Population-level mechanisms for reddened spectra in ecological time series

The temporal variability of many animal populations increases with the length of census period. This pattern is associated with the reddened spectral colour, quantified by the spectral exponent, which is typically around + 1. We used simulation models to explore the effects of various population-level processes on the spectral colour of the simulated time series of abundances. Our results showed that the observed spectral exponents could be explained as the effect of a combination of measurement error and natural variability (in the form of white environmental noise). Thus, it may not be necessary to invoke complex varieties of environmental noise to explain the observed spectral exponents.