Keystone species

Written by Thary Gazi Goh
Photo by Goh Shang Ming

Fig is food for bats, squirrels and many other animals.

Keystone species are species that cause the entire ecosystem to fall apart if they are removed. 

We can imagine an ecosystem to be a network of connections between various species. Some species are more connected than others, and they can be the ones holding the entire network together.

Keystone species take their name from the keystone in stone bridges, this is the stone that holds the entire bridge structure together, and if removed causes the collapse of the entire bridge.

The biggest problem with keystone species is that we are rarely able to identify them without close study, and sometimes we only understand how they function when we see the results when they are gone.

A cautionary tale of disaster caused by removal of a keystone species is China’s “War on four Pests”. One of those pests was the sparrow, which sometimes ate the grain of farmers. 

A quarrel of Eurasian tree sparrow (Passer montanus) roaming at the edge of a fountain

Farmers were given quotas to kill sparrows, believing that this will increase their crop yields. What happened was a great ecological tragedy of the modern world.

Without sparrows to control them, the population of grasshoppers and other insects exploded. These insects started destroying crops and a massive famine followed.

This case really illustrates the folly of removing species from ecosystems. We often have no understanding of their functions and removing the wrong species can cause collapses of ecosystems with horrible consequences.

This is one of the reasons why we have to try to protect as much of our native ecosystems as possible. We sometimes do not know what a keystone species is until it is too late.