Keystone Species

Learn why keystone species are essential and what threats they face. In a famous experiment in 1963, biologist Robert Paine removed starfish, a top predator, from a rocky shoreline and documented the cascading damage to the marine food web that followed. His work led directly to the keystone species concept, which describes the outsize impact certain species have on their habitat relative to their abundance.

• There are several types of keystone species. Predators, such as lions, affect populations of prey—animals caught and killed for food. Some prey, such as krill in the Southern Ocean, form the base of an entire food web. Ecosystem engineers, such as beavers and elephants, modify and maintain landscapes. Mutualists, such as flowering plants and pollinators, engage in vital reciprocal relationships. Plants like the saguaro cactus, provide food and shelter for other species.
• While most research has focused on mammals, ecosystems have keystone plants and aquatic species, as well as fungi essential to soil health. Here is a list of keystone species by habitat.
• Cultural keystone species are the plants and animals that play a fundamental role in Indigenous communities' diet, materials, and medicine and feature prominently in their ceremonies and stories. Eastern white pine is a keystone species for the Kitcisakik Algonquin community of western Quebec.
• Many keystone species are endangered or threatened. These include jaguars in the Americas, ivory bush coral in the Caribbean and Gulf of Mexico, and mosses and liverworts, which are a critical part of European peatlands.
• Many of the threats to keystone species are the same ones adversely affecting other species around the world, including overfishing, overhunting, overgrazing, habitat conversion, industrial agriculture, toxic chemicals, pollution, invasive species, and climate change. See Insects Nexus and Mangroves Nexus for examples.
• The loss of a keystone species can cause ripple effects in ecosystems both downward and upward, called trophic cascades. These effects have been observed globally and often result in weakened food webs. Examples include effects on herbivore behavior and forage when leopards and African wild dogs were removed in Mozambique, marine food web destabilization after cod population collapse in Maine, and the decline of coral reef health when sharks are absent.
• Trophic cascades can result in midlevel predators gaining prominence, as coyotes did when wolves were removed. When dingo populations in Australia were reduced, red fox populations increased, impacting smaller mammals.
• Solutions exist. Ranchers are reducing livestock-predator conflicts. Large carnivores are growing in numbers across Europe. Humans and lions are living peacefully in the Kalahari. New technologies are being applied to reduce human-shark conflicts.

Join a support group protecting and restoring keystone species, particularly Indigenous and traditional communities. There are many organizations and agencies working on behalf of keystone species around the world (see Key Players below for more). Find groups that respect and collaborate with traditional custodians while supporting existing conservation efforts.

• The Cascade Forest Conservancy partnered with the Cowlitz Indian Tribe in Washington State to reintroduce beavers into parts of the Cascade Mountains where they had been missing for ninety years.
• Rocky Mountain Wolf Project is one of many regional wolf-specific organizations in the United States.
• Panthera International focuses on the conservation of the world’s forty species of wild cats and the ecosystems they inhabit.
• Rewilding Chile is an example of an organization whose conservation of a keystone species, the Andean Huemul deer, will meet more complex regional conservation goals.
• Living with Lions weaves research, conservation, and education to help people in Sonoma County, California, coexist with mountain lions.

Provide a buffer zone for local conservation efforts at home. The way we engage with our shared spaces, such as our backyards or community parks, can help keystone species. Buffer zones—habitats at the edge of properties adjacent to or acting as wildlife corridors—reduce human-wildlife conflicts (see Wildlife Corridors Nexus).

• Work with neighbors to develop a private land corridor or buffer zone, such as in Byron Shire. Include safety features like predator-friendly fencing so that animals can safely pass through while humans and domesticated animals can stay safe.
• Join forces with neighbors to get your community certified as pollinator-friendly or as wildlife habitat, as this neighborhood did in North Carolina.
• Encourage neighbors and nearby businesses to stop using rat poison and bait boxes. Effective nontoxic alternatives like Integrated Pest Management focus on excluding rats from buildings and food storage and sanitation measures.
• Build partnerships with government and NGOs to connect backyard efforts with green infrastructure, land acquisitions, conservation partnerships, and urban wildlife projects.

Prevent illegal wildlife trade. Illegal wildlife trade is a billion-dollar industry that fuels the poaching of wild mammals, creating cascading negative impacts on surrounding ecosystems, human health, and local economies. Examples of highly trafficked keystone species include elephants, rhinoceros, and pangolins.

• Do not buy endangered and exotic animal products. This can include corals, fur, ivory, leather, and shells.
• Avoid consuming exotic food products, including wild meats and shark fin soup.
• Report wildlife crimes to your local wildlife agencies. Report wildlife trade by taking photos and sending reports to a global wildlife monitoring nonprofit, TRAFFIC.
• Sign the Stop Wildlife Crime campaign to support more vigorous poaching enforcement and long-term demand reduction efforts by governments.
• Support NGOs that fight poaching and illegal wildlife trafficking. Lists of organizations can be found at One Green Planet and Oyster Worldwide.

Support responsible ecotourism. Ecotourism can financially empower local communities to participate in protecting keystone species by reducing poaching and protecting neighborhoods from wildlife encounters. Not all ecotourism outfits have net benefits for the ecosystem. Here are some examples of certifications to look for.

• Many companies are certified by statewide or regional agencies. Some gold standards include Australia and Costa Rica.
• Conservation organizations like Amazon Conservation’s EcoLodges also offer certification.
• Global Sustainable Tourism Council and Rainforest Alliance are international certification bodies.

