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Science activity #54493, updated 11 December 2025

Ecosystem Engineering Impacts of Water Primrose in the Delta

Description / purpose

Water primrose (Ludwigia spp.) is a highly invasive, non-native floating macrophyte in the Delta. In recent years, water primrose has extended its niche into marsh habitat, causing extensive mortality of marsh macrophytes including tules and cattails. The goal of this project is to determine whether the growth strategy of water primrose, its allelopathic properties, or factors related to plant community structure are the cause of marsh loss following water primrose invasion in the Delta. Part of this study will identify and map the marshes most vulnerable to loss and quantify the spatial trajectory of marsh loss during the past 15 years. The ultimate benefit will be an improved understanding of the water primrose invasion processes in the Delta, which can be used to prioritize herbicide treatment of this highly invasive plant in marshes most vulnerable to invasion and with the highest habitat value.

Objectives:

1. Determine which water primrose functional traits are the likely cause of marsh loss in the Delta.
2. Determine the effect(s) of community structure on water primrose invasion success and occurrence of marsh loss.
3. Quantify the amount and spatial trajectory of marsh loss due to primrose invasion from 2004 - 2019.
4. Identify and map the marshes that are most vulnerable to loss due to water primrose invasion in the Delta.
5. Disseminate findings to relevant state agencies and additional stakeholders to ensure habitat restoration success and sustainability, and to focus resources on controlling water primrose in marshes most vulnerable to loss and of highest habitat value.

 

Linked science activities

None specified
  • Water primrose invasion Rhode Island, CA
  • J. Drexler collecting data in water primrose invaded tule/cattail stand
  • E. Hestir in water primrose patch
  • Fan boats

Collaborators

Erin Hestir, Principal investigator - University of California - Merced [UC Merced]
Shruti Khanna, Co-investigator - California Department of Fish and Wildlife [CDFW]
Judy Drexler, Co-investigator - U.S. Geological Survey [USGS]
Bailey Morrison, Contributor - University of California - Merced [UC Merced]

Activity status

  • 1 Awarded / Initiating (2020)
  • 2 In progress / Ongoing (2020 - 2024)
  • 3 Complete

Funding summary

Total allocated funding: $952,844

Label Value
Contract # or labor code Q2096002
Implementing organization University of California - Merced [UC Merced]
Funding organization California Department of Fish and Wildlife [CDFW]
Funding Source California Department of Fish and Wildlife CDFW - Prop 1
Date of award 2020-07-15
Date of fiscal year-end 2024-01-01
Total award amount $952,844
State type of obligation Grant
Federal type of obligation Not provided
Reimbursability Not provided
Procurement mechanism Not provided

Location

Subbasins
Delta regions

Geographic tags

SHERMAN ISLAND , LIBERTY ISLAND , BIG BREAK , Latham Slough

Products and outputs

Type Title Description Views
Link Story Map This is the ArcGIS story map that was produced 1

Type and context

Science action area

SAA Action Area 2 (2017-2021): Capitalize on existing data through increasing science synthesis , 2A: Strategically build the capacity to do collaborative science synthesis by implementing the science synthesis mechanisms outlined in the Delta Science Plan , 2B: Identify and prioritize important data sources that should be interconnected to promote collaboration and provide the technology necessary to easily access this information , SAA Action Area 4 (2017-2021): Improve understanding of interactions between stressors and managed species and their communities , 4D: Evaluate the effects of toxicity (e.g., contaminant mixtures, mercury, pharmaceutical products, HABs) on aquatic species survival including possible effects on predation , SAA Action Area 5 (2017-2021): Modernize monitoring, data management, and modeling , 5B: Explore innovative technologies and cost-effective methods for scientific monitoring and analysis of flow, water quality, and ecosystem characteristics...

Management themes

Invasive / non-native species management , Native species management

Science themes

Aquatic vegetation , Habitat changes , Invasive / non-native species , modeling , Tidal wetlands , vulnerability assessment

Types

Targeted foundational research

Science functions

Data application - Data analysis , Data application - Modeling , Data application - Science communication / knowledge synthesis , Research

Management actions

Habitat protection / enhancement / restoration , Invasive species control and management , Wetland resilience , Wetlands

Science Topics

Aquatic vegetation , Emergent macrophytes , Environmental drivers , Floating aquatic vegetation , Habitat , Habitat restoration , Intertidal and transition zones , Invasive and non native species , Landscape change , Landscape metrics , Remote sensing , Residence time , Resilience , Restoration , SAV and FAV , Submerged aquatic vegetation , Tidal wetlands , Wetlands

Lead implementing organization

University of California - Merced [UC Merced]

Partner implementing organizations

California Department of Fish and Wildlife [CDFW] , Interagency Ecological Program [IEP] , U.S. Geological Survey [USGS]

Funding organizations

California Department of Fish and Wildlife [CDFW]

Funding programs

California Department of Fish and Wildlife CDFW - Prop 1

Funding sources

California Department of Fish and Wildlife CDFW - Prop 1