Photo: The value of biodiversity and its impacts on human health

We share the Earth with more kinds of organisms today than ever before (Credit: Karim Rezk via Flickr).

By Tina Fujikawa and Joseph Dougherty, MD

Docs Talk logoMay 22 is the International Day for Biological Diversity, marking the day on which the United Nations adopted the Convention on Biological Diversity in 1992. In the past two decades, the scientific community's understanding of ecology — the study of how ecosystems work and where each biological component of a system fits into the greater whole — has exploded. With that knowledge has come two key realizations; firstly, that we are losing worldwide biological diversity (biodiversity) at an alarming and unprecedented rate, and secondly, for humans to thrive or even survive in the future, we must preserve as much biodiversity as possible so that we do not limit our future options.

The health of the natural world is often measured by examining the distribution and health of the many plants and animals who share this planet with us. This gives scientists a picture of the planet's biodiversity: the sum of variations of all life within a given ecosystem. Ecologists have shown that the healthier an ecosystem is, the more diversity it will contain. Heavily damaged or polluted ecosystems contain far fewer kinds of plants and animals than natural, undamaged systems of the same type. Thus, monitoring trends in biodiversity is like listening to the heartbeat of the planet.

More kinds of organisms inhabit the Earth today than ever before. The phenomenal diversity of organisms and cultures on Earth today is the result of more than 3.5 billion years of biological evolution. And through the millennia, each living thing has adapted to meet the demands of the habitat in which it lives. When physical forces (volcanoes, earthquakes, glaciers, droughts, floods, etc.) change the character of a region, changes also occur in the array of organisms that dwell there, including humans. Biological pressures (predation, disease, starvation, competition for mates, etc.) can also influence populations or communities of organisms. A vast diversity in genes, species, ecosystems, and even cultures provides the raw materials with which populations and communities, including humans, adapt to change. The more options that exist, the more likely a solution can be found to face the next challenge — be it climate change, a new disease, or a need to produce greater agricultural yields on a limited piece of land. Unfortunately, humans are rapidly depleting the Earth of its biological treasures.

The services provided by nature, called ecosystem services, include everything from watershed protection to pollination to the flow of nutrients that wind up on our tables. Together, these ecological services contribute significant economic benefits to human welfare. In fact, the uninterrupted continuation of Earth's natural life support systems is crucial to both the success of the world's economy and the health of the human species. One study estimated these benefits at more than US$30 trillion per year, far more than the annual GNP of our planet. These are services that humans cannot replicate through any amount of machinery or ingenuity. Intact ecosystems are vitally important to human health. We derive all our food and many medicines and industrial products from the wild and domesticated components of biological diversity. From the mould that first gave us penicillin, to the many unique pharmaceutical products derived from viper venom, periwinkle alkaloids, or seafloor sponges, the Earth's biodiversity has literally lead saved human lives.

Conversely, when environments are damaged, people suffer considerably. Government studies show that elevated levels of troubling toxins, including mercury, PCB's, dioxins and synthetic compounds, have infiltrated our food chain in the past three decades. It is common to see a chemical toxin concentrated millions of times as it rises from the bottom of the food chain to the top. Throughout the industrialized world, our food sources have been seriously compromised. Chemicals, herbicides, pesticides, poisons, and pollutants of all types enter the food chain through our water, soil, and air. These environmental dangers have weakened our livers, digestive and immune systems. Environmental factors can lead to acute disease and chronic conditions such as fatigue, headaches, sleep disorders, mood swings, depression, confusion, body pain — the symptoms are nearly endless.

While the medical benefits of biodiversity are considerable and the costs of environmental degradation are severe, there are other impacts to consider. Biodiversity also holds important social and cultural values, and the economic prospects of protecting biodiversity are nearly endless, from recreation and tourism to as-yet unimagined commercial products. The vast gene bank contained in the vault of biodiversity is an insurance policy against future calamity. The loss of each additional unit of biodiversity reduces the number of tools nature can use when responding to changing conditions. This is as true for humans as for any other species, and that is why we must work to preserve and maintain our natural inheritance. As stewards for the next generation, it is our responsibility to ensure the tools we were handed by nature are still around for use by the generations that follow. Maintaining biological diversity assumes far greater urgency. Through pressures both natural and man-made, an ever-increasing number of plants, animals, and other resources are pushed toward the brink of extinction.

Dr. Joseph Dougherty has degrees from UC Berkeley and the University of Michigan and is currently a general surgeon in Northern California He uses photography as a tool to help study the natural world and communicate its wonders to a wider audience. Dr. Dougherty has spent the past two decades visiting ecological and biodiversity hotspots around the globe and chronicles many of those experiences at his website.

Tina Fujikawa completed her studies in Ecology at Cal Poly in San Luis Obispo, spending countless hours in the outdoors. She gained a firsthand appreciation for the inextricable relationships humankind has with the natural world through her studies in forensic entomology. She is now pursuing further education in public health.

May 20, 2010