Composite indices have been widely used to rank the environmental performance of nations. Such environmental indices can be useful in communicating complex information as a single value and have the potential to generate political and media awareness of environmental issues. However, poorly constructed, or poorly communicated indices, can hinder efforts to identify environmental failings, and there are considerable differences in rank among existing environmental indices. Here, we provide a review of the conceptual frameworks and methodological choices used for existing environmental indices to enhance our understanding of their accuracy and applicability. In the present study, we review existing global indices according to their conceptual framework (objectives of the index and set of indicators included) and methodological choices made in their construction (e.g., weighting and aggregation). We examine how differences in conceptual frameworks and methodology may yield a more, or less, optimistic view of a country\'s environment. Our results indicate that (1) multidimensional environmental indices with indicators related to human health and welfare or policy are positively correlated; (2) environment-only indices are positively correlated with one another or are not correlated at all; (3) multidimensional indices and environment-only indices are negatively correlated with each other or are not correlated at all. This indicates that the conceptual frameworks and indicators included may influence a country\'s rank among different environmental indices. Our results highlight that, when choosing an existing environmental index-or developing a new one-it is important to assess whether the conceptual framework (and associated indicators) and methodological choices are appropriate for the phenomenon being measured and reported on. This is important because the inclusion of confounding indicators in environmental indices may provide a misleading view of the quality of a country\'s environment.

An index-based approach for a comprehensive evaluation of the potential risk for active substances and their mixtures to impact the environment was developed. Some of the indices considered already exist (PRISW-1, Priority Index), while others were created ex novo from indicators available on open-source platforms (PESTi, ECOi, AGROi). These indices maybe used for an evaluation before use of pesticides by farmers and advisers. The present approach was initially validated for herbicides in maize crops, but it can readily be applied to other PPPs and crops. PESTi index underline the physical and chemical characteristics as a whole, not considering the impact of other factors such as application rate or period of application. Hence, this index may underestimate the risk associated to a certain chemical. AGROi has a precautionary approach. The risk associated to a specific mixture derives from a combination of intrinsic characteristics of the chemicals, agronomic impacts, regulation restrictions and potential hazard to water compartment. The ECOi index is focused on the ecotoxicological impact against non-target organisms. The helpfulness of this index stands in its ability to easily discriminate the ecotoxicological impact of chemicals using indicators commonly available in literature and without making complex calculations. PRISW-1 Index discriminate active substances according to their risk against three representative non-target organisms. However, due to the intrinsic characteristics of each pesticide, a high PRISW-1 value could not always mean an easy movement of the chemical via runoff waters. The information deriving from Priority index may certainly help public authorities to select chemicals to be detected in water monitoring campaigns. The application of these indices may represent a valid decision tool for public stakeholders in defining agricultural measures to reduce the externalities of pest control.

Although several indices have been constructed and available at the Index database (IDB) for Sentinel-2 satellite to map and study several earth resources, no indices have been developed to map oil spill. We constructed band ratios (5 + 6)/7, (3 + 4)/2, (11+12)/8 and 3/2, (3 + 4)/2, (6 + 7)/5 using the high-resolution MSI (multi-spectral instrument) visible-near infrared-shortwave infrared spectral bands of Sentinel-2 by summing-up the bands representing the shoulders of absorption features as numerator and the band located nearest to the absorption feature as denominator to discriminate oil spill, and demonstrate the potential of this method to map the Wakashio oil spill which occurred in the Indian Ocean, off Mauritius. The resulted images discriminated the oil spill well. We also decorrelated the spectral bands 4, 3 and 2 by studying the spectral band absorptions and discriminated the spill as very thick, thick and thin. The results of decorrelation stretch method exhibited the distribution of types of oil spill in a different tone, distinctly. Both the image transformation methods (band ratios and decorrelation stretch methods) showed their capability to map oil spills, and these methods are recommended to use for similar spectral bands of other sensors to map oil spills.•This study demonstrated the application of band ratios and decorrelation stretch methods to map oil spill.•The methods discriminated the oil spill off Mauritius, and showed spill thicknesses from the Sentinel-2 data.•The new methods are recommended to use for the spectral bands of other sensors to map oil spill.