Many dynamical systems such as ecosystems exhibit non-linear responses to changes in their external drivers, resulting in possible wide state shifts with strong ecological or economical consequences. This often happens when a system exhibit a change in its stability properties as a threshold is crossed, e.g. going from multiple stable states to a single stable state. For a few decades, much research has been dedicated to finding a way to anticipate these tipping points in ecological systems. This has led to the suggestion of several indicators that could reflect the proximity of an ecosystem to a tipping point.
This package implements the computation of these indicators, or early-warning signals (EWS), on spatial raster data. High-level functions and methods provide familar workflows to compute the indicators and display their variations along environmental gradients or time-series. Lower-level functions are also available to integrate early-warning signals in a different workflow.
Main functions provided by this package
"Workflow" functions:
generic_spews
: Generic spatial EWS
spectral_spews
: Spectrum-based EWS
patchdistr_spews
: EWS based on patch-size distributions
Individual indicators:
indicator_moran
: lag-1 spatial autocorrelation (Moran's I)
indicator_variance
: Spatial variance
indicator_skewness
: Spatial skewness
indicator_sdr
: Spectral density ratio (SDR)
indicator_psdtype
: Patch-size distribution shape
indicator_plrange
: Power-law range
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