Some ecological and environmental applications of Bayesian methods
by David Elston
Abstract: My use of Bayesian methods is motivated by the utility of MCMC to perform simulation-based inference to address the statistical issues raised by a range of ecological applications. I will describe some of these applications, and the generic issues that they raise. Examples will include the following. Firstly, a compositional analysis of streamwater on the basis of observations on chemical marker data, in which each pair of data items observed brings eight additional unknowns into the model. Secondly, a power calculation for a seabird monitoring scheme that allows for uncertainty in the estimates of parameters in the model of random variation, leading to the need to add an additional probability (the probability that the intended power is achieved) into the design specification. Thirdly, the analysis of both stock and change estimates of hedgerow lengths in the UK to provide annual estimates which can be used to assess evidence for whether change in hedgerow lengths is likely to be a principal driver for changes in population size of the yellowhammer, a farmland bird that has shown a marked decline in the UK over the last 30 years. Fourthly, an analysis of between-year variation in a common asymptotic growth curve model for length-at-date of sandeels fitted to data from two different sources, united by a model of selectivity, in which the focus of attention is on trends across years, particularly the extent to which the observed variation between years can be ascribed to environmental variables.
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