Spatially explicit population models are becoming increasingly useful tools for population ecologists, conservation biologists, and land managers. Models are spatially explicit when they combine a population simulator with a landscape map that describes the spatial distribution of landscape features. With this map, the locations of habitat patches, individuals, and other items of interest are explicitly incorporated into the model, and the effect of changing landscape features on population dynamics can be studied. In this paper we describe the structure of some spatially explicit models under development and provide examples of current and future research using these models. Spatially explicit models are important tools for investigating scale‐related questions in population ecology, especially the response of organisms to habitat change occurring at a variety of spatial and temporal scales. Simulation models that incorporate real‐world landscapes, as portrayed by landscape maps created with geographic information systems, are also proving to be crucial in the development of management strategies in response to regional land‐use and other global change processes. Spatially explicit population models will increase our ability to accurately model complex landscapes, and therefore should improve both basic ecological knowledge of landscape phenomena and applications of landscape ecology to conservation and management.

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This report documents Version 4.2 of InSTREAM, including its formulation, software, and application to research and management problems. InSTREAM is a simulation model designed to understand how stream and river salmonid populations respond to habitat alteration, including altered flow, temperature, and turbidity regimes and changes in channel morphology. The model represents individual fish at a daily time step, with population responses emerging from how individuals are affected by their habitat and by each other (especially, via competition for food). Key individual behaviors include habitat selection (movement to the best available foraging location), feeding and growth, mortality, and spawning. Fish growth depends on prey availability and hydraulic conditions. Mortality risks due to terrestrial predators, piscivorous fish, and extreme conditions are functions of habitat and fish variables. Field and analysis techniques for applying InSTREAM are based in part on extensive analysis of the model's sensitivities and uncertainties. The model's software provides graphical displays to observe fish behavior, detailed output files, and a tool to automate simulation experiments.

Many songbird populations in the midwestern United States are structured as a network of sources and sinks that are linked by dispersal. We used a modeling approach to examine explicitly how populations respond to incremental fragmentation of source habitat and how this response may vary depending upon two life-history attributes: fidelity to natal habitat ~ype and reproductive strength of the source. Fragmentation of source habitat led to a predictable decline in population for both attributes examined, but the manner in which populations declined varied depending upon the reproductive strength of the source and the level of fidelity. When the source was weak and produced few excess individuals, fragmentation of source habitats resuited in a predictable and parallel population decline of adults in both the source and the sink. In this situation high fidelity to natal habitats was important for maintenance of population size and structure. Low fidelity to weak sources resulted in population extinction; populations experienced a demographic cost by dispersing from high quality source habitat to low quality sink habitat. In contrast, when the source was strong and produced many excess individuals, fragmentation of the source led to population declines in both the source and the sink, but this decline was more abrupt in sink habitats. When the source was strong and produced a large excess of individuals, nonfidelity to natal habitats had little effect on metapopulation size and structure.Modelaci6n de los efectos de la fragmentaci6n del h~tbitat sobre la demografia de fuentes y sumideros en aves neomigratorias tropicales Resumen: Muchas poblaciones de aves cantoras en el medio-oeste de los Estados Unities estdn estructuradas come una red de fuentes ("sources") y sumideros ('sinks'), que se encuentran conectadas por medio de la dis-persi6n. En el presente estudio, usamos una aproximaci6n de modelaci6n para examinar explicitamente come las poblaciones responden al incremento en la fragmentaci6n a del hdbttat fuente y come ~sta respuesta puede variar dependiendo de dos atributos de la htstoria de vida: fidelidad al ripe de hcibitat native y fortaleza reproductiva. La fragmentaci6n del hdbitat fuente condujo a una declinact6n predectble en el tama~o poblacional para ambos atributos examinados, pero la manera en que las poblaciones decltnaron vart6 dependtendo de la fortaleza reproductiva de la fuente y el nivel de fideltdad. Cuando la fuente era ddbil, y producta un bajo nf~mero de individuos excedentes, la fragmentaci6n del hdbitat fuente result6 en una predecible y paralela producfa decltnaci6n poblacional de los adultos, tanto en la fuente come en el sumidero. En esta situaci6n, una alta fldeltdad a los hdbitats natives fue importante para mantener el tamaao y estructura poblactonaL La baja fidelidad a fuentes d(biles di6 come resultado la extinci6n poblacional, las 1397 poblaciones expertmentaron un alto costo demogrdflco al dtspersarse de los hdbitat fuente de gran caltdad a los h~bttat sumidero de baja caUdad. En ...

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure-without explicitly considering food webs-has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management.