Tahoe yellow cress (Rorippa subumbellata Roll.) Recovery on the Lake Tahoe Basin Management Unit

Tahoe yellow cress (Rorippa subumbellata Roll.) is a rare plant that only occurs on the shores of Lake Tahoe in California and Nevada. The species is listed as endangered by the State of California and as critically endangered in Nevada. The U.S. Fish and Wildlife Service identified Tahoe yellow cress as a candidate species for listing in 1999 under the Endangered Species Act of 1973, as amended. The Tahoe Regional Planning Agency also protects this species under its Code of Ordinances and Goals and Policies.

Because of the growing concern regarding the long-term survival of Tahoe yellow cress in the Lake Tahoe shorezone, conservation efforts have been undertaken to recover the species and ensure that it is protected. A strategy was completed in 2003 that identifies goals and objectives to meet the conservation and management needs of the species. The strategy includes an experimental program, monitoring component, and an adaptive management process, which assists land and resource managers in making informed, practical decisions by filling in data gaps and providing an ever-increasing knowledge base. Thirteen partners signed the strategy. Successful implementation of the program is expected to preclude the need to list the species under the ESA, as well as allow the states of California and Nevada to downlist or delist the species.

A relatively long survey record has been compiled for this species, beginning in 1978 through the present. Annual surveys are conducted as part of the conservation strategy to determine population numbers, site occupancy, and general disturbance regime. The species is well adapted to the dynamic nature of the shorezone and, in general, when the lake level is low, the plant is able to colonize more sites and, conversely, when the lake level is high, the plant and its habitat become inundated. The partners to the strategy have dedicated more time to the survey efforts in the recent past, which has allowed for a very thorough assessment of the plant’s distribution. The species is concentrated on the south and west shores of the lake, with a few scattered occurrences on the north and east shores. The species is most affected by recreational use of the beaches and development of marinas, boat ramps, and piers, which result in trampling and degradation or loss of habitat. However, the partners are working together to resolve these issues in the most feasible and efficient manner through the strategy.

While the strategy was signed as recently as 2003, conservation and management actions had been implemented beginning in the 1980s. Efforts such as fencing and outplanting have had varied results. Activities were implemented in 2003 as part of the conservation strategy, that included but were not limited to seed collection, greenhouse propagation, and an expanded genetics analysis, all of which were in support of the pilot experimental outplanting project that will inform management regarding restoration and/or augmentation of Tahoe yellow cress occurrences. Preliminary results of these efforts show that outplanting may be a feasible and practical approach to facilitate long-term survival of the species in the face of impacts from various land uses. This type of work will continue into the near future, until protocols can be developed that will serve as a guide to restoration and mitigation actions. In addition, a considerable effort to develop and implement a stewardship program, designed to engage private landowners willing to participate in the conservation of Tahoe yellow cress, is ongoing.

Funding to support implementation of the conservation strategy has come from a variety of sources, including earmarks from the U.S. Fish and Wildlife Service, grants from the Bureau of Reclamation and Nevada Department of Conservation and Natural Resources, capital improvement funds from the California Tahoe Conservancy, and in kind contributions from all partners. The most recent source of funding has been the Southern Nevada Public Land Management Act. The first round of funding ($100,000) came in 2005 and supported a genetic analysis, experimental outplanting and monitoring efforts, and annual surveys and reporting performed by the Forest Service. Funding is expected to be obtained through subsequent rounds of SNPLMA, which will ensure implementation of the strategy continues successfully.

The data obtained each year through annual surveys and other actions contained in the strategy are used to guide regulatory and land management agencies in their conservation and management efforts regarding Tahoe yellow cress and its habitat. Continued commitments from stakeholders and successful implementation of the conservation strategy should ensure the long-term survival of the species in the Lake Tahoe Basin.

Contacts

• Joseph Keely, Ecosystem Conservation Staff Officer, (530) 543-2661