07 April 2009 | News story
With the accelerating loss of biodiversity, we are losing critical opportunities to understand and fight human disease, says Eric Chivian.
In the 1980s, with three other Harvard faculty members, I helped start an organization called International Physicians for the Prevention of NuclearWar, a group that won the 1985 Nobel Peace Prize. The most important contribution of the tens of thousands of physicians who became part of this federation was to help people grasp just how catastrophically destructive a nuclear war would be. We did this by translating the abstract, technical science about nuclear weapons explosions into concrete, human health terms that people could relate to, and as a result, I believe, we helped change public opinion and even public policy.
But with human-induced damage to the global environment like climate change and biodiversity loss, the level of complexity is an order of magnitude greater; the changes occur slowly and on global scales. It is therefore essential that physicians and public health professionals be involved in helping the public understand the human dimensions of environmental degradation. We have no Hiroshimas or Nagasakis to use as models. And the task is made much more difficult because most people have a fundamental misunderstanding about the environment: that they are somehow separate from it; that we can degrade the oceans, the atmosphere and the soils, and lose countless species in the process, as if this has no effect on us whatsoever. This, I believe, is at the heart of the global environmental crisis, and is the reason why more than 100 leading scientists spent the last seven years working on Sustaining Life: How Human Health Depends on Biodiversity, to help people understand our intimate connections with Nature, to make it clear that we don't have a choice about whether to protect the natural world or not. We must do so, because our health and our lives depend on it.
There are so many ways our health depends on a healthy environment, particularly healthy biodiversity and ecosystems- through controlling the spread of infectious diseases and invasive species, and providing clean air and water, and medicines. But perhaps one of the most powerful arguments for safeguarding biodiversity is that which describes its role in medical research and as a source of new medicines. More than 70,000 plant species are used medicinally, either traditionally or in modern medicine. Aspirin was originally derived from salicin, extracted from the willow tree. Cancer-fighting drugs have been derived from the Rosy Periwinkle plant, and many groups of animals frombears to sharks, provide important research models that can help us understand and fight disease.
Polar bears have become iconic figures in discussions about what we will lose with climate change, but their medical value is rarely mentioned. During hibernation, polar bears are essentially immobile, and yet they don't develop osteoporosis, which every other mammal, including ourselves, gets as a result of prolonged immobility. Osteoporosis is a huge public health problem for the elderly, resulting in more than 70,000 deaths in the US alone each year and costing the economy some US$ 18 billion annually in direct healthcare costs and lost productivity. Hibernating bears have compounds in their blood streams that may one day allow us to prevent and treat this disease. Polar bears become massively obese feeding on seal blubber prior to hibernating, but they don't develop Type 2 diabetes, as we tend to when we become obese. This is also not well understood, but must be studied in the wild. Yet we will lose this opportunity if we lose polar bears. Obesity-related Type 2 diabetes is essentially epidemic in the US, afflicting some 5% of the population and killing close to a quarter of a million people a year.
Many groups of animals, from bears to sharks, provide important research models that can help us understand and fight disease.
Cone snails are a large group of predatory snails that defend themselves and kill their prey by firing poison-coated harpoons at them. There are thought to be around 700 cone snail species and each one is believed to make 100- 200 distinct toxic compounds. These toxins have been intensively investigated by researchers for new medicines. Only about six species and about 100 toxins have been studied in detail, and already several important new compounds have been found. One has been synthesized as a painkiller and is being marketed as Prialt, used for the treatment of severe chronic pain that is not responsive to opiates. Morphine has been our most effective painkiller but Prialt is a thousand times more potent and even more importantly, it doesn't cause addiction, or tolerance-the state whenmoremedication is needed to achieve the same effect. The use of potent painkillers from cone snails that do not cause tolerance is a watershed in medicine, equivalent in some ways to the discovery of penicillin. Some believe that cone snails may provide more leads to important medicines than any other group of organisms. And yet they live in coral reefs which are threatened by global warming around the world.
More than a third of all known amphibian species are threatened with extinction- yet amphibians contribute to human medicine in many ways. As just one example, the Crucifix Toad found in southeastern Australia, defends itself from biting insects by secreting a sticky, protein-based glue from its skin that hardens in seconds and catches insects, even in heavy rain. This is being adapted for the surgical repair of various types of human tissue, where there is a need for a strong, flexible, porous adhesive. Synthetic glues are strong enough, but they are generally toxic and brittle and don't allow the exchange of gases and fluids necessary for healing. Most biological glues, for example those from various proteins like albumin are not strong enough to repair tissues that are subject to shear forces, such as torn knee cartilages.
We have to make these examples more widely known, to shift global policy making onto the right path. Environmentalists and health professionals can, and are starting to form, an effective alliance in starting the process. Scientists with expertise in a wide range of disciplines, from industrialized and developing countries alike must work together to convince people, particularly decision makers, that human beings are an integral part of Nature, and that our health depends ultimately on the health of its species and on the natural functioning of its ecosystems. We hope they will develop innovative and equitable policies based on sound science that preserve biodiversity and promote human health for generations to come.
Eric Chivian, M.D. is Director of the Center for Health and the Global Environment at HarvardMedical School.
He is co-author of the Oxford University Press book Sustaining Life: How Human Health Depends on Biodiversity.