Coupled nature-human (CNH) systems : generic aspects of human interactions with blooms of Florida Red Tide (Karenia brevis) and implications for policy responses
Coupled nature-human (CNH) systems are now the focus of a growing number of interdisciplinary re-search programs worldwide (Liu et al. 2007a). As implied by the term “coupled,” these systems involve interactions between nature and humans, often affecting the dynamic characteristics of each component. Natural and social scientists supported by the US National Science Foundation and other research sponsors are engaged in developing a deeper understanding of these dynamics, focusing on the linkages and feedbacks affecting the trajectories of coupled system behavior.
Human interactions with natural hazards, such as volcanoes, earthquakes, tsunamis, major storms, floods, droughts, forest fires, tornadoes, soil erosion, mudslides, sink holes, avalanches, lightning strikes, among many others, often involve such couplings. Indeed, economists who specialize in catastrophes have long defined natural hazards as comprising a process of joint production (Russell 1970, Zeckhauser 1996). Without a human presence, a natural hazard cannot impose impacts that can be measured or felt in socio-economic or other terms. In some instances, humans may contribute to the occurrence of a hazard or influence its frequency, scale, intensity, or duration. Even when humans do not cause or exacerbate a hazard, they may suffer its adverse effects, and there may be actions that can be taken to mitigate them.
This chapter focuses on a specific type of hazard-human coupling relating to coastal blooms of toxic marine algae, often referred to as harmful algal blooms (HABs). Specifically, we draw examples primari-ly from human interactions with blooms of the toxic dinoflagellate Karenia brevis from the Gulf of Mexico. Humans interact with marine algae in many ways, and the great majority of such interactions are pos-itive and beneficial. Because primary productivity drives oceanic ecosystems from the bottom up, algae provide a critical, but mostly unquantified and often unappreciated, ecosystem service to humans. Even toxic dinoflagellates such as K. brevis may serve a beneficial ecological role in terms of primary productivity and nutrient cycling (Vargo et al. 1987).