Monitoring species abundance and distribution at the landscape scale.
Abstract
The abundance and distribution of a species are affected by processes which operate at multiple scales. Large-scale dynamics are increasingly recognized in conservation responses such as metapopulation management, transfrontier protected areas and softening the agricultural matrix. Landscape-scale monitoring is needed both to inform and judge their efficacy. In this Special Profile we address some of the challenges presented by monitoring at the landscape scale, how models of species distribution can be used to inform policy, and we discuss how monitoring at the global-scale could be approached. Collecting data over a large area is inherently costly, so methods which can provide robust information at low-cost are particularly valuable. We present two papers which test low-cost approaches against more data-hungry methods (indices of abundance vs. direct density estimates, and species distribution models built from presence-only vs. presence/absence data). Occupancy modelling is a useful approach for landscape-scale monitoring due to the relatively low-cost of collecting detection/non-detection data. We discuss challenges, such as non-random sampling locations and periodical unavailability for detection, in using detection/non-detection data for monitoring species distribution. Such data can also provide estimates of abundance and we show how existing models have been modified to allow the abundance of multiple species to be estimated simultaneously. Models of species distribution can be used to project likely future scenarios and thus inform conservation planning where distributions are likely to change because of climate change or changing disturbance patterns. We also discuss how an optimization framework can be used to make efficient management decisions for invasive species management in the light of imperfect information. Synthesis and applications. Monitoring is needed for many purposes including auditing past management decisions and informing future choices. Much monitoring data are collected at the site scale, although management authorities increasingly recognize landscape-scale dynamics. Recent global targets for conservation require monitoring which can report trends at the global-scale. Integrating data collected at a variety of scales to draw robust inference at the scale required is a challenge which deserves more attention from applied ecologists.