Laguna Watershed Knowledgebase

Distribution of invasive plant populations in California is dynamic, and effectively protecting native flora requires knowledge about where invasive plants are and where they may spread in the future. We determined statewide distribution of 36 invasive plants in California by surveying local resource managers in all counties. Using CLIMEX modeling software, we estimated climatic suitability for each plant throughout California based on its known distribution elsewhere in the world. Combined, these data provide information on potential future spread in the state. This information will be disseminated to support early detection efforts by helping local managers determine which invasive plants are most likely to move into their area. Next, to determine how climate change might affect invasive plant distribution in California, we ran the models again using parameters adjusted for a 3°C increase in annual temperature. Results indicate that overall climatic suitability in California for the 36 combined species would alter little with climate change. However, certain species may be “winners” or “losers”. For example, our models predict that climate suitability will nearly double for castor bean (Ricinus communis) and fountaingrass (Pennisetum setaceum), while decreasing substantially for other species. We will present examples of projected range shifts and changes in suitability for several widespread invasive plants as well as incipient invaders that show potential to expand to new areas of California, with a focus on plants of concern in Sonoma County.