SDG #14 is to “Conserve and sustainably use the oceans, seas and marine resources for sustainable development.”
Within SDG #14 are 10 targets, of which we here focus on Target 14.1:
By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution
Target 14.1 has one indicator:
Indicator 14.1.1: (a) Index of coastal eutrophication; and (b) plastic debris density
Eutrophication occurs due to excess nutrients - such as nitrogen and phosphorus - in a water body. To measure this, as the first part of the indicator, we can measure the levels of the chlorophyll-a, the key to photosynthesis in green plants and algae. The concentration of chlorophyll-a acts as a proxy for eutrophication, as too many nutrients in a water body can result in algal blooms. These blooms are signs of life in the form of algae. But eutrophic environments suck out the oxygen from the water, depriving other lifeforms which call it home.
The measure is how much chlorophyll-a is on the coast for each country varies from the global average. The countries with the highest levels in 2022 were:
Canada
Russia
Bulgaria
Sri Lanka
the Congo’s
Cameroon
Gabon
the Guiana’s.
As of 2020, the world’s laggards in plastic debris density were:
Ghana
Cameroon
Malawi
Cyprus
Georgia
Each of the above countries had greater than 10 million items of plastic per square kilometre on their shores. We should also keep in mind a couple dozen countries with coasts didn't have 2020 data for this measure.
The global average is 4.2 million bits of plastic per square kilometre of beach. This is a reduction from the baseline at the start of the SDG period in 2015 of 31 million per square kilometre, following a rise in 2018 up to 35 million.
