3 Parks 3 Stories

Of the diverse array of native plant species that call Cabrillo National Monument home, few are more conspicuous than Shaw’s agave (Agave ssp. shawii shawii). If you are lucky, you might catch the large rosette-shaped succulents in bloom — an occurrence that happens only once in their 30-40 year lifetime. With such a limited window for reproduction, pollination is a high-stakes game for these rare Mediterranean flora.

But who is pollinating the Shaw’s agave on the island-like swatch of land protected within the park boundary? Biologists at Cabrillo and the San Diego Natural History Museum (SDNHM) partnered to find out.

Historically, Shaw’s agave spanned the coast from southwestern California to northern Baja California, Mexico. North of the border, the species has been reduced to just two small and isolated populations as a result of heavy development. Thus, understanding the plant’s pollinators could be a key in restoring the US fragment of the species.

The large tubular and upright flowers of Shaw's agave demonstrate characteristics associated with chiropterophily, or bat pollination.

The specific pollinator of Shaw’s agave, however, has not yet been definitively identified. Scientists at Cabrillo and SDNHM have conducted extensive pollinator surveys using Anabats (specialized acoustic monitoring devices used to detect bats), in conjunction with remote video camera traps and in-situ observations.

This work has identified honey bees, hawk moths, and a variety of birds as the most common visitors to Shaw’s agave flowers; though no active and obvious pollen exchange has been observed.

In Baja California, nectar feeding bats such as the Mexican long-tongued bat (Choeronycteris mexicana), lesser long-nosed bat (Leptonycteris yerbabuenae), and pallid bat (Antrozous pallidus) are thought to be the natural pollinators of these plants. Though it is possible that bats may have visited the stands of Southern California agaves in the past, monitoring at the agave stands north of the US/Mexico border show no evidence of this.

Understanding the Data || Preserved collections from the San Diego Natural History Museum allow us to understand the historical ranges of many Southern California and Baja California plants and animals. To the right is a Mexican long-tongued bat specimen.

In 2024, Anabats stationed at Cabrillo picked up a Mexican long-tongued bat call - the first since the monitoring protocols began. A photographic siting of the bats feeding from agave flowers was also confirmed at a nearby locations in La Mesa, CA (photo above) and Escondido, CA. What this might mean for the northern population of Shaw’s agave is yet to be determined, but it is exciting to see the bats returning to these locales.

Understanding the Data | Since bat calls are at a frequency too high for the human ear to detect. Anabat devices are used to capture the calls. Each species can be identified by its unique call pattern. The pattern to the right is that of the Mexican long-tongued bat.

Black abalone (Haliotis cracherodii) are considered a keystone species in the rocky intertidal zone meaning they play a significant role in the health of the ecosystem. In addition to being ecologically valuable, historically the species is known to have been an important food source for humans. As our economy and ability to extract resources grew, black abalone populations began to dwindle. Still, given the species’ ability to prolifically reproduce, it was considered an inexhaustible resource. But that, unfortunately, turned out to be wrong.

In the late 1980s, a devastating disease called withering syndrome spread through the entire population, further reducing the population. By 1993, black abalone populations were so diminished that commercial and recreational fisheries were closed. In 2009, the US Fish and Wildlife Service listed black abalone on the endangered species list. Mainland populations were virtually non-existent and remain so today. However, in small pockets, black abalone populations hung on.

The isolation and protection of Channel Islands National Park provided a refuge for black abalone to weather the dual storm of over-exploitation and disease. The diminished populations of abalone slowly began to increase off the Channel Islands in the cold surrounding waters, which are known to limit the spread of withering foot syndrome.

Understanding the Data | While the population is far from where it used to be, we are now seeing the highest numbers of black abalone observed in many years—a good sign for the recovery of this critical intertidal species. In fact, there are enough abalone present that marine ecologists believe that we can begin moving small portions of the Channel Island’s population to the mainland where black abalone have been absent for decades.

In 2023, a team of scientists and managers from the National Oceanic and Atmospheric Administration, the National Park Service, The Nature Conservancy, California Department of Fish & Wildlife, the University of California-Santa Cruz, and the University of California - Santa Barbara began the work of safely transporting 115 black abalone from the Channel Islands to the mainland of Central California.

As of the Spring 2024 season, survival rates of the translocated abalone have been reported as high. Monitoring and tracking of this initial population will continue with a keen eye to observe if baby abalone are recruiting to the area – a sign of success. If all goes well, the team will conduct additional translocations to support stable and reproductively viable populations at key locations throughout California.

The Santa Monica Mountains National Recreation Area protects approximately 153,000 acres of Mediterranean coastal ecosystem. A habitat-type found in only five other locations around the world. Over 1,000 plant species representing 26 distinct natural communities flourish within the park boundary. In these mountains, the diversity of flora provides a rich and significant foundation to support a thriving ecology for both the human and animal inhabitants that call this region home.

Efforts to preserve the ecological legacy of the Santa Monica Mountains can take many different forms. For the past 20 years, plant specimens across the park have been collected, pressed, and preserved in unique libraries called herbariums. The plants in these collections provide a historical snapshot of the composition and diversity of this region. Scientists use the collections to better understand the impacts of our changing world, not just to these plant communities, but also for those that rely on them.

While herbariums are an incredible tool that shed light on historical changes to natural ecosystems, they are also subject to the consequences of these changes. In 2018, one of the Santa Monica Mountains herbarium collections was destroyed by the Woolsey Fire – a devastating event that impacted over 88% of park lands.

In total, 440 pressed plant specimens representing 439 different species were lost forever from the park’s archive. As the anthropogenic impacts of urbanization, habitat loss, and climate change increasingly threaten our natural, historical, and cultural resources, park managers are galvanized to adapt faster than ever before with novel and innovative conservation solutions.

There’s intrinsic value in these plants. Some of the plants in the herbarium are endangered species or have even gone extinct. They’re the only record in some cases... The herbarium provides invaluable information that we can use to better our world.

As the effort to rebuild the lost collection began, the resources team simultaneously initiated steps to safeguard the specimens from future calamity. Using a specialized digitization process developed specifically for herbarium collections, a high-resolution image of each pressing is taken and uploaded, along with its associated data, to the Consortium of California Herbaria. Not only does this process secure a majority of the data from another tragedy, but it also makes the collections more widely accessible for the public and for wider scientific application.

 _{Visit the Consortium of California Herbaria Digital Collections Here ||  cch2.org/portal/}