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[1] This paper synthesizes recent works at the interface of hydrology, geomorphology, and ecology under an integrated framework of analysis with an aim for a general theory. It addresses a wide range of related topics, including biodiversity of freshwater fish in river networks and vegetation along riparian systems, how river networks affected historic spreading of human populations, and how they influence the spreading of water-borne diseases. Given the commonalities among various dendritic structures and despite the variety and complexity of the ecosystems involved, we present here an integrated line of research addressing the above and related topics through a unique, coherent ecohydrological thread and similar mathematical methods. Metacommunity and individual-based models are studied in the context of hydrochory, population, and species migrations and the spreading of infections of water-borne diseases along the ecological corridors of river basins. A general theory emerges on the effects of dendritic geometries on the ecological processes and dynamics operating on river basins that will establish a new significant scientific branch. Insights provided by such a theory will lend themselves to issues of great practical importance such as integration of riparian systems into large-scale resource management, spatial strategies to minimize loss of freshwater biodiversity, and effective prevention campaigns against water-borne diseases.Citation: Rodriguez-Iturbe, I., R. Muneepeerakul, E. Bertuzzo, S. A. Levin, and A. Rinaldo (2009), River networks as ecological corridors: A complex systems perspective for integrating hydrologic, geomorphologic, and ecologic dynamics, Water Resour. Res., 45, W01413,

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Much of the socioeconomic life in the United States occurs in its urban areas. While an urban economy is defined to a large extent by its network of occupational specializations, an examination of this important network is absent from the considerable body of work on the determinants of urban economic performance. Here we develop a structure-based analysis addressing how the network of interdependencies among occupational specializations affects the ease with which urban economies can transform themselves. While most occupational specializations exhibit positive relationships between one another, many exhibit negative ones, and the balance between the two partially explains the productivity of an urban economy. The current set of occupational specializations of an urban economy and its location in the occupation space constrain its future development paths. Important tradeoffs exist between different alternatives for altering an occupational specialization pattern, both at a single occupation and an entire occupational portfolio levels.

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BackgroundLarge-scale inter-basin water transfer (IBWT) projects are commonly proposed as solutions to water distribution and supply problems. These problems are likely to intensify under future population growth and climate change scenarios. Scarce data on the distribution of freshwater fishes frequently limits the ability to assess the potential implications of an IBWT project on freshwater fish communities. Because connectivity in habitat networks is expected to be critical to species' biogeography, consideration of changes in the relative isolation of riverine networks may provide a strategy for controlling impacts of IBWTs on freshwater fish communities.Methods/Principal FindingsUsing empirical data on the current patterns of freshwater fish biodiversity for rivers of peninsular India, we show here how the spatial changes alone under an archetypal IBWT project will (1) reduce freshwater fish biodiversity system-wide, (2) alter patterns of local species richness, (3) expand distributions of widespread species throughout peninsular rivers, and (4) decrease community richness by increasing inter-basin similarity (a mechanism for the observed decrease in biodiversity). Given the complexity of the IBWT, many paths to partial or full completion of the project are possible. We evaluate two strategies for step-wise implementation of the 11 canals, based on economic or ecological considerations. We find that for each step in the project, the impacts on freshwater fish communities are sensitive to which canal is added to the network.Conclusions/SignificanceImportantly, ecological impacts can be reduced by associating the sequence in which canals are added to characteristics of the links, except for the case when all 11 canals are implemented simultaneously (at which point the sequence of canal addition is inconsequential). By identifying the fundamental relationship between the geometry of riverine networks and freshwater fish biodiversity, our results will aid in assessing impacts of IBWT projects and balancing ecosystem and societal demands for freshwater, even in cases where biodiversity data are limited.

The theory of stochastic differential equations driven by multiplicative Markovian dichotomous noise and a number of geomorphological relationships of river basins are used to investigate the geomorphological patterns of the width of riparian zones and the associated riparian vegetation biomass. Under the assumption that the scaling relationship between the river flow fluctuations, represented by the standard deviation of the flows, σQ, and drainage area holds, i.e., σQ ∼ As, we find that the scaling exponent s plays an important role in determining the patterns of the riparian width and vegetation biomass. In particular, high values of s, i.e., when the fluctuation grows relatively fast with drainage area, could result in the riparian zones of high‐magnitude streams being completely void of vegetation, whereas low values of s result in the riparian zones increasing in width with the stream magnitude. For very low s such an increasing trend of riparian width scales with the stream magnitude with an exponent approaching the negative value of the scaling exponent of the stream bank slope. The analysis presented here offers a potentially useful tool that can be used in watershed management, especially under changing climatic conditions, which may induce larger flow fluctuations and extreme events.