Stop keystone species depredation. Conflicts can arise between keystone species and agricultural operations. Predators might kill livestock, although deaths by predators are often lower than from other factors. The presence of ecosystem engineers and mutualists might conflict with farming or ranching goals. Often, these conflicts can be avoided or mitigated with the use of regenerative agricultural practices, involvement in collaborative conservation, employment of new technology, and compensation for loss. Examples:

• When a farmer in Nevada stopped depredating beavers while implementing rotational cattle grazing and riparian buffers, his land soon had cleaner and more abundant water.
• The Western Landowners Alliance works across the American West to implement collaborative conservation programs and policies that benefit wildlife and landowners.
• Winemakers in France are investing in hedgerows at the end of fields to provide habitat for keystone pollinators, improving crop success. Tools like Bumble-Beehave or the Xerces Society’s guidelines allow farmers to plan pollinator-friendly farm management.
• A farmer in Montana utilized the USDA’s technical and financial assistance to grow trees and shrubs, including the keystone elderberry for keystone pollinators. These plantings, in turn, reduce erosion and compaction and improve soil health on his farm overall.

Improve livestock protection practices. Livestock can be protected from predators by the use of human herders, guard dogs, electric fencing, and scare devices. Much can be learned from pastoralists who have been coexisting with predators for generations. Livestock protection will vary greatly depending on location, resource availability, and the behavior of local predators. Common protection efforts include:

• Livestock penning at night; motion-detected lighting; food cache, carcass, and garbage containment.
• Building fences with wild animal movement in mind. Simple fixes like removing unused fencing or raising the height of the bottom cross-beam can meet farmers’ and ranchers’ needs without triggering trophic cascades. See Wildlife Corridors Nexus for more.
• Choose deterrents based on the species. African elephants were successfully deterred from entering spaces using African honey beehives, which the elephants dislike.

Support efforts to protect and rehabilitate keystone species habitat. Removing invasive species and reintroducing keystone plants like oaks and willows can support the return of other animals and plants that rely on them, such as this one in the UK involving the reintroduction of beavers. Restored ecosystems provide predators with access to preferred prey, which lessens the pressure on livestock. There are many ways to rehabilitate habit (see Degraded Land Restoration Nexus). Other options:

• Many landowners can sell or gift their land to a local conservation organization, community trust, or land trust.
• Landowners can partner with conservation groups and governments to advance conservation efforts with fewer impacts on ranch/farm operations like landowners abutting South African parks did.
• A two-year project in the UK found that brush piles and banks effectively increased rabbit activity and promoted rabbit populations' breeding and restoration.
• A farm and distillery in northern Minnesota got Bee Friendly certification to demonstrate to customers that their products support keystone pollinators.
• Get technical assistance and resources from conservation groups like residents across Sonoma County, California, do with Living with Lions.

Work closely with all stakeholders, especially Indigenous communities, landowners, community members and leaders, government officials, and other agencies. The development and implementation of projects should incorporate local community perspectives and needs.

• The Haida Nation’s stewardship included efforts to restore sea otters and evaluate their restoration’s effect on their region.
• Citizen scientists can contribute to marine scientific knowledge while improving the engagement of communities adjacent to oceans.
• The Human-Wildlife Conflict & Coexistence Specialist Group tracks resources and researches how conservation groups are engaging locals.
• If the conservation team is not from the community, include local community members in the core team, like in Kenya, where herders manage a conservancy.

Focus on the entire food web. Some conservation efforts focus too narrowly on reintroducing or stabilizing a population of one keystone species without sufficient plans to manage larger effects on the food web.

• Use food webs to guide ecosystem management and conservation efforts to ensure that efforts get the intended results.
• Plan to develop new management stages over time as the reintroduced species interacts with and changes the behavior of other species within the ecosystem, requiring a shift in management and conservation.
• Rewilding Europe considers interlocking relationships in their projects. For example, they are boosting rabbit populations in Western Iberia by reintroducing wild horses to create mosaic landscapes through grazing.

How Starfish Changed Modern Ecology by PBS (3 mins.)

Some Animals Are More Equal Than Others: Keystone Species and Trophic Cascades by biointeractive (19 mins.)

From the Top if the Food Chain Down: Rewilding Our World by George Monbiot / TED-Ed

People and Bears Live in Harmony in This Wildlife-Friendly Town by National Geographic (24 mins.)

A Collection of Presentations, Webinars, Documentaries, Films, Trainings, and Conferences by the IUCN's SSC Human-Wildlife Conflict & Coexistence Specialist Group

"Keystone Species 101" by Melissa Denchak NRDC

“Trophic Downgrading of Planet Earth” by Estes et al. / Science

“‘Extinction Breeds Extinctions’: How Losing One Species Can Wipe out Many More” by Umair Irfan / Vox

“Andean Pumas Bring National Park in Argentina Back to Life” by Jane J. Lee / National Geographic

“What Is a Trophic Cascade?” by Ripple et. al / CellPress

“Trophic Cascade,” A Poem by Camille Dungy

The Cougar Conundrum by The Wild with Chris Morgan Podcast (38 mins.)

George Monbiot—Rewilding: How Wolves Change a River by Planet A: Talks on Climate Change Podcast (38 mins.)

A Journey Back to Traditional Ecological Knowledge with Cristina Eisenberg by The Outside Voices Podcast (34 mins.)

Rewilding Earth Podcast