Where Land Meets Mist: Unraveling Fog at Cabrillo

Written by Apprentices Jupiter P and Jacqueline J

Foggy view of the San Diego BayView of fog from Cabrillo National Monument.

Introduction

Cabrillo National Park is home to many plant species that have an important role in the ecosystem. Scientists have discovered that the surrounding fog supports many plant species, acting as a lifeline for the native plant community. There happens to be not a lot of information on fog, so scientists at Cabrillo National Monument built a unique fog monitoring system to better understand how and why plants rely on fog.

Fog is pretty common in San Diego, but did you know it plays a huge role in keeping plants in the environment healthy? Scientists at Cabrillo National Monument wanted to learn more, so they built fog monitoring systems, special machines that track how much moisture fog brings to the plants. We got the chance to ask someone at the park who was there when these fog monitors were set up, and they were able to share really interesting information with us!

Tracking Fog: Cabrillo’s Efforts to Monitor a Vital Water Source

The plants at Cabrillo are greatly impacted by fog settling on their leaves. Scientists at Cabrillo National Monument created a new machine to help measure the different amounts of fog they are getting. The monitors have paddles that mimic several different types of leaves in order to collect and sense amounts of moisture caused by fog. To make sure they were measuring fog and not just rain, the monitors also have small weather stations to check if it’s raining. The best part? They run completely on solar power! From July 2022 to May 2023, fog monitors measured the amounts of fog and moisture and then recorded the information into a data logger. (National Park Service). 

A diagram of labeled parts of a fog monitor Diagram of a fog monitor machine with labeled parts.

Virginia J., a Scientist in Parks Intern, shared that the fog monitoring program helps the park make resource-management decisions, like revegetation projects, based on the different fog microclimates that we were able to visualize throughout the park. Establishing a long-term monitoring program helps us understand how fog is changing over time with climate change. Fog is the main water source during the summers here at the park. With fog being a relatively unknown resource and as we are in a rapidly warming climate, it is really hard to say what will happen in the future. That's why programs like the fog monitoring program are so important, so we can continue to gather data and make resource management decisions supported by data.

Fog Watch: Tracking Changes in Cabrillo’s Ecosystem

Virginia J. also shared with us that since the fog monitors were installed, scientists have already noticed some changes! They are still in the early stages of data collection and analysis, they do not have the full picture of how the data of fog is changing yet. They can't make conclusions at the moment, but every day there is always new data that helps them get closer to their goals. On the other hand, scientists have learned new changes in how to approach the methods and technology of the stations. Some stations need more maintenance than others, and they have had to figure out new ways on how to improve and standardize the program overall.

One of our favorite plants that thrives in foggy conditions is the Shaw’s Agave! This remarkable plant, which resembles a mix between a cactus and a succulent, can be observed in various locations throughout the park. Its thick, waxy leaves are specially adapted to collect moisture from the surrounding fog, efficiently directing this precious water to the base of the plant. This unique feature helps the Shaw’s Agave to survive in its environment, serving as a critical barrier to prevent water loss. (National Park Service). By utilizing the fog effective way, the Shaw’s Agave demonstrates an impressive example of how plants can adapt to and flourish in challenging conditions.

A large Shaw’s Agave plant.

Tracking Fog to Protect Cabrillo’s Plants

The data collected by the fog monitors is already helping scientists at Cabrillo National Monument have helped researchers understand the different patterns of fog and how different plants rely on it. They discovered that plants on the Bayside Trail get much less fog than those on the Oceanside Trail. Since fog is an important water source, tracking it helps scientists figure out the best ways to protect the plants. (National Park Service). With our environment changing quickly, this research is more important than ever to keep Cabrillo’s plants and ecosystem healthy!

About the Authors

Jupiter is a student interested in science who loves cats. Jacqueline is a student who enjoys learning about science and reading. Jupiter has been involved with CESAP since 2022 and Jacqueline has been involved with CESAP since 2024.

References:

iNaturalist. (2012, November 12). Shaw’s Agave.

https://www.inaturalist.org/guide_taxa/388015

National Park Service. (2024, August). Fog monitoring on the Point Loma Peninsula at Cabrillo National Monument: 2023 Annual Report. https://doi.org/10.36967/2305271

National Park Service. (2025, January 15). Innovative System Measures Fog That Beloved Plants Need to Thrive. https://www.nps.gov/articles/000/psv39n1_innovative-system-measures-fog-that-beloved-plants-need-to-thrive.htm

National Park Service. (2017, September 28). Fog Keeps Things Rolling. https://www.nps.gov/cabr/blogs/fog-keeps-things-rolling.htm