Improve your definition of, or enlarge your coverage of, environmental sciences
Currently the Nature Index has a category described as "earth and environmental sciences", but this is not really accurate: there are no environmental science journals included in this list.
I suggest you either add some journals (E.g. Environ. Sci. Technol. could be considered as, in my opinion, the most widely respected broad scope journal in its field), or change the category description to "earth sciences and ecology" to better reflect the coverage.