Children's Hospital Boston resident Ari Bernstein, MD, has co-written a book, Sustaining Life, linking the health of the Earth with our own health. Bernstein spent more than five years interviewing scientists and ecologists around the world and found that Earth's biodiversity (the variety of life on the planet) directly impacts our health in ways that most of aren't aware of.

Q: How did you decide to combine pediatrics and safeguarding the environment?
A: Too many of us have lost sight of our ties to the natural world and so we act as though the world is ours to spoil, as if we could degrade nature without this having any effect on ourselves. As a pediatrician, I want to keep children healthy and so this includes keeping the natural world as healthy as the one I grew up in. In short, I want people to understand that our health is inseparable from the health of the natural world.

Q: How did you decide to collaborate on this book?
A: Much has been made about other forms of global environmental change, such as climate change, in the media. But relatively little attention has been given to biodiversity loss and even less to the importance of biodiversity to health, which is really, in my view, one of the most critical subjects to address. We wrote the book because nothing like it exists and so that everyone—the lay public, scientists, policy makers—could have a compilation of the most compelling evidence of the ties between biodiversity and health.

Q: How does biodiversity affect our health?
A: For starters, about half of America's 100 most prescribed medicines are based on compounds made by plants, animals or microbes. Almost all antibiotics are derived from natural products and so are many anti-viral drugs. We also rely on biodiversity to support ecosystems, such as that of Boston's Quabbin Reservoir, which we need to purify our drinking water. The pace of current biodiversity loss is the greatest it's been in 65 million years—and is accelerating. We're losing species at a rate 100 to 1,000 times that which would occur without human influence, and when we lose a species or an ecosystem, it's gone forever.

Q: Can't we develop synthetic drugs instead of using natural products?
A: We can and do. However, if one looks at the origins of the new drugs being approved by the FDA, the majority of them—nearly two-thirds—are patterned after natural products. Many of these, such as rapamycin, a tremendously important drug for heart and kidney transplant patients, are far too complicated to be dreamed up by a chemist. And even if they could, they can be frightfully difficult to synthesize in a lab.

Q: What are some new treatments that will be lost if unless the world acts to reverse the present alarming rate of biodiversity loss?
A: We cannot possibly know what we are losing because we know so little, even today, about Earth's biodiversity. What we do know is that some of our most essential medicines, such as vincristine and vinblastine, which helped transform several nearly uniformly fatal childhood blood cancers into largely curable ones, or the statins that have proven to be one of the most important medicines for preventing heart disease, come from nature.

Q: Which species are important to medicine and at risk of extinction?
A: In the book, we highlight seven groups of organisms—sharks, bears, primates, amphibians, cone snails, gymnosperms, and horseshoe crabs—that are both threatened and have already, and could continue to—contribute to medicine if not driven to extinction. The first pregnancy test, for example, was based on a frog; if the frog ovulated after being injected with a woman's urine, the woman was told she was pregnant. Amphibians continue to be invaluable to scientists, as several new medicines, including a new, more effective kind of anesthesia, are being derived from chemicals found on frog skins. But amphibians are disappearing. Since they live in water and on land, they're doubly exposed to contaminants and pollution, and, as they often develop as tadpoles in shallow waters, their young are sensitive to ultraviolet radiation and so the ozone hole has also likely contributed to their losses. Climate change also plays a part, since they're cold-blooded and can be quite sensitive to temperature.

Q: What's another example?
A: Polar bears are so-called denning bears, meaning that they spend much of the winter months largely inactive. Before they den, they put on tremendous amounts of weight, mostly fat, and while they do become slightly insulin resistant, they don't develop type 2 diabetes. We don't know how they escape this fate. With this disease reaching epidemic proportions, it would be wise to learn what we can from the bear's physiology so that we may find better ways to treat type 2 diabetes in humans.

Some are skeptical when they hear that the polar bear might help us combat this disease. I share their skepticism but recognize that we first discovered ursodeoxycholic acid in the polar bear—a medicine used to treat a variety of ailments arising from the liver and gallbladder. It's the only available treatment for patients with primary biliary cirrhosis, a disease that uniformly leads to liver transplant.

Q: What can we do?
A: There's a whole chapter devoted to this in the book. For those of us fortunate enough to live in the developed world, we have both tremendous responsibility for maintaining biodiversity, as each of our footprints is so large, and tremendous opportunity. Living sustainably must come from an understanding that our actions reverberate around the world. This is particularly difficult for us, because we have become so successful at living apart from nature. Climate change, for example, driven by fossil fuel combustion, will push to extinction roughly a quarter of our species by 2100. That's an astounding amount of biodiversity loss for that period of time. Yet, because we do not see that some of that biodiversity that we lose may be the source of new, potentially life-saving medicines, or sustain the ecosystems that provide us with food, we have a hard time taking our energy consumption seriously.

All this points to finding ways to help people see that our livelihoods depend on the health of the natural world. For some parents, the path is easy. Think of what a parent might do if they knew that reducing their carbon footprint, cutting down on waste and protecting green space could affect their child's treatment options? If people understand what's at stake for their health, and especially their children's health, they'll find it within themselves to act in ways to preserve the world that we all need to live healthy lives.

Q: How has the reception been on the book?
A: Better than I could have possibly imagined. It's been read on every continent on Earth and it's only been around for a few weeks. For both those for whom the book's message was self-evident as well as those who are skeptical, readers have most reliably found that they could not have possibly foreseen the remarkable scope of the ways our health depends on nature.

Q: What's next for you?
A: In the coming year, I'll continue to practice at Children's while I'm a Zuckerman Fellow at Harvard and getting my master's in public health from the Harvard School for Public Health. But I'll also continue to study the affects of global environmental change on health. We have a lot of room for improvement in how we do business with the natural world and I plan on being a part of renegotiating our contract with nature.

Sustaining Life is available at amazon.com.