IN THE environment, there is a symbiotic relationship among living things. If one species is eliminated, the others who depend on it will be affected as well. For instance, flowers depend on bees for pollination. In the food chain, the predator-prey relationship keeps a healthy balance on the population of species.

The ecologist Robert Treat Paine made experiment by removing the ochre starfish (Pisaster ochraceus) from a seashore in Washington State in the United States. The absence of the predator had a dramatic effect on its ecosystem. In less than a year, a diverse tidal environment collapsed into a monoculture of mussels because the starfish was no longer around to eat them. By keeping mussel numbers down, the starfish had allowed many other species to thrive, from seaweed to sponges.

For some species, the interconnectivity is not obvious. For instance, how will the decline in a large animal like elephants cause the decline of a tiny species like termites? A study by ecologist Amy Dunham and graduate student Therese Lamperty, published in Biological Conservation, reported that in African rainforests where large animals are hunted, the abundance of termites falls by 170 times.

Termites, which are considered pests in our homes, are actually a critical component of the rainforest. They are one of the planet’s best recyclers. They are important ecosystem engineers responsible for plant decomposition, carbon flux and the physical properties of the soil, and serve as a key food resource for other species.

So how are elephants and termites connected? According to the researcher, when megafauna like elephants are removed from the environment, termites lose both deadwood from trampled brush and their dung as nutrients. They said that when you have large animals like elephants that have disappeared from a forest, you’re likely to have some cascading impacts, and these small things that run the world, the insects, are likely to be affected.

The study also found that where elephants and other megafauna disappear, the forest floor becomes dense with vegetation, providing a platform for increased numbers of web-building spiders. These in turn eat such flying insects as pollinators and are themselves a food source for insectivorous birds. That may also have consequences for the ecosystem that require further scientific study.

Some of the problems we have today may have been caused by the upset in the ecosystem. We have a dengue outbreak because of the surge in the population of mosquitoes, which may have been caused by the decline in the population of dragonflies, bats, small fish and other predators.

The imbalance in the ecosystem eventually affects us humans.