March 30, 2012
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.
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