Discarded Christmas trees, a gift to Stockholm's fish

On a freezing January morning, dozens of discarded Christmas trees collected after the holidays are tossed into Stockholm's glacial waters, recycled to provide a welcoming habitat for marine life.

How bringing back lost species revives ecosystems

Scientists often study the grim impacts of losing wildlife to hunting, habitat destruction and climate change. But what happens when endangered animals are brought back from the brink?

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