Can the removal of certain species alter an entire ecosystem? It’s hard to believe that other organisms besides humans can have that profound of an effect on the environment. But despite this anthropocentric view, it’s true. There are organisms whose absence can spell drastic change or flat-out destroy ecosystems.
Each ecosystem has an assembly of native species that play key roles in maintaining a balanced and healthy environment. These species are called keystone species and are any organism, from animals and plants to bacteria and fungi, that has such an impact on an ecosystem that without it could spell ecosystem collapse.
Keystone species shape environments.
A recent publication from the Monterey Bay Aquarium further points towards the significance of sea otters for kelp forests, only further solidifying the importance of native species. Sea otters are keystone species and they help not only to positively shape ecosystems but also to preserve environmental health in ways other species can’t.
This study found that over a 100-year span, there was a significant increase in kelp forest canopy in one area – the only area where southern sea otters still prevailed in California after almost being hunted to extinction for their fur in the 1800s.
Without sea otters, the kelp forests along the California coast showed a dramatic decline. Yet, with sea otters present the forests showed overwhelming resilience to change and climate change stressors. This made sea otters the strongest predictor of change in kelp forest canopy coverage across the 100-year study period!
Keystone species are key to environmental wellness.
A keystone species can be anything from a predator to an ecosystem engineer. Yet despite there being different types of keystone species, the overarching theme is that all exert some type of control over their respective environments. This makes the influence these species have widespread and deterministic.
It can be difficult to ascertain who is an ecosystem’s keystone representative without research, but there are many defined relationships that deserve attention. By focusing on remedying problems plaguing key species, we can maximize biodiversity protection which would lead to a healthier environment.
Many species are struggling though.
Like many organisms, keystone species are facing some real issues. Human actions have created problems like habitat destruction or loss, but also poaching, introduction of foreign species, and pollution. Direct human influence aside, climate change presents even more issues. Rapidly changing environments don’t allow organisms to adapt, leading to sizeable loss of life. Many keystone species are endangered and if things continue to trend downward, environmental resilience will be a thing of the past.
Global biodiversity is threatened in many ways, but the stakes are much higher if keystone species go first. Nature is a complex web of interactions and a balance needs to be maintained to offer the best chance of survival with persistent change. Often, messing with the environmental status quo can lead to unforeseen consequences and even ecological disaster.
Invasive and non-native species throw off the status quo.
Although any issue facing native species can tip the scales, one of the biggest issues is the introduction of foreign species. It makes sense that invasive species, or organisms that are introduced to an area they were not found in previously, have the ability to easily throw off the status quo. They undermine native species, readily looking for a new niche to exploit, and are quite successful at doing so.
A non-native species also inhabits an area it didn’t originate from, they didn’t naturally grow or live there before their relocation. Although that’s an eerily similar definition to invasives, that doesn’t mean a non-native species is necessarily an invasive one! However, typically both are spread through human intervention and can be purposeful or by accident. The key difference between invasive species and non-native species is whether or not they cause harm.
Non-native species don’t always harm the environments where they’re introduced, but invasive species always do. Bringing non-native species to a new environment can be either positive or negative (sometimes situationally, depending on how you look at it), but a balance must always be maintained. The introduction of these species turns ecosystems upside down and the entirety of the environment has to learn how to cope or risk extinction.
Can balance in ecological communities always be maintained?
Ecological communities are groups of organisms that interact and coexist well in their environment. These communities are made of groups of native species that maintain the integrity of their environment by working together. That means, there are many interaction points between community members. So, when something happens, a trickle-down effect can be felt for the entire community on some level. Changing the members or population sizes of the community can therefore often produce unexpected, mostly unfavorable, responses and consequences.
Plus, the hubris of man lies in the belief that we know all and are at the focal point of our environment. This couldn’t be further from the truth and has caused many blunders throughout history, both for the environment and in other settings. Without influence, theoretically, balance can be maintained. But in our human-centered world, balance keeps getting overturned making it incredibly hard for the natural world to keep up.
Classic examples of humans messing with the status quo include:
Iceplant (Carpobrotus edulis) was introduced as a way to prevent coastal erosion in California, but had the opposite effect. Coastal communities are already facing a multitude of threats, with many species being critically endangered, making iceplant’s takeover even more frustrating. Read more here and here.
