““The nitrogen cycle is a kind of miracle. The nitrogen cycle requires bears. Brown bears catch salmon in streams and rivers. Then the brown bears carry the salmon farther inland, and they bury these nitrogen-rich fish in the ground for later retrieval. But bears have short memories, and often they forget the fish where they left them, far inland from the streams. And the fish bodies decompose, leaving a reservoir of nitrogen in the ground. This creates a rich and fertile environment for large trees to grow, and in fact without the nitrogen deposited by the bears, very large old-growth trees would probably never have been able to continue their growth cycle. Five hundred years ago, if someone had removed all bears, none of the old-growth trees we have now would have grown.””
