Ecological screening of climate exposure

Pareto screening

Each screen pairs one climniche exposure metric with one ecological criterion. A cell has Pareto rank 1 when no other retained cell is at least as preferred on both objectives and strictly preferred on one. Successive fronts describe increasing Pareto depth. The Pareto depth score rescales these fronts from zero to one, with one assigned to the non-dominated front.

The two objectives remain visible throughout the analysis. The result is a set of non-dominated alternatives rather than a weighted sum or a complete conservation ranking.

Mediterranean anchovy

The spatial fit is taken from the European anchovy example. Current SDM suitability provides the ecological criterion for both screens.

Positive Niche Distance Shift screen combines high current suitability with a larger positive Niche Distance Shift. Positive values represent movement away from the realised niche centre.

positive_shift <- climniche_priority(
  fit,
  exposure = "niche_distance_change",
  criterion_name = "Current SDM suitability",
  scope = "current",
  positive_only = TRUE,
  exposure_direction = "maximize"
)

Low Climatic Displacement screen combines high current suitability with lower Climatic Displacement. It identifies cells where higher suitability coincides with comparatively less local climatic change.

low_displacement <- climniche_priority(
  fit,
  exposure = "climate_change_amount",
  criterion_name = "Current SDM suitability",
  scope = "current",
  positive_only = FALSE,
  exposure_direction = "minimize"
)

Decision planes and maps

positive_shift_figure <- plot_climniche_priority(
  positive_shift,
  type = "both",
  map_value = "pareto_depth_score",
  study_region = mediterranean_boundary,
  degree_labels = "hemisphere"
)

low_displacement_figure <- plot_climniche_priority(
  low_displacement,
  type = "both",
  map_value = "pareto_depth_score",
  study_region = mediterranean_boundary,
  degree_labels = "hemisphere"
)

Panels (a) and (c) retain the two objectives and outline the first Pareto front. Panels (b) and (d) map the depth of each retained cell relative to its own screen. Pareto depth scores are therefore interpreted within a screen, not compared between the two maps.

Suitability is used here because it defines the current anchovy reference. A study can instead supply abundance, habitat condition, irreplaceability, restoration benefit or management cost through criterion, with the preferred direction set by criterion_direction.

The Pareto procedure follows the spatial multi-criteria application of Tracey et al. (2018). Lower Climatic Displacement indicates relative climatic stability in the fitted climatic space; it is not evidence of species persistence or a climate refugium.