A Silent Threat to Our Coastal Wetlands

Climate Change | Wetlands

by Leah Diehl-Koroly

While walking along the coast one can experience the smell of the salty ocean, the sight of birds flying overhead, plants blowing in the wind, waves gently rippling along the shore, and the feel of a cool refreshing breeze. Coastal wetland areas such as Batiquitos Lagoon and San Dieguito Lagoon are peaceful and beautiful places to visit and are enjoyed by many in the community.

San Diego County is home to several of these coastal wetlands where water meets land. The two mentioned above are among the eleven marine protected areas within the county. Marine protected areas, or MPAs, are designated locations where there is an emphasis on preserving the health of the ocean and its inhabitants.

At first glance, it’s obvious why coastal wetlands are appealing with their natural beauty, but there is more to them than meets the eye. They provide critical habitat to many plant and animal species. What makes these species so special is that they are only found in very specific areas and many have incredible adaptations that allow them to live exclusively within the wetlands. It is estimated that more than 40% of federally threatened and endangered species call these wetlands home [4].

Unfortunately, only 5% of these wetlands remain in California [1]. And they face immense pressure from human-induced threats such as climate change and continual development to meet the needs of a growing population. Another threat that has become particularly problematic is invasive plants. Invasive species are those that are non-native, have been introduced and have an adverse impact upon an ecosystem. Why are invasive plants of concern? They are able to outcompete native plants as well as alter interactions within the plant community. This means that the number of native plants could be decreased and the remaining population be negatively affected.

“Native plants can often support 10 to 50 times as many species of native wildlife as non-native plants.” – California Native Plant Society

Invasive Wild Radish- Raphanus sativus

Why does this matter to us humans? Well, native plants are a critical part of maintaining the balance within ecosystems that allow processes such as nutrient cycling to function properly. Nutrient cycling is particularly important because the flow of nutrients throughout an ecosystem allows the status quo to be maintained. If this status quo changes, there can be imbalances in pH levels of soil and water which can impact the survival of the organisms within the ecosystem. Without native wetland plants that turn phosphorus and nitrogen into other beneficial organic forms, these nutrients will build up in the water and impact water quality, cause toxic algae blooms and ultimately harm human health. Another issue with these invasive plants, especially ones like black mustard, is that they contribute to the fire risk of an area. While they may be pretty to look at in the spring, once these plants are done blooming and dry up in the summer sun, they become fire hazards that change the landscape into flammable grassland.

Invasive Black Mustard- Brassica nigra

However, there is good news. In the last few decades, there has been an increased focus on habitat restoration and invasive plant removal in coastal wetlands here in San Diego County. Many local organizations such as WILDCOAST and the Batiquitos Lagoon Foundation have partnered with each other to perform restoration work with the hopes of not only preserving but enhancing wetland ecosystems. In a recent study done at the Batiquitos Lagoon, it was found that when comparing two areas within the lagoon: one that had undergone invasive species removal five years prior with one that hadn’t, in the area where invasive plants were removed, only 5% of the plants were invasive compared to 22% of the plants in the unmanaged site [3]. This shows that habitat restoration efforts are effective and make a difference in both the presence and spread of invasive plants.

Preserving biodiversity through efforts such as invasive plant removal not only enhances ecosystem services but the health of the community overall. But we can’t rely solely on these organizations to do the heavy lifting for us. In order for long-term success in the reduction of invasive species, we all have a role to play. You may be asking, “What can I do to help?”

There are simple ways for each of us to make a difference:

  1. Plant native plants in your garden.
  2. Clean the bottom of your shoes before visiting wetland areas.
  3. If you come across an invasive species, report it. You can contact the Invasive Species Program at (866) 440-9530 or email invasives@wildlife.ca.gov.
  4. Get involved in local restoration efforts.
  5. Spread the word!
  6. Donate

With your help, our precious wetlands will be protected for our own continued enjoyment and the enjoyment of future generations. If you would like to get involved to support future restoration efforts or would like more information, please contact: info@wildcoast.org.

Native Bush Sunflower Encelia californica

Leah Diehl-Koroly is a graduate student at Miami University in Oxford, Ohio completing her Master’s Degree in Biology through Project Dragonfly’s Advanced Inquiry Program.



  1. Armitage, A. R., Jensen, S. M., Yoon, J. E., & Ambrose, R. F. (2007). Wintering shorebird assemblages and behavior in restored tidal wetlands in southern California. Restoration Ecology, 15(1), 139-148. https://doi.org/10.1111/j.1526-100X.2006.00198.x
  2. D’Antonio, C.M. (1993). Mechanisms controlling invasion of coastal plant communities by the alien succulent Carpobrotus Edulis. Ecology, 74(1), 83. https://doi-org.proxy.lib.miamioh.edu/10.
  3. Diehl-Koroly, L. (2020). Diversity of plants in coastal wetland habitat of Southern California. [Unpublished manuscript]. Miami University.
  4. Flynn, K. (1996). Understanding wetlands and endangered species: Definitions and relationships. Extension Publication ANR-979, Alabama Cooperative Extension System.
  5. Guido, A., & Pillar, V. (2017). Invasive plant removal: assessing community impact and recovery from invasion. Journal of Applied Ecology, 54(4), 1230–1237. https://doi-org.proxy.lib.miamioh.edu/10.1111/1365-2664.12848
  6. Morzaria-Luna, H.N., Castillo-Lopez, A., Danemann, G. D., & Turk-Boyer, P. (2013). Conservation strategies for coastal wetlands in the Gulf of California, Mexico. Wetlands Ecology and Management, 22(3), 267–288. https://doi.org/10.1007/s11273-013-9328-0
  7. Mack, R. N., Simberloff, D., Mark Lonsdale, W., Evans, H., Clout, M., & Bazzaz, F. A. (2000). Biotic invasions: causes, epidemiology, global consequences, and control. Ecological Applications, 10(3), 689–710.
  8. Zedler, J.B. & Kercher, S. (2004). Causes and consequences of invasive plants in wetlands: opportunities, opportunists, and outcomes, critical reviews in plant sciences, 23:5, 431-452, DOI: 10.1080/07352680490514673
  9. Zedler, J. B., & Kercher, S. (2005). Wetland resources: Status, trends, ecosystem services, and restorability. Annual Review of Environment & Resources, 30(1), 39–74. https://doi.org/10.1146/annurev.energy.30.050504.144248