Vegetation Stewardship

Biologists, ecologists, and vegetation managers of the GGNRA employ a full suite of vegetation stewardship techniques to maintain and enhance the natural resource values of the Park. All work done to remove invasive species from parklands is analyzed via Integrated Vegetation Management (IVM) techniques, where all potential methodologies are carefully considered in concert with a detailed understanding of the ecology, environment, and potential impacts of each approach.

In general, the Park employs cultural and manual vegetation management techniques whenever possible, including the extensive use of volunteers. However, it is sometimes necessary to use low-impact herbicides to complete targeted weed-control projects with the least possible ecological impact.

When an herbicide treatment is chosen, it is based on the best available science and submitted to a California Department of Pesticide Regulation (CADPR) licensed Pest Control Advisor for inclusion an annual Pesticide Recommendation specific to that herbicide, application type, and location. Further, this approach is incorporated into GGNRA’s Integrated Vegetation Management Workplan which is reviewed annually for Federal environmental compliance. All applications within Parklands are done by staff or contractors holding valid CADPR Qualified Applicator Licenses (QAL) or Certificates (QAC).

GGNRA maintains an extremely high standard of care when using any herbicide formulation for weed control. It is an important tool in our vegetation management toolkit as we preserve and protect the unique natural resources of the Park. Manual control methods, including digging, pulling, covering, masticating, or mowing/chopping can all have significant effects on the landscape in the form of soil disturbance and impact to native species.

For extensive infestations of high-priority weeds, the environmental impact of manual control is often a ‘red flag’ when evaluated through Integrated Vegetation Management. Selective herbicide treatments, specifically targeting only the invasive plants that need to be removed, allow for adjacent native plants to fill in when the weedy species dies back. Herbicide applications also allow for minimal disturbance of the structural component of habitats in the short term, thereby avoiding acute impacts to native animal and insect species.

As part of our weed control toolbox, we sometimes use formulations of herbicide with the active ingredient glyphosate. This herbicide has the advantage of being effective at very low concentrations, having low toxicity, working on both grasses and broadleaf plants, and readily binding to soil particles so that there is little to no potential for runoff, groundwater impacts, or impact to surrounding native plants.

Herbicide treatments only occur when temperature, humidity, precipitation, and wind conditions are appropriate, in accordance with the Environmental Protection Agency authorized product label and the Pesticide Recommendation, so that no off-target impacts occur. Where treatments may be close to trails, trails are closed during treatment and within a short time frame afterward for the herbicide to dry on the plants.

No weed control work done in GGNRA is done without careful consideration. Herbicide work is always done with a deliberative, professional approach as befits the complicated stewardship responsibilities of National Park Service lands. Preservation of these unique landscapes requires the use of all appropriate tools so that future generations can continue to enjoy our shared natural resource heritage.