New complexity discovered in ecosystems

Todd Palmer, ecologist, University of Florida, has discovered a new complexity in nature. Giraffes in Kenya feed on thorny acacia trees, so protecting the trees from giraffes, elephants, and other herbivores should help acacias to grow better, right? Wrong. Acacias and a species of ants live together in a mutually beneficial arrangement. The ants nest in the acacia's thorns and feed on nectar produced by the thorns. They also swarm out and attack giraffes and elephants when they start feeding on the acacia. But that's not the end of the story. If you protect the acacias from herbivores, the acacias grow fewer thorns and produce less nectar within a year or two. Then the ants become lazy and drop their guard, leaving the acacia vulnerable to invasion from a third actor -- wood-boring beetles. Soon their tunnels have the tree sickly, dying, or dead.

Similar complex interactions have been observed when wolfs are killed (elk expand killing off aspen) and when sharks are killed (populations of small algae-eating fish balloon and without the algae, corals die). The moral of the story: we humans have a lot to learn about Nature before we can tinker safely with its complex feedback systems.