. Biodiversity supports pollination, renewal, and the countless ecological relationships upon which life depends, whether or not we notice them in the moment.

Increasingly, we can measure these benefits with rigor. In Louisville, the Green Heart Project helped show that increasing neighborhood greenness can improve meaningful health markers tied to inflammation and cardiometabolic risk. That evidence matters because it grounds intuition in science. It shows that planting trees and restoring landscapes carry consequences far beyond aesthetics. These choices shape physiology. They shape risk. They shape long-term human outcomes.

In medicine, dramatic interventions often capture our imagination. The transplant. The emergency operation. The heroic rescue. Those moments matter deeply, and I have devoted much of my life to them. Yet medicine, at its wisest, has always aimed for something more enduring than rescue alone. It seeks to prevent suffering before it begins. It asks us to look upstream, to search for causes, to understand patterns, and to intervene before damage becomes irreversible.

Over the years, I found myself asking a different set of questions in the operating room. What shaped this lung before I ever touched it? What burden did this heart carry long before symptoms appeared? What exposures, habits, neighborhoods, systems, and absences helped create the disease now lying open before me? Those questions enlarged my understanding of responsibility. They reminded me that health emerges from far more than clinical care. It is shaped by community, environment, policy, culture, and the condition of the natural systems that hold us all.

This broader view also calls for humility. We have grown comfortable imagining ourselves as separate from nature, standing above it rather than within it. The deeper truth is one of dependence and reciprocity. Our lives rest upon relationships we did not invent and cannot fully command: between forests and rainfall, wetlands and coastlines, pollinators and crops, oceans and climate, microbes and soil, biodiversity and resilience. When these relationships weaken, human vulnerability grows with them.

And still, I am hopeful.

That hope is grounded in the same discipline medicine taught me. In the operating room, realism and hope live side by side. You face complexity honestly. You respect danger. You acknowledge uncertainty. Then you act, with care, focus, and determination. That spirit serves us here as well.

The challenges before us are immense, yet so is the opportunity. We have stronger science than ever before, clearer evidence, better tools, and a growing understanding that health, climate, and conservation belong in one conversation. We know that nature-based solutions, protecting forests, restoring wetlands, managing landscapes wisely, greening neighborhoods, rebuilding coastal resilience, can strengthen communities while improving health and reducing climate risk. We know that upstream investments often yield downstream healing. We know, too, that when people begin to see their own lives reflected in this story, the conversation changes.

If there is one lesson I carry from the operating room into this wider work, it is that life depends on connection. In the body, everything is connected: circulation, oxygenation, inflammation, stress, repair. The same is true in the world beyond the body. The health of a child in a city neighborhood is connected to shade, food, clean water, and the conditions of the street she walks each day. The health of a coastal family is connected to wetlands, storms, and sea-level rise. The health of a farming community is connected to soil, pollinators, rainfall, and biodiversity.

Once we begin to see those connections clearly, our obligations come into focus as well. We are called to build a society that treats nature as foundational to health, that invests upstream, that protects the systems that protect us, and that speaks about climate and conservation in language people can feel in their own lives and in their own bodies.

I learned to see disease one patient at a time, and I remain grateful for that calling. Yet medicine eventually taught me something larger: if we hope to build healthier lives, we will need a healthier world.

To care for that world is to care for one another. It is to understand that the boundaries we draw between environmental well-being and human well-being have always been far thinner than we imagined. And it is to recognize, with urgency and with hope, that some of the most powerful prescriptions for the future lie all around us, in the landscapes we restore, the communities we strengthen, and the natural systems we choose to protect.

That is where healing begins.

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Author’s Note:

As a physician, I have spent much of my career studying human health. Increasingly, I have come to believe that understanding, and protecting, the health of the planet is inseparable from protecting our own.