An arch looks strong. Yet its strength is completely dependent on the keystone that rests in the middle. Remove this keystone and the arch will collapse immediately. Likewise, in the natural environment, there are certain species that perform functions very similar to the keystone that we find in an arch. As such, the keystone species are as important as they are unique.
The role of keystone species can be imagined as a sort of eco-system glue, subtlety binding and teasing the environment together in a stable and sustainable harmony. Now, let’s look at five species that perform this sticky and all important role.
North Pacific Sea Otters
The kelp forests in the shallows of the North Pacific play a vital role in their waters, providing good shelter and a habitat for many small aquatic species. But kelp forests are under threat from one seriously sharp annoyance. Sea urchins feed on the roots of kelp and easily remove it from the ecosystem. Thankfully, sea otters are a reliable keystone predator that feed on sea urchins and therefore help the kelp forests survive. The sea otters are small in number, but effective in neutralising the threat coming from those lonely, globular, sea urchin fiends.
In the 18th and 19th centuries, sea otters were hunted by fur traders wanting to make a quick buck and fisherman who thought the otters were eating the fish they were trying to catch. As a result, they were hunted nearly to extinction. But in 1911, the International Fur Seal Treaty was agreed, which made hunting sea otters an illegal activity. Thankfully, the sea otter population has been restored, the kelp forests now thrive and the marine environment is protected.
Keystone species are typically small in numbers and biomass. But these Antarctic krill go strongly against the norm. Despite their size, never being more than 6 centimetres long or over 2 grams in weight, these shrimp-like creatures can swim in swarms of up to 30,000 strong and are the largest single-species biomass in the Antarctic Southern Ocean! Whales, penguins, albatrosses, seals and many of the Antarctic fish population feed almost exclusively on them, making krill one of the most indispensable of keystone species.
The importance of Antarctic krill to this eco-system means that, despite their abundance, any fishing activity must be monitored very closely. With the popularity of krill oil and other krill-based products increasing, fisheries and environmental groups alike are at pains to ensure that krill harvesting is done in a sustainable fashion.
The elephants of the Savanna are keystone engineers that have played an important role by indirectly altering the landscape around them. The elephants’ love of uprooting trees and undergrowth has dramatically changed the environment of the Savanna, from what was once dense forest to what is now open grassland. Peacefully coexisting with other animals, the activity of Savanna elephants has created a whole new environment which other species depend upon.
Unfortunately, though, it’s no longer clear cut who the engineers of the Savanna really are. That credit may now go to African poachers that have killed off much of the elephant population in the area. Although laws have been put in place to stop such activity, it has proved hard to monitor over such an expansive area. Africa’s biodiversity depends on these elephants; we can only hope that things will change soon.
The Acorn Banksia is a shrub of Western Australia. It is a keystone mutualist, taking part in interactions mutually beneficial to the things around it. The Acorn Banksia certainly doesn’t look like much, but all of the honeyeaters rely on it for its nectar. Western Australia reaches a critical period each year when other plants cannot produce nectar.
The only thing that does is the Acorn Banksia. Without the Acorn Banksia, the 365-day chain of nectar is broken. The honeyeaters are lost. And it snowballs. Because, if you lose the honeyeaters, you lose a huge proportion of the plant population that rely on them for pollination. This little orange shrub is worth its weight in gold.
Central and South American Jaguar
Our last example is the jaguar, another type of keystone predator. Like the sea otter, the jaguar performs the important task of stabilising the environment around it through the hunting of other species. And these jaguars are particularly special. As apex predators with a ferocious bite, the jaguar has a wide and varied diet allowing it to consume a staggering 87 different species of prey! This figure alone embodies its keystone status as an animal small in number with a disproportionate effect on its environment.
Considered “near threatened” by conservationists, again the jaguar falls prey to a familiar species: Homo sapiens. Deforestation has destroyed the jaguars’ natural habitat and poaching claims 15,000 jaguar skins each year – a crying shame for such a beautiful and powerful keystone species.
There we have it. Hopefully this has shown you how important keystone species are for the stability of the environments they help to maintain. But some of these examples have also shown how keystone species are eliminated by something far more dominant: us. We have mastered the environment and, as a result, now dominate it. We are the keystone engineers now, and we need to look at the consequences of our actions and take responsibility.
Gary Bale writes on environmental issues and conservation. He has a particular interest in sustainability.