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The natural world is an intricately interconnected web of life, and keystone species play a critical role in maintaining its balance and health. From majestic elephants to humble moss, these species act as linchpins, holding together the ecosystem and preventing it from falling apart.
The loss of a keystone species can have far-reaching and devastating consequences for other species. By understanding the importance of these species, we can better appreciate the intricate and fragile nature of our planet’s ecosystems.
What is a Keystone Species?
In the simplest sense, a keystone species is a species that holds the balance within an ecosystem; they act as the keystone, keeping all other stones in place.
If these species were to be removed from the ecosystem, there would be a rise in the population of other species on which they prey, throwing things out of balance.
When most people think about a keystone species, they imagine a predator. It’s true that a lot of keystone species are at the top of the food chain. In fact, it was a predatory species; the sea star, that was the inspiration for the notion of keystone species in the first place.
In 1969, an ecologist named Robert Paine removed sea stars from a particular area only to find that the mussel populations, on which they preyed, blew up out of control. In turn, this caused the complete wipe out of other species, like flowering sea anemones which taught Paine the importance of the sea star in this environment.
Often described as having a disproportionately large effect on their community, keystone species have the ability to control the population of other species within the ecosystem.
Types of Keystone Species
Predators are often thought of as the main keystone species, but there are other types. These species play an important role in protecting their ecosystem from either going extinct or becoming overpopulated.
Back in the 1920’s, gray wolves were almost hunted to extinction in the Yellowstone National Park. As a result of this, prey species in the area became incredibly abundant. This demonstrates the need for predatory keystone species as they help to control the numbers of prey species within their ecosystem.
Some of the top predators, like sea otters, wolves, and lions are critical in ensuring controlled populations of small carnivores and herbivores, meaning that the structure of the ecosystem remains intact. Without them, the ecosystem would be at risk of trophic collapse, where the lower levels of the trophic system are negatively affected by the removal of the highest level.
This takes us back to the wolves in Yellowstone which were not replaced until the mid 90s. However, when they were replaced, we saw new effects, which included increased vegetation and a better abundance of beavers.
While predators are some of the most common keystone species, ecosystem engineers are just as important. These creatures do not affect the ecosystem through their diet but by modifying or maintaining the environment or even creating new aspects of it.
Elephants and earthworms are among some of the most notable keystone ecosystem engineers, but let’s use the beaver as an example. These animals build dams that divert the natural flow of water, in turn creating wetland areas. What’s more, they’ll often take dead wood from trees, which encourages new tree growth, therefore allowing the ecosystem to continue thriving.
Mutualists are organisms that form a mutually beneficial relationship with other organisms. This pairing is also essential to the survival of the ecosystem. A great example of this is bees and flowers. The flowers benefit because the bees spread their pollen which in turn allows them to reproduce while the pollen is used by the bees for food, ensuring their survival.
Not only this, but these mutualistic relationships help to maintain balance within the ecosystem and this supports the survival of other species that live there.
Importance of Keystone Species
Without keystone species, we would see the collapse of many ecosystems and this could have a wider knock-on effect. With that in mind, let’s take a look at the important role these species play.
Helps Maintain Biodiversity
Biodiversity within any ecosystem is essential as a support system for all life and keystone species play an important role in maintaining this. In fact, one could argue that they were solely responsible for retaining a balance in local diversity.
Without keystone species, any given population could blow up which would in turn lead to the extinction of another, vastly reducing biodiversity within the area.
Help to Regulate Species Populations
If one species were to explode, there would be a significant risk that they would monopolize all of the resources within that area, putting other species at risk. But keystone species help to maintain the balance. While you might not think that’s such a big deal, consider that any imbalance could have a direct effect on humans.
All animals and plants need the right habitat to survive and some keystone species are responsible for creating this. Think about the beavers, building their dams, and creating wetland habitats for a variety of life.
Elephants will migrate and trample down grasslands which in turn supports the growth of smaller species.
For any living thing to survive in an ecosystem, the soil must be fertile and there must be a high-quality water source. One of the important roles of keystone species is to maintain both of these things through nutrient cycling. An essential process known as nitrification is imperative to plant life yet can only be carried out by microorganisms that are considered to be a keystone species.
Another obvious example of nutrient cycling is that of the Arctic fox which, by denning, has a direct impact on the abundance of plant life due to an increased nitrogen level within the soil.
Examples of Keystone Species
There are keystone species in all ecosystems, and they come in all shapes and sizes.
Elephants on the African savanna act as ecosystem engineers. Without them, the savanna would be more of a forest than the grassland it is and this would mean that grazing animals such as antelope would not have adequate feeding grounds.
These huge mammals knock down trees in order to get to the leaves for food which is what keeps tree growth in check.
