Modeling landscape functions and effects: a network approach

Landscape functions, including sediment and nutrient trapping, pollutant degradation, and flood control, are often adversely affected by human activities. Tools are needed for assessing the effects of human activities at the landscape scale. An approach is presented that addresses this goal. Spatially-explicit ecosystem units and their connections are used to define a transport network. A linear transport model is a tractable approach to landscape analysis for assessment purposes. The ability of each unit to provide ecosystem goods and services is considered explicitly in terms of its place in the network. Based on this simple model, landscape-level effects of impacts to the functioning of a given ecosystem unit can be calculated. Effects of changes in network structure (due to changes in the flow regime) can also be assessed. The model allows several useful concepts to be defined, including change in buffer capacity, free capacity, an ordinal ranking of the relative importance of ecosystem units to overall landscape functioning, and differentiation of cumulative versus synergistic effects. Utility functions for valuation of landscape function are also defined. The framework developed here should provide a foundation for the development of analytic tools that can be applied to assessment and permitting activities.