SAN DIEGO (July 8, 2025) – San Diego Zoo Wildlife Alliance achieved a historic milestone by introducing the first-ever plant contributions to the Frozen Zoo®—the largest and most diverse collection of cryopreserved (frozen) living wildlife material in the world. The nonprofit conservation organization successfully cryopreserved samples from 18 endangered Nuttall’s scrub oak trees, marking the first time this species—or any plant—is preserved in the Frozen Zoo.
“Cryopreserving Nuttall’s scrub oak is an enormous accomplishment for plant conservation,” said Christy Powell, horticulture manager at San Diego Zoo Wildlife Alliance. “Unlike many species, oaks cannot be stored in traditional seed banks. Cryopreservation offers us an incredible tool to ensure their survival—alongside habitat protections and living collections.”
Nuttall’s scrub oak (Quercus dumosa) is one of the few plant species in San Diego County listed as endangered by the International Union for Conservation of Nature (IUCN), and it is one of San Diego’s only native tree species. Nuttall’s scrub oak conservation is vital not only for preserving botanical biodiversity, but for sustaining the broader ecosystems that rely on oaks. As keystone species, oaks support hundreds of wildlife species and play a critical role in the health and resilience of native habitats.
Partners critical to the cryopreservation of Nuttall’s scrub oak include The Huntington, Cincinnati Zoo & Botanical Garden's Center for Conservation and Research of Endangered Wildlife, and the United States Department of Agriculture Agricultural Research Service’s National Laboratory for Genetic Resources Preservation.
“This is a remarkable example of international collaboration advancing both technology and conservation,” said Katie Heineman, Ph.D., program officer with the IUCN Species Survival Commission Center for Species Survival: Biodiversity Biobanking. “This isn’t just about preserving one species—it’s about providing a roadmap that others can use. By sharing these techniques and increasing capacity with conservation partners globally, we’re accelerating a collective effort to protect oak species and the ecosystems they give life to.”
Nearly one-third of the world’s 450 oak species are at risk of disappearing, with threats ranging from habitat loss to fire and invasive pests. In response, San Diego Zoo Wildlife Alliance’s oak conservation program collaborates with multiple partners—such as the Global Conservation Consortium for Oak led by The Morton Arboretum, The Nature Conservancy, and San Diego Botanic Garden—to safeguard these vital trees with a focus on species native to San Diego, Southern California and Baja California.
Scientists at San Diego Zoo Wildlife Alliance are applying insights gained from preserving Nuttall’s scrub oak to advance cryopreservation techniques for a broader array of California’s native oaks and orchids. As new methods are developed for additional species, the organization is expanding its cryogenic plant collection to serve as a leading repository for plants that depend on this specialized approach.
“As a world-class botanic garden paired with the Frozen Zoo’s unparalleled cryogenic capacity, we are uniquely positioned to push the field of plant cryopreservation to new heights, ensuring a safer future for wildlife, people and the planet,” said Powell.
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About San Diego Zoo Wildlife Alliance’s Frozen Zoo®
The Frozen Zoo® is the world’s first large-scale cryogenic biological bank dedicated to preserving living cells and reproductive material from wildlife—and remains the largest, most diverse collection of its kind. Founded in 1975 by Kurt Benirschke, M.D., the Frozen Zoo today holds cell lines from more than 11,500 individuals representing more than 1,300 species. Stored in liquid nitrogen at minus 320 degrees Fahrenheit, the collection includes cells, embryos and gametes from mammals, birds, reptiles, amphibians, fish and plants. The Frozen Zoo is one of six unique San Diego Zoo Wildlife Alliance biobanking collections that make up its Wildlife Biodiversity Bank. Together these collections offer a variety of approaches to preserving biodiversity. Learn more at sdzwa.org/frozen-zoo.
About San Diego Zoo Wildlife Alliance San Diego Zoo Wildlife Alliance, a nonprofit conservation leader, inspires passion for nature and collaboration for a healthier world. The Alliance supports innovative conservation science through global partnerships and groundbreaking efforts at the world-famous San Diego Zoo and San Diego Zoo Safari Park, both leading zoological institutions and accredited botanical gardens. Through wildlife care expertise, cutting-edge science and continued collaboration, more than 44 endangered species have been reintroduced to native habitats. The Alliance reaches over 1 billion people annually through its two conservation parks and media channels in 170 countries, including San Diego Zoo Wildlife Explorers television, available in children’s hospitals across 14 countries. Wildlife Allies—members, donors and guests—make success possible.
