One of the topics we discussed in science at Pathfinder this week was how one little act can create a chain-reaction. One example of this is when the people of Borneo got rid of malaria-carrying mosquitos using a man-made chemical. The chemical, DDT, killed not only the mosquitos, but also parasitic wasps that killed roof-eating caterpillars, and poisoned the geckos that ate the mosquitos, which, in turn, poisoned and killed the cats that eat the geckos. Consequently, the mice and rat population grew, spreading two new viruses. As a solution, cats had to be parachuted into Borneo. The domino affect story shows how one thing in this story, DDT, can lead to bigger things like the two new viruses.
Sea otters provide another example that shows that “everything is connected”, called a trophic cascade. A trophic cascade is when the addition or subtraction of a top predator causes big changes in the ecosystem. Sea otters play a vital role to keep sea urchins in check by eating them. Kelp forests that have sea otters are usually healthy, but kelp forests without healthy sea otter populations are unhealthy and are mostly now “urchin barrens” because too many urchins eat all of the kelp.
My last example is the African Elephant. In very big habitats, where they can migrate, elephants’ feeding habits create a balance between forest and savannah by taking down trees so other things can grow. But, in smaller ranges, because of habitat fragmentation, they can’t migrate and will completely devastate forested areas, leaving nothing but shrubbery.