Settlement percolation: global maps of Critical Distances

TL;DR

This paper introduces a global method to measure settlement connectivity by identifying a critical distance at which settlements merge into a large cluster, providing new insights into urban and ecological spatial structures.

Contribution

It presents a novel percolation-based approach to quantify settlement configurations worldwide, offering a new metric for analyzing urban and land-use patterns.

Findings

Critical distance varies across regions and scales.

The GSP dataset enables new analyses of settlement connectivity.

Settlement clusters can be systematically characterized globally.

Abstract

A substantial share of the Earth's land surface is managed by humans, with cities representing the most extreme form of anthropogenic land use. There are zillion ways in which settlements can be arranged across a given area, and their specific spatial configuration has important consequences for both urban systems and the natural environment. Here, we introduce a novel approach to characterizing settlement configuration by systematically quantifying it in terms of a transition resembling percolation -- that is, by identifying the critical distance at which isolated settlements merge into a giant, overarching settlement cluster. We estimate this critical distance across multiple spatial scales and units, including national and subnational levels, non-overlapping tiles, and moving windows, covering the entire globe. The critical distance provides an independent measure of settlement connectivity and thus adds value to spatial analyses of settlement structure and its social, economic, and ecological impacts. Accordingly, our Global Settlement Percolation (GSP) dataset is relevant to a wide range of research communities, including those studying urban morphology, land-use patterns, and landscape ecology.