What is “scale” and why is it so important to consider when doing geographical research?

Scale is a concept that have different meanings to different people. A cartographer most likely thinks scale refers to the scale of a map, i.e. the distance that one unit on the map represents in the real world. But scale doesn’t always refer to distances. It can be hierarchical and this refer to different levels of administration, or even temporal. Gibson et al (2000) define scale as the “spatial, temporal, quantitative, or analytical dimensions used to measure and study any phenomenon”.

For example, if you are trying to understand how climate or environmental change may affect migration, you can analyze this relationship at a multitude of levels, in several different dimensions. You may compare different migration patterns with environmental factors between countries, districts, municipalities, and even villages. Similarly you may be interested in linking environmental changes to migration events over the course of 1000, 100, or 10 years, looking at 5-year periods, individual years or even months.

Scale as a tool for outlining these levels and dimensions includes two important parameters, the extent (i.e. the area or time covered) and the resolution (i.e. the smallest unit of analysis). Often researchers decide on the spatial extent they want for their study, referring to their study area. But then they also need to define their resolution, which is often determined by default, based on the available data. Both extent and resolution of the temporal and spatial dimensions are highly influencing the way we see relationships and the strength of statistical relationships, which mean that it can lead to results that aren’t really stable, that would change if you changed the analytical dimensions.

I encourage all researchers to consider scale and how it may affect their results and conclusions, especially when working on interdisciplinary research combining population and environment factors, where data is most often not harmonized. More information can be found in our recent open access publication Data and methods in the environment-migration nexus: a scale perspective, which is part of a special issue on Climate and Migration.