Mongoose (Herpestes javanicus) was introduced to Hawai’i to try and control rats and is now widespread in Hawai’i, O’ahu, Maui, and Moloka’i. This introduction led to drastic declines and even extinctions of many native species and has affected many culturally significant species too. Read more here and here.
Tasmanian Blue Gum Eucalyptus trees (Eucalyptus globulus) were introduced in California, with the encouragement of the government, in the hopes that it would be a reliable and renewable source of timber. With how fire-prone California is, these widespread trees are now posing many threats to wildlife and humans alike. Read more here and here.
Sea Otters show us why keystone species matter.
If a keystone species disappears, no other species would be able to fill its ecological niche, or the role it plays in its environment. These critical organisms maintain the integrity of their environment and without them, their environments just wouldn’t be the same. This idea can be plainly seen by examining the role of sea otters on the California coast!
A keystone species doesn’t have to be the largest or most abundant species in an ecological community but instead has to demonstrate a large influence over community structure and biodiversity in that habitat. Everything in an ecosystem is linked and can influence each other, but what sets a keystone species apart from the rest is how much of a pivotal role it plays in how its environment functions.
Keystone species are only keystone in their defined environments. That is to say that just because a species is key in one ecosystem doesn’t mean it will be in the next. So, viewing the strength of interactions between organisms in an environment is key to understanding the key players in an ecosystem. Knowing this we can gain insight into environmental health or determine the best way to remedy certain environmental problems.
Keystone species are amazing indicators for environmental health.
So, we know keystone species affect the environment, but they can also cause trophic cascades. A trophic cascade is an indirect effect on many species in a food chain when there’s a change in the population size of a single chain member. Because they influence the abundance and types of other species in an environment, we should expect radical change without them.
Keystone species, therefore, can give us insight into whether an ecosystem has the tools to survive change. The absence of keystone species allows other species to take over and diminishes ecosystem viability. Furthermore, without its keystone species, it can be impossible for other community members to withstand environmental changes. To ensure an ecosystem can maintain health and balance, it needs all of its main players.
Ecosystems need all their key players!
That is if you want to give an ecosystem the best chance at surviving environmental changes!
Here are some classic examples of keystone species and the large impact they have on their environments:
Sea otters of course are hugely influenctial for kelp forests. Healthy kelp forests have many benefits, such as serving as nursery grounds for fish, reducing coastal erosion, and increasing carbon storage. The proven positive benefits of sea otters on kelp forests shows that retruning sea otters to their historical range could help recover the dwindling kelp forests (and their benefits) along the California coast.
African savanna elephants also have a keystone effect in eastern and southern Africa. They eat as much as 300 pounds of vegetation per day which preserves the sunny, open spaces where grasses can thrive. They support other herbivores like antelopes and zebras and provide dry and warm soil for smaller animals like mice and shrews to burrow in. This increase in prey species helps to feed carnivores like lions, hyenas, and cheetahs. They also spread seeds with their dung and have been doing so for so long that some plants in those areas evolved to germinate more readily after going through an elephant’s digestive tract!
Bees are another classic example of a keystone species. With the aid of other pollinators, bees support the reproduction of up to 90% of the world’s flowering plants. They pollinate fruits, vegetables, and other crops. They help provide us with food, clothing, and fuel but also help countless other species around the world. Without bees, there would be a botton-up trophic cascade of consequences throughout the food chain.
Nature is holistic.
Understanding the complex and intertwined nature of the world is the key to sustainability. The more we can come to know, the better we can focus conservation efforts. Keystone species are just a part of the whole picture, but they are so important nonetheless. We need to foster native biodiversity on the large and small scale. Utilizing traditional ecological approaches and putting value into nature beyond just monetary value will ensure a stable and healthy planet for the longest amount of time possible.
For the average person, I encourage you to make a mindset shift towards a holistic view. If you have an open garden, favor native plants to foster stability and improve habitat availability. If you’re a fisherman, be mindful of the species you‘re fishing for and catch and release natives and keep non-natives (making sure to check local regulations first though!). Boaters, kayakers, or lake and river-goers should be mindful of vessel laws to stop the spread of invasives and non-natives. Donating to conservation groups is also super helpful and, if you have the means to do so, I encourage you to donate. Let’s start recognizing the beauty and importance nature provides us to ensure a resilient future!