ABSTRACT
Environmental variability, which we define as the variability in any environmental factor that affects the distribution, growth, and survival of organisms in nature (e.g., temperature, water, light, nutrients, or food), occurs at many temporal and spatial scales. Temperature at a given location, for example, varies on very short timescales (minutes to hours) depending among other things on cloud cover and shading; it also varies diurnally with colder night temperatures; it varies between days according to local weather conditions; it varies seasonally; it varies between years, decades, centuries, and millennia. Temperature also varies over short distances depending on microtopography and at larger spatial scales. The spatial and temporal sources of variability in temperature and other geophysical variables are being studied intensively in climatology (e.g., Koscielny-Bunde et al., 1998; Weber and Talkner, 2001), oceanography (e.g., Powell, 1989; Zang and Wunsch, 2001), and in river hydrology and geomorphology (e.g., Rodriguez-Iturbe and Rinaldo, 1997; Hubert, 2001). Striking similarities in the scaling of variability are emerging across a wide range of fields (e.g., Halley, 1996; Havlin et al., 1999).
