B. Halpern and colleagues developed this indicator by integrating 12 global datasets of anthropogenic drivers available data the 2008 and 19 global anthropogenic stressors for 2013 (Table 1) on ecological change for 20 marine ecosystems (Table 2) at a 1 km² resolution (Halpern et al. 2008; Halpern et al. 2015). The anthropogenic stressor datasets were rescaled to range from 0 to 1 and used to derive pressure data by adjusting for habitat pressure and vulnerability. The sum of the pressure data was then calculated to create the cumulative impact datasets for each year the indicator was measured. Of the original 19 anthropogenic stressors used to develop the latest 2013 dataset, a subset of the 12 stressors used to derive the 2008 dataset were used to develop a comparable 2013 human impact dataset. Halpern and colleagues developed the change in the Cumulative Human Impacts on Marine Ecosystems by calculating the difference between the 2008 and 2013 (subset) pressure and cumulative impacts.

Table 1. Anthropogenic stressors included in the datasets used for the 2013 baseline and change between 2008-2013 for the Cumulative Human Impacts on Marine Ecosystems indicator (adapted from Halpern et al. 2015 Supplementary Table 1). 

* Stressors only available for the baseline 2013 dataset. These stressors were not used to measure human impacts for the 2008 dataset, and therefore were not used in the subset 2013 dataset compared to the 2008 to calculate change.

Table 2. Marine ecosystems considered in the datasets used for the 2013 baseline and change between 2008-2013 for the Cumulative Human Impacts on Marine Ecosystems indicator (adapted from Halpern et al. 2015 Supplementary Table 1).