Did you know that San Mateo County Parks are home to 138 rare, threatened, and endangered species? County Parks natural resource managers are responsible for ensuring that these species continue to survive in the face of climate change, which is bringing hotter, drier seasons, increased fire risk, greater extremes in precipitation patterns, and rising seas.

Notably, the most profound threats to biodiversity in County Parks, as well as throughout the State of California, are from habitat loss due to aggressive, invasive weedy species that can out-compete native plants, potentially eliminating many irreplaceable wildlife habitat areas.

Not all non-native plants are considered invasive. Invasives are plants that did not evolve locally, and that are harming native species by monopolizing resources they need to survive, such as light, nutrients, water, and space. Some of the most challenging invasive plants in San Mateo County are pampas/jubata grass, French broom, yellow star thistle, and oxalis.

Controlling invasive plants requires the use of a wide range of tools and techniques, with the goal of long-term control and/or elimination of targeted species. This prescriptive approach, known as Integrated Pest Management (IPM), has become the standard approach for many parks and open space land managers throughout California.

Integrated Pest Management (IPM) Must Take a Multi-Pronged Approach

IPM is a science based, multi-pronged approach that seeks to use the safest, most effective, and most feasible combination of tools and techniques for a given invasive plant management strategy. These can include manual and mechanical control (including hand weeding or mowing), biological control (grazing by sheep, goats, or cattle), and cultural control (prescribed burning, mulching or tarping).

When those methods prove ineffective, land managers sometimes use herbicides to control specific targeted plants, while protecting native vegetation, wildlife, and ecosystems. Herbicide treatment methods at County Parks do not include indiscriminate broadcast spraying. Instead, only the targeted plants are spot sprayed, using the lowest possible volume of the herbicide for effective control, and only when wind and weather conditions meet prescriptions for safe application. With these safeguards strictly adhered to, herbicides are an important component in the maintenance and restoration of wildlife habitats in County Parks.

In 2012, we achieved an important milestone in getting San Mateo County Public Works to use mowing along the edges of county roads instead of broadcast herbicide spraying, except in very limited situations where spot spraying of particularly challenging invasive plants is warranted.

We will continue to support the careful and strategic use of IPM in County Parks and other public park and open space lands, with all applicable and appropriate precautions.