Every species has its place in nature, but certain critters have outsized impacts on the ecosystems around them. Here are some that may be living near you. Ecologists call them keystone species; through some fairly subtle actions, they have a profound effect on everything around them.
Unassuming, oversized rodents with slap-happy tails, beavers make up in engineering skills what they lack in claws, speed, or climbing ability. Their dam-building skills are designed to create a pond where they can dive away from predators and access their lodge from underwater. In the process, they fundamentally alter the world around them. They turn swift flowing streams into still ponds with deep water. Riverside forests become mangrove-like swamps, which changes the composition of the forest edges. Eventually, beaver ponds become wet meadows. Beavers are also voracious enough eaters to fundamentally change the species that grow to fill the meadows they create.
Cute and fuzzy, the photogenic sea otter is one of the biggest ecological catalysts on the planet. Lacking blubber, they eat constantly to keep warm in the cold oceans of California, Washington, British Columbia and Alaska. They eat sea urchins, and a lot of them. Where they’re absent, having been hunted for fur in the 1800s, the urchins have run rampant—eating vital kelp forests down to nothing. The kelp forests serve as nurseries for many species of fish, and also grow thick enough to block waves from hitting the coast. Reintroduction of sea otters has sparked the regrowth of kelp forests—which is now changing the way waves hit exposed shorelines, changing patterns of intertidal life.
The Gray Wolf
An apex predator, the Gray Wolf’s reintroduction sent a wave of effects through Yellowstone National Park in the 1990s. With wolves absent for nearly a century, elk had gotten into the habit of relaxing lazily near streams like a herd of cows. The presence of wolves kept elk on the move—which allows the stream-side willows and vegetation to replenish itself, leading to cooler water and more trout. The wolves also kicked coyotes off the top of the food chain, which allowed the population of ground squirrels to rebound. More squirrels meant more pine cones being moved around, which meant a greater regeneration of pine forests from fire and insect infestations. As a result, the parts of Yellowstone with wolves regenerated far faster from the massive fire of 1988 than the areas without wolves.
The Red-Backed Vole
A humble critter about four inches long, the red-backed vole lives almost entirely underground in the damp forests of the Pacific Northwest. Hanging out amidst the spongy soil and tree roots, its sole source of food is the fruiting body of a fungus that melds with tree roots to pull nitrogen from the soil. The vole’s underground wanderings spreads the fungus throughout the forest. Since usable nitrogen is a limiting factor to plant growth, the vole is a key distributor of a rare commodity, and is essential to the giant trees of the northwest coast becoming so huge. They’re also the main prey source for a more famous creature, the Northern Spotted Owl, which is used as an indicator of ancient forest health because they depend on the voles in these old forests—but unlike voles, they live above ground and are easier to count.
Salmon are many things: an icon of the Pacific Northwest, a major sportfish, an endangered species, the center of a fishing industry, and very tasty. They’re also proof that a fish can build…a forest. When salmon migrate up to their birth streams and die, they bring with them a massive amount of protein and nitrogen that dies and decays into the soil, stimulating plant growth (and eventually being drawn into the fungus that our friend the red-backed vole carts around underground). Where salmon runs are depleted, plant growth is weaker and forests regenerate from disturbances slower than when runs are healthy. That’s why ecologists have begun “fish carcass tossing” to replenish the nitrogen supply in riverside forests.
The Ghost Shrimp
Even more humble than the vole, the Ghost Shrimp both lives underground and lacks the vole’s cute furriness. They live in the mud of coastal salt marshes, where they dig burrows. They are constantly cleaning out their burrows, which leads to a continuous redistribution of sediment. This continuous digging of burrows provides other critters a rent-free place to hide. The combination of water flowing through their burrows and a rich array of critters speeds the decomposition of organic materials in estuaries, making them one of the most productive ecological zones on earth.
So next time you see one of these critters—a cute otter, a majestic wolf, or a tiny little vole you’ve never heard of—tip your hat to them. They’re not just running around making a living and avoiding predators. They’re changing the entire world around us.