Convergence of Global Change Issues

Convergence of Evidence

Issue impact (km2)

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Convergence of evidence: where the evidence leads

The occurrence of multiple global change issues (GCIs) at a location suggests a potential for land degradation (at least in some form)

The map illustrates the concept of convergence of evidence. It depicts where global change issues (GCIs) relevant to land degradation coincide at a global scale. The map is constructed using two basic kinds of global data: land cover/land use and global change issues (GCIs):
First, land cover/land use data: Total global land mass is stratified into broad classes based on their share of cropland, rangeland, and forest (the term ‘forest’ is used to indicate the ‘tree cover extent’ mapped in the dataset). Depending on specific interests, the availability of data, region and scale of investigation, other stratifications, e.g. climate, soil, and ecosystem services, could be used.
Second, global change issues: 14 global change issues (GCIs) were selected. These GCIs are a mixture of biophysical and socio-economic drivers, and were selected because of their availability as global data and their usefulness as factors associated with land degradation. Based on whether its value at a particular spatial location is above or below a certain threshold, each GCI is classified as being either a concern for land degradation (e.g. declining productivity) or not (e.g. stable productivity).
A GCI threshold is calculated based on the per class distribution of the dataset within each of the broad land classes. At this global scale, for most GCIs the median value is considered (except for agriculture input and land productivity - see table on GCIs for details).
The global map shown here does not represent land degradation. Rather, it illustrates the convergence of evidence of GCIs relevant to land degradation. As noted previously, the correct interpretation of the map must consider contextual information on regional and local conditions, as per individual user’s knowledge. See text for details and following pages for theme maps that illustrate possible stakeholder’s interests.

Case study:

The six most frequent combinations of 9 coinciding GCIs.
There are 13 327 different combinations of the 14 GCIs behind the map above. Some cover large areas, other just a few pixels. The table presents the 6 most frequent combinations of 9 GCIs.
Source: WAD3-JRC, 2018.