I echo Aran. It would be the scientists saying that these targets are necessary to sustain the ecosystems on which human and natural life depends.
Oceans provide climate regulation, the oxygen we breath, food and food security. They are a source of wonder, culture, and spiritual strength. Also, of course, you've got to include in your message the importance of a healthy ocean for ocean-dependent economies. A UBC fisheries economic research unit calculated the value of industries on the north coast that depend on a healthy ocean and came up with over $1 billion of revenue being generated annually from industries that rely on a healthy ocean. That definitely has to be part of the message as well.