Kaze no Tani no Nausicaä, Kaijuu no Kodomo Recommendations
Both Nausicaa and Children of the Sea deal with concurrent themes of nature and environmental awareness, though Nausicaa focuses on a much larger scale and can be interpreted as more of an epic story or fantasy. Whereas Children of the Sea is somewhat more laden and, simultaneously, subtle with its metaphysical themes.
Children of the Sea and Nausicaä of the Valley of the Wind are both samples of great ecological storytelling, underlining the fact humanity is not separate from or above nature, but rather how it transcends our existence and achievements.
Of course, they have differences: Nausicaä is a high fantasy epic with a post-apocalyptic setting (with splendid worldbuilding), whereas Children of the Sea follows a more supernatural mystery-like approach that focuses on marine biology and inciting awe over the sea and the cosmos.