Are ecologists conducting research at the optimal scale?

Abstract

AimThe spatial extent (scale) at which landscape attributes are measured has a strong impact on inferred species-landscape relationships. Consequently, researchers commonly measure landscape variables at multiple scales to select one scale (the 'scale of effect') that yields the strongest species-landscape relationship. Scales of effect observed in multiscale studies may not be true scales of effect if scales are arbitrarily selected and/or are too narrow in range. Miscalculation of the scale of effect may explain why the theoretical relationship between scale of effect and species traits, e.g. dispersal distance, is not empirically well supported.Location World-wide.Methods Using data from 583 species in 71 studies we conducted a quantitative review of multiscale studies to evaluate whether research has been conducted at the true scale of effect.Results Multiple lines of evidence indicated that multiscale studies are often conducted at suboptimal scales. We did not find convincing evidence of a relationship between observed scale of effect and any of 29 species traits. Instead, observed scales of effect were strongly positively predicted by the smallest and largest scales evaluated by researchers. Only 29% of studies reported biological reasons for the scales evaluated. Scales tended to be narrow in range (the mean range is 0.9 orders of magnitude) and few (the mean number of scales evaluated is four). Many species (44%) had observed scales of effect equal to the smallest or largest scale evaluated, suggesting a better scale was outside that range. Increasing the range of scales evaluated decreased the proportion of species with scales of effect equal to the smallest or largest scale evaluated. Main conclusionsTo ensure that species-landscape relationships are well estimated, we recommend that the scales at which landscape variables are measured range widely, from the size of a single territory to well above the average dispersal distance.

Recent Progress on Spatial and Thematic Resolution in Landscape Ecology

“…Another common multi-scale analysis method used frequently in landscape ecology characterises multiscale species-environment relationships by altering the size of circular buffers/kernel around point locations at which ecological data is sampled [61][62][63], while leaving the spatial or thematic resolution constant. However, this type of multi-scale analysis is not an explicit focus of this paper as it does not involve altering the spatial and/or thematic resolution to identify scale effects (see [63,64] for a comprehensive review).…”

A Bayesian method for assessing multi-scale species-habitat relationships

“…Despite an awareness of the issues associated with spatial scale mismatches in ecology (Horne and Schneider 1995;Chalfoun and Martin 2007;Hurlbert and Jetz 2007), identifying, incorporating, and quantifying influential processes at various scales in ecological modeling has proven difficult and is often ignored or over-simplified (Wheatley and Johnson 2009;Jackson and Fahrig 2015). Although there is presumably not a single 'best' spatial scale at which to associate species and their habitats for all species or ecological conditions, it is possible to reveal relevant ecological associations when the scale of analysis approaches the operational scale of the process of interest.…”

Modelling seasonal habitat suitability and connectivity for feral pigs in northern Australia: towards risk-based management of infectious animal diseases with wildlife hosts

“…Addicott et al (1987) argued that each ecological process has its own unique ecological neighbourhood and the choice of process will determine the appropriate timeframe and scale of measurement. Yackulic & Ginsberg (2016) provided an excellent synthesis of how a species' biological and behavioural levels can be linked with ecological processes and suitable grains and extents of analysis to explain distributional patterns consistent with the metapopulation perspective on mobile species adopted here (Fig 2.1 have been devoted to finding the "right" ecological neighbourhood at each of these biological levels (Section 2.4.3;Holland et al 2004;Jackson & Fahrig 2015;McGarigal et al 2016). When studying habitat suitability for local feral pig subpopulations (research question 2), I…”

“…'Scale-optimized' variables that best explain a given response were then selected and relationships between them modelled in environmental space (Holland et al 2004;Jackson & Fahrig 2015;McGarigal et al 2016;Miguet et al 2016). In resource selection functions, for example, multiple scales effectively constrained the area in which resource availability was measured and subsequently contrasted with actual use (DeCesare et al 2012;Martin & Fahrig 2012;Laforge et al 2016;Paton & Matthiopoulos 2016).…”