Intensity Analysis to communicate land change during three time intervals in two regions of Quanzhou City, China

Article

Abstract

Intensity Analysis is a mathematical framework to express differences within a set of categories that exist at multiple time points. The original version of Intensity Analysis communicated land change in one region during time intervals that have various durations. Our new manuscript modifies Intensity Analysis’ equations and graphics to compare various regions during time intervals that have the same duration. This manuscript also combines Intensity Analysis with a method to express change as the sum of three components: quantity, exchange, and shift. We give two new insights concerning interpretation, which apply also to the original version of Intensity Analysis. First, we quantify the proportion of each change that is attributable to the start size of the category versus the deviation from a uniform intensity. Second, we clarify that a category’s gain intensity expresses the percentage of the category’s end size that derives from the gain during the time interval, while a category’s uniform transition intensity indicates the aggressiveness of the category’s gain. We illustrate the approach by comparing the Inland versus the Coastal regions of Quanzhou City, China. Inputs are GIS maps at 1995, 2000, 2005, and 2010 that show six land categories: Built, Cultivated, Forest, Garden, Unused, and Water. Change as a percentage of the Coastal region is greater than change as a percentage of the Inland region during each time interval. Exchange between categories is the largest component of change in each region during each interval. Cultivated loses and Built gains more intensively than the uniform change intensity in each region during each time interval. Built’s gain targets Cultivated intensively in each region during each interval. Built’s targeting explains most of the transition from Cultivated to Built in the Inland region, while Cultivated’s size explains most of the transition from Cultivated to Built in the Coastal region. If the data are sufficiently accurate, then these results strengthen the concern for the transition from Cultivated to Built, as the loss of Cultivated land threatens food security in China. Scientists can apply Intensity Analysis by using free software available at www.clarku.edu/~rpontius.

Publication Title

GIScience and Remote Sensing

2020

57

1

21

36

1548-1603

DOI

10.1080/15481603.2019.1658420

Keywords

China, GIS, intensity analysis, land change, Quanzhou City, region

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