|
Getting your Trinity Audio player ready...
|
Ground squirrels are a keystone species. I know what you are thinking: “That means Gunn High School is the epicenter of the ecological universe.” Or maybe “How is it that mounds of dried grass studded with ankle-twisting holes are a paragon of ecological virtue?”
I had those same questions after I came across the claim. It made me wonder who determines which species are “keystone”, how the determination is made, and whether, perhaps, we aren’t being picky enough. It turns out there have been attempts to quantify the keystone-ness of a species (1), and there is indeed some concern that the concept has been too broadly applied. But I also overlooked some of the ecological value that ground squirrels create.
A keystone species is a species that has a large beneficial impact on its ecosystem, much larger than its population there would suggest. Canonical examples are predators like wolves (in Yellowstone), otters (in kelp beds), and sea stars (in tide pools). These predators are uniquely able to keep their ecosystem in balance by shrinking the numbers of prey species (elk, sea urchins, and mussels, respectively) that would otherwise proliferate, decimate many other species, and greatly reduce biodiversity.
But there are other types of keystone species. Beavers and elephants are examples of “ecosystem engineers”. Beavers build dams that are instrumental in creating and maintaining wetlands. Elephants help to maintain the savannah by eating acacia trees, creating or enlarging watering holes, forging paths, and distributing nutrients via their dung.
Plants can be keystone species as well. Consider mangroves, which are uniquely able to thrive, prevent erosion, and provide shelter and food in the intertidal areas where they are found. Or the saguaro cactus, which provides food, shelter, and hydration in the harsh desert environment.
Those all sound pretty impressive. Are ground squirrels really in the same company? Well, their burrows provide good homes for grassland animals (e.g., burrowing owls, rattlesnakes, even jackrabbits). The ground squirrels loosen the soil and spread seeds around with their digging. They help grasslands to stay intact because woody shrubs struggle to grow in disturbed soil. And the rodents serve as abundant prey for raptors and other small carnivores.
According to one writeup, more than 200 species have been observed using ground squirrel colonies. I have seen jackrabbits, coyotes, and raptors on Gunn’s campus, where ground squirrels thrive. Would they be there otherwise?
The Natural Resources Defense Council has some good descriptions of keystone species, and Bay Nature has a great writeup just on ground squirrels. But there is no single certifying body or certifying metric that is used to determine keystone species. Ironically, the University of California Agriculture and Natural Resources website (ucanr.edu) hosts both a presentation lauding the benefits of California’s ground squirrels as a keystone species, and a lengthy page itemizing the harms done by those “troublesome rodent pests”, complete with detailed descriptions of techniques to get rid of them.
There is general agreement that the “keystone” designation should be context-dependent. Maybe a ground squirrel is a keystone species in the East Bay grasslands, but not in your garden where there are fewer coyotes and jackrabbits to benefit. A mussel-eating keystone sea star was found to have no significant ecological impact in Alaskan tidepools where the mussels they prefer are not present.
To further complicate things, terms for significant species have proliferated. “Foundation species” are critical to their environment but their impact is directly related to their large population (e.g., corals in coral reefs). “Indicator species” are sensitive species, the proverbial canary in a coal mine, whose decline indicates a problem with the ecosystem (e.g., oysters or salmon).
These designations are appealing. It is simplifying and encouraging to think that by paying attention to, and saving, a few select species we will address our biodiversity crisis. But in reality, it is more important to focus on habitat preservation and biodiversity more generally. I don’t think we are losing our burrowing owl population in the Bay Area due to a lack of ground squirrels. To the extent both are suffering, I have to expect it is from habitat loss that is resulting from development, climate change, and industrial pollution.
I am reminded again that our intuition about what makes a rich ecosystem is not especially good. We are very visual and pretty self-centered in our assessments. If an area isn’t pretty, or useful, then we don’t ascribe much value to it. I’m not saying we should go out of our way to protect the thriving, ever-growing population of ground squirrels on Gunn’s campus. (2) But grasslands on the mid-Peninsula and elsewhere sustain a lot of life and ground squirrels play a big role in that.
Notes
1. Scientists experimented with creating a metric for keystone-ness by evaluating changes in biodiversity before and after removing keystone species from their habitats. A Quanta Magazine writeup that discusses this refers to the metric as the “per capita interaction strength.” But it is not used consistently.
2. There have been repeated attempts to reduce the population of ground squirrels on Gunn’s campus. I saw people putting carbon monoxide into the burrows about a year ago. In 2021 they were using traps carelessly, which alarmed neighbors.
Current Climate Data
Global impacts (April 2026), US impacts (April 2026), CO2 metric, Climate dashboard
The last 12 months (May 2025–April 2026) were warmer than any other 12-month period on record for the continental United States. The Arctic’s sea ice was the second-lowest in recorded history.
Curious Photo
This photo and caption appeared (and still appears) in an article in the San Francisco Chronicle about how EV chargers are becoming important factors in home sales. But … do you see what I (don’t) see?
Want to be Notified of New “A New Shade of Green” Blog Posts?
If you would like to be notified of new blog posts, please send an email to notify@newshadeofgreen.com with “Subscribe” in the subject.
Comment Guidelines
I hope that your contributions will be an important part of this blog. To keep the discussion productive, please adhere to these guidelines or your comment may be edited or removed.
- Avoid disrespectful, disparaging, snide, angry, or ad hominem comments.
- Stay fact-based and refer to reputable sources.
- Stay on topic.
- In general, maintain this as a welcoming space for all readers.
