Living in an increasingly connected world: a framework for continental-scale environmental science

© The Ecological Society of America www.frontiersinecology.org T interplay between fine-scale patterns and processes and broad-scale dynamics is increasingly being recognized as key to understanding ecosystem dynamics, particularly as the number and magnitude of global change drivers increases over time (Huston 1999; Rodó et al. 2002; King et al. 2004). Cross-scale interactions (CSI) are processes at one spatial or temporal scale that interact with processes at another scale, often resulting in non-linear dynamics with abrupt threshold responses (Holling 1992; Carpenter and Turner 2000; Peters et al. 2004a, 2007). These interactions may generate behavior that emerges at broader scales and cannot be predicted based on observations at single or even multiple independent scales (Michener et al. 2001). Redistribution of material, energy, and information flow within and among spatial units (ie connectivity) is one potentially powerful explanation for these cross-scale interactions. The degree of connectivity is determined both by the spatial structure of the environment and by the way in which this structure influences the change in redistribution rate – a definition similar to one used by landscape ecologists (With et al. 1997). All ecosystems around the world are connected through a globally mixed atmosphere and, historically, regional connections existed through a variety of both biotic and abiotic processes. This connectivity has been altered through human transport of propagules, toxins, and diseases, as well as anthropogenic disturbances and changes in land use (Reiners and Driese 2003; MA 2005; Herrick and Sarukhán 2007). Thus, changes in one location can have dramatic influences on both adjacent and distant areas, either at fine or broad scales. For example, the extreme drought of the 1930s in the central Great Plains of the US interacted with cultivation of marginal croplands to generate high rates of soil erosion from individual fields, which subsequently resulted in the Dust Bowl (Figure 1). This siteto regional-scale set of events spread across the continent, to affect broad-scale patterns in soil and air quality, migration patterns, human health, and the economy (Peters et al. 2004a). CONNECTIVITY CONNECTIVITY CONNECTIVITY