Measuring habitat complexity and spatial heterogeneity in ecology

Abstract

Habitat complexity has been considered a key driver of biodiversity and other ecological phenomena for nearly a century. However, there is still no consensus over the definition of complexity or how to measure it. Up-to-date and clear guidance on measuring complexity is urgently needed, particularly given the rise of remote sensing and advent of technologies that allow environments to be scanned at unprecedented spatial extents and resolutions. Here we review how complexity is measured in ecology. We provide a framework for metrics of habitat complexity, and for the related concept of spatial heterogeneity. We focus on the two most commonly used complexity metrics in ecology: fractal dimension and rugosity.We discuss the pros and cons of these metrics using practical examples from our own empirical data and from simulations. Fractal dimension is particularly widely used, and we provide a critical examination of it drawing on research from other scientific fields. We also discuss informational metrics of complexity and their potential benefits. We chart a path forward for research on measuring habitat complexity by presenting, as a guide, sets of essential and desirable criteria that a metric of complexity should possess. Lastly, we discuss the applied significance of our review.

Review of the Effects of Enclosure Complexity and Design on the Behaviour and Physiology of Zoo Animals

“…The complexity of a habitat refers to its physical geometry, which includes abiotic components, such as its size, the density and arrangement of structural elements (rocks, waterways, soil, noise, lighting, etc.) and biotic components (e.g., the diversity of plant species and the structures created by them), and the presence of other individuals of the same or different species, for example [ 1 , 2 , 3 ]. The three-dimensional complexity created by the interaction of biotic and abiotic components is important because it generally allows for the maintenance of greater biodiversity [ 4 ].…”

“…Animals live in a physical world of three dimensions, a temporal dimension (i.e., time), and a social world. The physical world may be constituted of the biotic and abiotic environment, whereas time is purely abiotic and the social world is biotic [ 1 , 2 , 3 ]. It is the interaction between these three factors that create the animal’s world and gives it complexity.…”

“…; weight = 7800–9400 g) [ 9 ]. Perception of complexity is a function of being able to define scale with different levels of accuracy [ 3 ]. For example, if you measure the coastline of the U.K. with a measuring tape 1 metre long, this will provide you with a very different length from one that can measure in millimetres.…”

The jigsaw model: a biogeographic model that partitions habitat heterogeneity from area

“…The problem stems from an interaction between the mathematics of these models and the difficulty in meaningfully measuring habitat heterogeneity. There is no precise and accepted standard by which habitat heterogeneity should be measured (Panitsa et al 2006, Stein et al 2014, Stein and Kreft 2015, Triantis 2021, Loke and Chisholm 2022. Typically, habitat heterogeneity is measured either by counting the number of distinct communities ('biotopes') (Jüriado et al 2006, Panitsa et al 2006, or by measuring some number of abiotic environmental factors Ferree 2010, Shi et al 2010).…”

Understanding the role of microhabitats in intertidal rock pools to guide future eco-engineering designs

“…Habitat complexity, which refers to the different types, numbers and arrangements of structural elements in a given area (McCoy and Bell 1991;Tews et al 2004;Tokeshi and Arakaki 2012;Loke and Chisholm 2022), is an important driver of biodiversity (Pianka 2000;Loke and Todd 2016;Strain et al 2021). The prevalent hypothesis is that topographically complex habitats have a higher number of distinct resources and variations in environmental conditions, therefore allowing the coexistence of different species (Mac-Arthur and MacArthur 1961).…”