Why Do We Call Organisms Ecosystem Engineers?

Engineers use scientific principles to create solutions to meet people’s needs—for example, building a bridge that connects two pieces of land. To build a bridge, a civil engineer needs to calculate all the physical forces, including the vehicles running over the bridge, the weight of the materials, and natural forces such as gravity or wind. Civil engineers are not the only engineers that make our lives a little easier. There are mechanical, chemical, agricultural, medical, and many other kinds of engineers. But have you ever heard about ecosystem engineers?

Unlike other types of engineers, people cannot become ecosystem engineers—you must be born one! Ecosystem engineers are organisms that, through their biological traits, can modify, maintain, and even create ecosystems [1]. Many organisms such as trees, grasses, or kelp algae are considered ecosystem engineers. But beavers are the perfect example of this concept.

Get to Know the Beaver

Beavers are rodents, just like guinea pigs, hamsters, rats, and capybaras (Figure 1). Beavers are semiaquatic organisms. That means they can live on land as well as in water, although they seem more comfortable in water. There are two species of beavers, the American (Castor canadensis) and the Eurasian beaver (Castor fiber) [2]. Both species have very specific and essential niches, and despite being relatively small (both species are around 1 m long), entire ecosystems depend on them. Thus, beavers have earned the title of ecosystem engineers.

Beavers live along medium-sized rivers and eat plants and algae. They feel a little more comfortable in water, as it offers them protection from predators such as wolves, bears, or bobcats. Water also gives them the opportunity to build their homes. Like other animals, beavers need a place where they can rest, eat, and take care of their families. Instead of just digging a burrow on the margins of a river, beavers are unique in that they build their homes surrounded by water. These structures are called lodges (Figure 2). Lodges are made of wood that beavers collect and arrange into structures that can protect them from swimming predators such as alligators and snakes. These structures have multiple entrances and places where beavers can hide, rest, and have babies. Beavers also build dams to slow down the flow of the river, allowing them to swim more easily.

By moving wood around, beavers engineer the ecosystem. To cut down trees that are far away from their lodges and dams, beavers dig channels through the land. Those channels fill up with water and allow beavers to reach distant areas without having to walk [2]. Imagine dragging a log across the land—that would require much more strength than moving it while it is floating on the water. Using water allows beavers to transport wood and plants more easily.

How Do Beavers Create Ecosystems?

You might be asking yourself why beavers are considered ecosystem engineers if their actions only make their own lives better. It might seem like beavers are selfish, hoarding water and wood for themselves and building their comfortable, safe, floating mansions with private pools. But this seemingly selfish behavior actually generates all the conditions necessary to create and maintain ecosystems.

While beavers search for food or wood for their lodges and dams, they cut down surrounding trees—some of which may already be old or too big. The trees (especially the big ones) capture light and nutrients, which other plants need, too. When a tree falls, light penetrates the canopy and reaches the soil, where many seeds and small plants are ready to receive it and start growing. This increases the diversity of plants in the area and allows younger plants to grow and reproduce.

Beavers may not use the whole tree. Instead, they might select some branches and leave the logs behind. The remaining dead wood provides food and nice and cozy homes for interesting organisms called detritivores. Some detritivores are fungi, bacteria, insects, worms, and crustaceans.

By digging the channels through which they travel and transport wood, beavers provide water to places where it was not so easily available. With that, they promote the growth of some groups of plants and sometimes generate areas where new meadows and wetlands can form. Naturally, the land becomes wetter, and some of that water may contribute to the natural underground water storage known as groundwater. Finally, beaver dams can become a place where other animals can obtain water, even wolves, bears, and bobcats.

In the dammed-up water itself, changes are also impressive. Here, some species of fish, water-borne insects, and other aquatic creatures can live without being carried away by strong water flows. The reduced water flow can also increase the accumulation of sediments (sand and mud) above the dam. Those sediments are rich in nutrients, which are necessary for the growth of water plants. Eventually, beaver dams can become areas where multiple plant species can grow, and of course, the fish and other animals can eat some of them. The small animals do not only get a nice place to live—the branches and logs that make the lodges and dams also create small, safe environments that can be used as nurseries where the next generation can grow.

So, in some ways, beavers are not just benefitting themselves. Instead, they create a spot where many other plant and animal species can grow and obtain water, even the beavers’ predators. So, maybe they are not so selfish after all!

Beavers can Help us to Help the Environment

Due to all of the benefits we just mentioned, beavers have been used in efforts to bring back the natural conditions of ecosystems. Beavers can assist with restoration (ecosystem recovery) in areas where humans have not succeeded at doing so—and at a much lower cost than using lots of people and big machines [3, 4]. Because they do not need us to do their job, they are considered a nature-based solution. In many places of the world, it has been shown that the reintroduction of beavers helps the recovery of ecosystems—not only for other animals and plants, but for the structure of the entire landscape [2, 4].

Why Not Use Beavers Everywhere?

Unfortunately, introducing beavers in areas outside their natural areas can create larger problems. For example, North American beavers introduced to Argentina (South America) in the 1940s have expanded their territory to neighboring Chile. These beavers have caused trouble because they are not a natural part of South American ecosystems. They take the resources other species need and destroy the natural structure of the region’s ecosystems (Figure 3) [5]. In South America, the plants do not benefit from beaver behavior because the plant species are different from those in the natural habitats of beavers. These plants get eaten and chopped down but cannot grow back as fast as the beavers destroy them. Also, because some local fish are not used to beaver dams, it can make their migration impossible. Moreover, beavers have no natural predators in these regions, so their populations can grow too quickly.

A New Perspective

Now you know why beavers are considered ecosystem engineers and how multiple types of organisms and even entire ecosystems depend on them. You have also learned why it is not a good idea to introduce beavers everywhere to restore ecosystems. Just like human engineers, ecosystem engineers each have their specialty. Maybe you are now curious to know about other types of ecosystem engineers—where they live and what they do? If so, check out this article, or this one.

Glossary

Ecosystem Engineers: ↑ Organisms that through their activity are able to build and modify large parts of an ecosystem.

Ecosystem: ↑ Set of living and non-living elements interacting in a specific space and time.

Biological Traits: ↑ Specific characteristics of organisms that allow them to interact with their environment, for example their body shapes, behaviors, sizes or types of food they eat.

Rodents: ↑ Group of mammals characterized by upper and lower pairs of continuously growing teeth.

Niche: ↑ Set of environmental conditions to which organisms are adapted.

Canopy: ↑ Upper part of the plant community, generally dominated by trees.

Detritivores: ↑ Group of organisms that eat the remains of dead trees and other dead organisms, as well as leaves and droppings.

Migration: ↑ The intentional movement of a species between distant locations to search for better living conditions. For example, European migratory birds migrate to Africa during winter to escape cold weather.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

The doctoral studies at the Helmholtz Centre for Environmental Research—UFZ of HERA are currently founded by the Helmholtz International Research School TRACER (Trajectories Towards Water Security), grant no. HIRS-0017. Thanks to Sophia Hildebrandt for her comments which helped to improve this manuscript.