And it isn’t just the grazing animals that benefit from this. Without elephants to keep the grasslands maintained, smaller mammals like mice would have no dry soil in which to burrow. What’s more, this abundance of life on the savanna serves as prey for the apex predators here, such as lions and hyenas.
In the rainforests, jaguars are unfortunately a near-threatened species, but their survival is imperative to the overall health of the ecosystem. Fragmentation is one of the biggest problems for this species as well as persecution. Sadly, while there are protective measures in place, farmers will still shoot on sight if they see these big cats on their land.
But without jaguars, the population of many prey species would get out of hand. These are important predators that not only control population numbers, but also ensure survival of the fittest. For example, jaguars lie in wait and strike their prey; those that are stronger are more likely to get away and, when they reproduce, their offspring are more likely to be stronger as well.
Many of the jaguar’s prey are herbivores, so it’s essential for there to be good control because an explosion of these species would deplete local vegetation.
3. Honey Bees
Bees are among some of the most important pollinators on the planet and are known to pollinate up to 70% of human crops. However, many species including the bumble bee are under threat due to things like habitat loss and climate change.
Honey bees are essential to any ecosystem they inhabit, and they’re found all over the world apart from Antarctica.
Without them, many species of plants would die off since bees are responsible for pollinating their flowers and aiding in plant reproduction. In fact, it’s thought that around 50% of plant species would become extinct if we were to lose the honey bee. Moreover, many other animals like insects and birds would not have access to plants that they use for food.
The world’s coral reefs are in serious decline from things like coral bleaching and global warming. In order to maintain these essential habitats we have to rely on the beautiful parrotfish.
One of the things that pose a threat to the reefs is a build-up of algae which can be incredibly invasive, at times killing the reef entirely. However, parrotfish feed on these algae, keeping them in check and ensuring the health of the reef.
5. Gray Wolves
With the extinction of the gray wolf in the Yellowstone National Park, a trophic cascade quickly occurred, affecting numerous other species. This happened over a century ago, and the wolves were only reintroduced to the area in the 1990s.
The collapse of the ecosystem was not only felt in the Yellowstone National Park, but also across all of North America. You see, wolves are apex predators, and without them, there was a serious explosion of their prey species, which led to competition for resources right down to the grass on the ground.
Even their reintroduction caused another trophic cascade, and things took some time to get back into balance. However, this event gave scientists the chance to get a good look at the importance of predatory keystone species.
When you think of a beaver, I’d imagine that you would think of the dams that they build and these are what makes them a keystone species. But these dams are not mindlessly thrown together, beavers are among some of the most impressive ecosystem engineers in the world, and the intricacies of their construction are not to be sniffed at.
For starters, carbon and nutrients are trapped within the area of the dam meaning that the quality of the water further downstream is improved. Moreover, dams slow the flow of the water meaning a lesser risk of flooding.
Not only this, but the dams themselves create habitats for a plethora of creatures ensuring biodiversity. Animals like the salmon are known to grow bigger and stronger in areas where there are beavers since these aquatic mammals do not eat fish and so populations can thrive.
And if all that wasn’t enough, beavers use materials from old trees such as dead bark and wood. This serves as a kind of maintenance, ensuring future growth and stability of the landscape.
7. Prairie Dogs
Prairie dogs are perhaps one of the most diverse keystone species I’m going to talk about as they protect their ecosystem in a variety of different ways. In fact, if these animals were taken out of their environment, it would be almost certain that the ecosystem would collapse.
These animals are known for their intricate underground tunnel systems that provide protection from predators. In fact, being a food source for predators is one of the things that makes prairie dogs an important keystone species. However, their tunnels also serve as shelter and protection for many other species. For example, the tunnels are essential for the survival of species like the rattlesnake during their brumation period.
On top of this, the prairie dog helps to maintain the growth quality of local grasses by clipping them back. This ensures good quality resources for all others in the environment.
8. Grizzly Bears
The grizzly bear is not only a keystone species but also a bioindicator which tells us a lot about the state of an ecosystem. This is due to their ability to thrive in many different habitats which they also help to remain balanced.
In terms of their role as a keystone species, grizzly bears have long been in competition with the gray wolf as both species go after the same prey. Of course, the gray wolf was missing from much of North America until the last few decades after it was reintroduced.
One of the interesting ways that these iconic animals ensure the survival of the ecosystem is by digging. They’re known to dig up tubers and roots, which in turn provide food for other animals, and this activity in itself promotes healthy plant growth. Where there are enough resources for the grizzly bear to thrive, other species will thrive as well.
One of the major benefits of coyotes in an ecosystem is that they boost biodiversity. They do this by being an apex predator and preying on things like skunks, foxes, and raccoons, keeping their populations in balance.
