Beyond fragmentation: the continuum model for fauna research and conservation in human-modified landscapes

Animal distribution patterns in human-modified landscapes are often examined from the basis of the "fragmentation model", which recognises habitat patches located within an inhospitable matrix. The fragmentation model can establish correlations between landscape pattern and animal distribution patterns. However, it is limited in its ability to generate a process-based understanding of species distribution patterns. Here we propose a process-based conceptual landscape model. The "continuum model" is derived from continuum theory, and recognises the importance of space-related ecological variables alongside other factors, such as the availability of suitable food, shelter, and climatic conditions. The continuum model allows for gradual changes in these variables through space, and assumes species respond individualistically to their environment. We contrast the continuum model with the fragmentation model, and outline how it can be used to interpret and design empirical studies. While the fragmentation model may provide a satisfactory description of ecological patterns where many species are confined to human-defined "patches", the continuum model can help to establish links between fundamental ecological processes and individualistic species distribution patterns. Conservation guidelines arising from the fragmentation model will emphasise the importance of large and well-connected pre-defined "habitat" patches. Conversely, the continuum model recognises potentially large discrepancies between different species' ecological requirements. Conservation guidelines arising from the continuum model therefore will focus on habitat heterogeneity at multiple spatial scales to enhance the number of niches available to different species.