In a major report published Friday, the World Wildlife Fund (WWF) says that Earth’s wildlife populations have plummeted by about 25 percent overall since the 1970s, despite increased awareness about the importance of biodiversity.

In a Discovery News story, WWF director general James Leape says that all people will feel the impact of biodiversity loss because “reduced global diversity translates quite clearly into fewer new medicines, greater vulnerability to natural disasters and greater effects from global warming.”

Between 1970 and 2005, the WWF’s Living Planet Index — which tracks populations of nearly 1,500 vertebrate species — showed a decline of 27 percent. Human actions, including hunting, fishing, farming, pollution, and the expansion of urban centers, were cited as reasons for the decline.

Marine wildlife constituted the hardest-hit group. According to the WWF, marine wildlife populations declined by 28 percent since the ’70s. The most significant drop was recorded in the period since 1995.

You can explore one facet of this complicated story with NATURE’s “Mystery in Alaska,” which follows the startling disappearance of Steller’s sea lions from the Alaskan coastline. Follow the search for clues, as scientists and environmentalists race to find answers before the sea lions disappear for good.