March 30, 2012
Looking at the Natural History of Santa Cruz Island
With the population in Los Angeles County fast approaching 10 million, it’s hard to imagine that just 19-25 miles off the Ventura coast, sits an unpopulated island of 96 square-miles that has remained in near pristine condition for thousands of years. As the largest of the Channel Islands, Santa Cruz is able to exist in such a preserved state largely due to it being positioned in one of the most biologically rich and productive marine regions in the Eastern Pacific – known as the Southern California Bight. Just south of Point Conception, portions of the southerly flowing California Current bend eastward towards shore into the Santa Barbara-Ventura Basin that separates the Northern Channel Islands from the mainland. There, this cold, nutrient-rich current converges with the warm, saline waters of the California Countercurrent as part of the larger ocean gyre system that’s created by the mixing of the California Current System around the Channel Islands. The combination of oceanic and climatic factors that make Santa Cruz so unique and rich in biodiversity have also helped lead to its protection and preservation, as 76% is owned by the Nature Conservancy, and the remaining 24% by the National Park Service.
Santa Cruz is not only the largest island, but it also has the highest peak (Picacho Diablo), which helps to create the many different microclimates on the island, also causing it to also have the greatest number of plant and animal species as well; 650 types of plants can be found here, and 480 of them are native to the island. The unique biogeography of the Southern California Bight has resulted in the Channel Islands being the exclusive home to 37 plant species; 8 of which are endemic to Santa Cruz alone, meaning they can be found nowhere else on the planet.
It is one thing to read descriptions of the natural history of Santa Cruz, but there is always a lot more to be gained personal experience and hands-on learning. Over the weekend, I was given the opportunity to camp at the field research station on Santa Cruz as part of a class field trip. The purpose of the trip was for observational analysis; it gave us a chance to visualize and discuss the relationships between the island’s many biogeographic characteristics, and to visualize concepts such as how variations in spatial distribution and types of vegetation are correlated to things like sun exposure and the gradient of the hillside. For example, in the following photo, you can distinctly see the how the concentration of vegetation increases as the gradient decreases and nears the low-lying center of the drainage basin – closer to the water table. 
The slopes of the more distant mountains on the left are much steeper and higher in elevation, causing rainfall to drain rapidly. The resulting smaller concentration of plants found here are likely to be better adapted for faster water absorption and longer retention. The lack of vegetation could also be the result of a rainshadow effect that results from the sharp rise in elevation forcing moisture flowing onshore to condense and precipitate in order to rise over the mountains. In the absence of strong onshore winds, the lower elevations and valleys retain more moisture as fog, which can further be correlated to the increase in the abundance of vegetation shown in the photo. The hills on the right have a smaller gradient at a lower elevation. These factors allow the plants to accumulate more water and lead to the growth of the more herbaceous vegetation.
With so many valleys and rapid changes in elevation across the island, there are many resulting microclimates that contribute to the overall high level of plant diversity. One of our goals of the trip was to identify some of the island’s native and rare endemic species as we hiked across different parts of the island. Of the ones we observed, 15 native samples were collected and placed into flower presses. In the photos below, you can see my personal favorites, the Giant Coreopsis, Coreopsis gigantean (top), and the Island Morning Glory Calystegia macrostegia (below).
One of the focus areas of the trip was to compare Catalina and Santa Cruz islands in terms of climate, plant and animal abundance and diversity, and comparing the anthropogenic effects of settlements on Catalina to the long-preserved state of Santa Cruz. For example, due to the increased grazing pressure on Catalina from introduced species like deer, buffalo, and cattle, some of the undergrowth tended to evolve upwards over time in order to be higher out of reach. On Santa Cruz, the lack of grazers is reflected in the more shrub-like and spread out orientation of some of the vegetation. Over time, the grazers also led to differences in the distribution of certain plant species on the islands. The Giant Coreopsis is a good example of this because it’s preferred by many grazers; it is found growing abundantly on Santa Cruz in many different microclimates, whereas on Catalina it is mostly found growing on coastal bluffs – out of reach of the grazers. One of the interesting things we learned involved the complex relationship between the eagles and native foxes, as well as populations of feral pigs and spotted skunks. While they are damaging to certain types of vegetation, the role of these introduced pigs on the islands evolved over time to play a key part of the recovery efforts of both Bald and Golden Eagles on the islands, and reduce the predation pressure on some of the recovering populations of native island foxes.
As part of the restoration program, nesting pairs of eagles have tagged and monitored, and recently it was discovered that two bald eagle chicks have been born in nests on Santa Cruz Island. It was also the earliest that eggs had ever been laid since recover efforts began, and as of Wednesday, March 7th, a record 15 breeding pairs of eagles are known to be living among the Channel Islands, showing that they are making a solid recovery. In order to monitor the progress of the nests and increase awareness of their conservation efforts, live footage of 4 of the nests can be streamed below. There are two nests on both Catalina and Santa Cruz, and what’s even more exciting is that the eggs in these nests are all within a couple weeks of hatching.
