In the 1960s, scientist James Lovelock developed and articulated the controversial Gaia hypothesis, which suggests that the Earth’s biosphere, atmosphere, oceans, and soil act together in a feedback system that seeks an optimal physical and chemical environment for life on the planet (Lovelock 1995). In other words, he proposed that the living and nonliving parts of the earth form a complex, interacting system that
functions as a single, living, self-regulating superorganism.
Viewing photographs of Earth taken from space, one can at least emotionally, if not scientifi cally, accept the underlying concept of the Gaia theory. Floating in the universe, surrounded by its atmospheric cell wall, with its oceanic cytoplasm and terrestrial organelles, the image of Earth as a unified organism seems real enough and it is easy to imagine how serious insults to its functional integrity can disrupt planetary life. This view underscores the interdependency of the physical environment of earth and the living things that reside on and in it. Scientists are now beginning to see and understand how disruptions such as global warming, widespread deforestation, and chemical pollution of marine environments can adversely affect the health and well-being of the earth’s fl ora and fauna, including humans and domestic animals.
Gaia theory aside, numerous examples (some presented in this article) make it increasingly clear that many new diseases are emerging as a result of environmental perturbation and increased contact between humans and domestic and wild animals in disturbed environments. Full understanding of the natural history of emerging diseases and effective strategies for their control therefore require collaborative, interdisciplinary efforts of human, animal, and environmental health specialists. In other words, a proper response to the current situation of emerging disease is the One Health approach.