Keystone Species: The Key to a Healthy Environment
A Wildlife Article from All-Creatures.org

FROM Madison Roberts, Animal Law Blog
June 2021

What complicates matters more is that this lack of scientific certainty on Keystone Species has caused the legal system to disregard them.

Grizzly Bear, Jasper National Park, Alberta Canada

What is an ecosystem? According to National Geographic, “An ecosystem is a geographic area where plants, animals, and other organisms…. work together to form a bubble of life.” While every part of the ecosystem is important, certain species are more integral than others. Without these integral species the ecosystem they reside in would collapse. This species is called a Keystone Species.

Keystone Species come in all shapes and sizes. They could be plants or animals, and they exist at varying levels in the food chain. However, it is important to note that while a species may be a keystone to one ecosystem, they could cause harm in another ecosystem.

The first thing to look at when analyzing a Keystone Species is their type. Generally, there are four recognized types of Keystone Species. These four types are explained by Ian Payton, Michael Fenner, and William Lee in their paper “Keystone Species: the concept and its relevance for conservation management in New Zealand.” They are organisms controlling potential dominants, resource providers, mutualists, and ecosystem engineers. The first type is usually a predator that controls the population level of a species under it. Wolves in relationship to rabbits is a good example of this. The second type is most commonly plants.

An example is a fruit tree in the rainforest that provides nourishment for animals during a pinch point where not many other food sources are available. The third type, mutualism, involves the relationship between two animals and how it interacts with the ecosystem. It is easy to understand how two species working together can make both of those species a keystone to an environment by examining the relationship of Bear and salmon in the forests of Alaska. Finally, there are ecosystem engineers. These species literally change the ecosystem when going about their daily life. The best example for this is a beaver that cuts down trees in order to make its home.

For the purposes of this post, we will be focusing on the mutualist and the ecosystem engineer. Bears and salmon are two species crucial to the forests of the Alaska. They are without a doubt Keystone Species and help plants and animals to survive through their interactions together. The way that these two animals impact the ecosystem to such a degree is through their feces. Riparian plants that grow next to a stream with salmon get 18-26 percent of their foliar N from the salmon. Plants with higher foliar N contents are more nutritious and more palatable to the animals that eat them. When a bear consumes salmon, it is consuming the nutrients that the salmon provides. Unlike plants, bears cannot use the nutrients from the salmon that encourages foliar N contents in plants to rise. When the bear is done digesting the salmon for the nutrients that it can use, the bear leaves behind feces that has high foliar N content for plants to absorb into it.

How does this make both the bear and salmon Keystone Species? Without the mutualist interaction between the bear and the salmon that spreads foliar N across riparian forests, there would be significant changes in the ecosystem. It would cause the plants to provide less nutrient benefits to grazers like moose, and in turn cause the moose and other animals to need more food in order to fill that nutritional gap.

The mutualistic interaction of bears and salmon is a good example of how a Keystone Species can benefit an ecosystem. However, there are also examples of how moving a Keystone Species to a different ecosystem can have disastrous effects. For that reason, the next species to discuss is a well-known ecosystem engineer, the beaver.

Beavers are stocky brown animals with flat tails that build their nests and get food by chopping down trees and blocking rivers and streams. In North America, the population and actions of beavers are controlled by bears and wolves. This allows the beavers to serve a beneficial role and help enrich the North American ecosystems that they reside in. However, when the Argentinian military decided they should bring beavers to enrich Tierra Del Fuego the consequences turned disastrous. Because beavers have no natural predator in South America’s Patagonia they have been wreaking havoc on the ecosystem since being placed there.

Beavers are now an invasive species in South America and their population is between 70,000 and 110,000 in Patagonia and Tierra del Fuego. The only way to get rid of the beavers is to hunt them, but beaver pelt and beaver meat are not often used and make it financially inefficient. In addition, researchers have found that the actions of the beavers support the welfare of two other invasive species: the muskrat and the mink. The muskrat resides near stagnant ponds which are created by the beaver dams, and the mink like to prey on the muskrat. Therefore, by bringing a species that is a keystone in one habitat to an ecosystem where it has no predators has resulted in disaster. Currently researchers believe that the ecosystem is in a process of meltdown due to the effects of the beaver.

Why does this matter? Keystone Species are integral parts of the ecosystem. They can create benefits and cause disasters. However, there is still no clear way of identifying Keystone Species and even the types of species. Even the Keystone Species types listed above are in contention. What complicates matters more is that this lack of scientific certainty on Keystone Species has caused the legal system to disregard them. In the United States, we have laws that are created in effort to preserve species and ecosystems alike. The Endangered Species Protection Act and NEPA are two examples. However, our legal system fails to look at the dangers of not protecting species that are integral to the ecosystems they try to protect.

What is the point in saying you may not cause the extinction of an Endangered Species, but at the same time allow the injury or destruction of the population of a species it relies on? By not doing more to protect Keystone Species because of the scientific gap left in their research, the legal system is virtually sitting by and waiting for an environmental disaster like that in Tierra Del Fuego. Instead of sitting by and waiting for the science, legal scholars and legislators should be doing their best to protect Keystone Species before science tells them it is too late. 

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