I believe that stories like these help to highlight the importance of keeping the Santa Cruz preserved in its most natural state for future generations to see and learn from. It was a great hands-on educational experience and allowed us the opportunity to see what the island may well have looked like thousands of years ago.
This post was authored by Genivieve McCormick ’12 who is pursuing a BS in Environmental Studies and Mabel Nevarez ’12 who is pursuing a BA in Environmental Studies.
External media sources:
http://www.channelislandsrestoration.com/sci/about_santa_cruz_island.htm
I wholeheartedly agree with the idea that “there is always a lot more to be gained personal experience and hands-on learning” at a location like Santa Cruz Island. It’s hard to imagine the variation in buckwheats or the difference grazing pressure can have without seeing them firsthand. I believe Santa Cruz has a good opportunity to be well managed into the future, with a tiny resident population, and two dedicated organizations trying to preserve various aspects of the islands unique character. However, I wonder how many people can be offered the type of hands on experience we were offered before it would affect the preservation effort. While Catalina has much more pressure from introduced species and a resident population on two parts of the island, about one million tourists visit the island. If anyone asked if they should visit the channel islands I would strongly recommend they visit Santa Cruz. But how long can the island maintain its character (especially near trails) as more visitors come to the island?
This past weekend we embarked on our second field trip of the semester! We had the pleasure of spending two nights and three days on the peaceful Santa Cruz Island Field Station managed by The Nature Conservancy. We observed the natural environment and took plant specimen for our plant presses.
My biggest take away from the weekend was comparing the vegetation from Santa Cruz Island to Catalina Island. Santa Cruz Island is home to many more trees and larger plants. It was lush and green and wet, compared to Catalina’s very Mediterranean climate and shrubbery. This difference in flora is due to multiple factors including biogeography, variety of animals present, climate, and geological history.
Biogeography states that larger islands and islands that are closer to the mainland will have high biodiversity. Santa Cruz Island is both large in area and closer to the mainland than Catalina Island, so biogeography makes sense. Unlike on Catalina, there is an absence of large grazing animals on Santa Cruz Island. This effects how the plants grow. For example, Giant Coreopsis only grows near cliff edges on Catalina because grazers don’t go near there. However, on Santa Cruz Island you see Coreopsis everywhere because grazers aren’t there to eat it all up. As for climate, Santa Cruz Island, especially the northern side, gets a lot more fog, which allows for more moisture and more greenery. Trees are able to catch fog on their leaves and let the fog drop down onto the ground for them to take in through their roots, as the researcher from UCSB who was there told me. And finally, the geological history adds diversity to Santa Cruz because this island was once very much a part of the mainland down near San Diego, and back then many animals and plants could have migrated onto the piece of land before it became an island.
Here is a video that shows some of the plants I learned about this weekend:
http://www.youtube.com/watch?v=RBiDX8od_AQ&feature=youtu.be
Citations:
All video footage was taken by me, Nina Gordon-Kirsch on March 23-25, 2012.
Info for blog post:
http://nrs.ucop.edu/reserves/santac_cruz_island/santa_cruz_island.htm
Info for plant ID:
Endemics: http://www.channelislandsrestoration.com/sci/endemics.htm
General plant listing: http://www-plb.ucdavis.edu/botanyclub/SC_Island/SCIPlantList.html
Dan brings up a very good point about how there’s only so much hands on learning that can be done before an area starts to be negatively affected. However, I think that one of the things that works in favor of Santa Cruz Island is that there it has very limited access. Being that there are no permanent settlements and few boats travelling to and from the island each week, it makes it easier for conservation efforts to keep up with the affects of what little human interaction there is with the island’s many natural habitats. Plus, the high costs associated with the travel to and from the island keep the number of visitors relatively low, and typically those willing to front the travel costs to get to the island are those who tend to care more about the environment and are less inclined to hinder preservation efforts. On the other hand, there does seem to exist a catch-22 between wanting to increase awareness and education of island ecology and conservation and wanting to keep anthropogenic pressures to a minimum on the island.
I really did appreciate this trip, and I do agree with you guys about the effectiveness of the “hands-on” experience. I personally really enjoyed seeing the differences in plant life between this island and Catalina and the diversity of microclimates. It is interesting how ecosystems with such similarities can have such distinctions as well. The elevation of Santa Cruz was something we were personally able to experience. Throughout the hike we were not only very conscious of the changing elevation, but we had to take notice of its effect on the distribution of plant life as we scoured the area for specimens for our plant press.
One of the guys made a funny comment about how excited some of the girls were about seeing all of the Coreopsis on Santa Cruz as compared to only seeing a few in the nursery on Catalina island. I do have to say though, taking the time to notice those things really helped the concept stick.
By visiting both islands the important of conservation and mitigating human impact was very strongly impressed on me. It’s so strange to think that such a beautiful locations can be threatened by so many things that humans do. Everything from the organisms we accidentally bring with us to the trails that we build can have a dramatic impact on such delicate ecosystems. Perhaps if more people were able to experience this island ecosystem themselves they would better understand how the actions of human development can affect so many of the natural wonders of this world.