Being opportunists, these animals will prey on many other species and it doesn’t matter if the habitat is fragmented, coyotes are still able to make a difference. For example, where they exist alongside human habitations, they will control the populations of pests such as mice and rats.
What’s more, they are easily able to adapt to changing conditions but these are incredibly feared and persecuted animals. In order to protect them, there are a lot of educational programs in place.
10. Sea Otters
The sea otter primarily feeds on sea urchins, and this predatory behavior is what makes them such an important keystone species, controlling the populations. This has a direct impact on the habitat of other species within the ecosystem, such as crabs.
The reason for this is that if sea urchin populations were to get out of control, they would use up all of the kelp seaweed which crabs use for shelter, therefore putting the crab population at risk. What’s more, without sea kelp, there would not be an adequate barrier for shoreline erosion.
If that wasn’t enough, we have to keep in mind that kelp seaweed acts as a sponge for carbon dioxide, so having an abundance of it means we can lessen the risks of climate change.
11. Saguaro Cactus
The saguaro cactus can live for over a century and may grow to more than 40 feet (12 meters) in height. Not only are they magnificent desert plants in terms of their appearance, but they also play an important role in the health of the desert ecosystem.
Many plants and animals rely on these desert giants for food and shelter. When they’re removed, this can have a devastating impact on the local ecosystem. In terms of shelter, it’s thought that these cacti provide shelter for more than 100 species, including bats, birds, and mammals.
Sadly, the saguaro cactus is often cut down long before its prime, and there are now protection plans in place to keep it safe.
Krill are a primary food source for many marine creatures such as whales, penguins, and seals. Because of the nutrients these krill provide, this ensures these animals have a viable diet that ensures their survival.
This is because krill feed on phytoplankton which is rich in amino acids and other nutrients that these animals would otherwise have no access to.
In areas like Antarctica, krill are incredibly important keystone species, and their abundance is so because of the dense populations of phytoplankton in the area. However, there are serious concerns over the number of krill in the Southern Ocean, and recent studies show that populations could have dropped by up to 80%.
The hummingbird is the smallest type of bird in the world, and they’re loved by many for their beautiful appearance and gentle nature. But they’re important to our world for many other reasons, including the fact that they’re a keystone species.
Hummingbirds are pollinators, and in rainforest ecosystems, their extinction would also mean the extinction of many plant species that rely on them to aid reproduction. What’s more, invasive species may take over and this could in turn threaten the survival of animals that rely on the native plants.
Termites are ecosystem engineers creating termite mounds that are not just beneficial to these creatures but many others within the ecosystem.
Termite mounds can get incredibly large and this means they provide shelter for a whole host of animals. Mongooses, for example, will set up home inside a termite mound, and lions will climb on top of the mounds to get a better view of their surroundings.
Even species of birds, like the barbet, make use of old termite mounds for shelter. Without them, none of these animals would benefit.
15. Great White Shark
The great white shark has something of a bad reputation. However, attacks on humans are rare, and when they do occur, it’s usually a case of mistaken identity. The main part of their diet is fish and this ensures that marine populations are kept in check. Without the great white shark, other fish species could blow up, and the competition for resources would lead to the extinction of the weakest species.
Moreover, sharks will typically prey on the weakest and most vulnerable fish, and just like the jaguar we talked about earlier, only the strongest of the species will survive.
These huge predatory fish also play a part in the health of the ocean since they feed on carcasses that have fallen to the sea bed.
What are the Consequences of the Loss of Keystone Species?
It’s clear to see that keystone species play an important role in the ecosystems around the world, but what would happen if we were to lose them? The effects of the loss of even a single keystone species could be felt across the wider ecosystem and may even affect humans.
If a keystone species was lost or removed from an ecosystem, this would cause the collapse of the whole system. This would be a result of some species increasing in number while others declining. This imbalance, along with increased competition for resources, means the ecosystem would no longer be stable.
Food Chain Is Affected
The removal of one species from the food chain will have a direct impact on everything else within it. Usually, there is a trophic cascade from the top down, meaning that the apex predator controls the population of the rest of the chain. However, when this predator is removed, there is a risk that other species will decline in number.
With a risk of extinction to many species within the ecosystem, the removal of a keystone species means less biodiversity.
What’s more, there’s also a risk that strong invasive species could take over the weaker native species, further destroying the biodiversity.
Nutrient Cycling Imbalance
It’s essential that an ecosystem has a good balance of nutrients to thrive. However, many keystone species cycle nutrients like nitrogen and phosphorus. Without this, the soil quality is reduced meaning that plant species are less likely to thrive and the animals that rely on them for food and shelter will also be affected.