USC Dana and David Dornsife College of Letters, Arts & Sciences > Blog

April 20, 2012

A comparison between Catalina and Santa Cruz Islands

Filed under: Catalina Island,Santa Cruz Island — admin @ 9:01 pm

One characteristic shared by the two islands is how susceptible their ecosystems are to disturbance, as exhibited by the crashes of their island fox population.  Although different in cause, each demonstrated that a small island ecosystem, evolving under sheltered protection from mainland disturbances can create unique and fragile ecosystems that do not handle major disturbances well.  This is largely due to their relatively small gene pool of the population and small geographic range.


Island Fox

In other more traditional geographic regions, a disturbance in an ecosystem that leads to a population crash can often be followed by an easier recovery.  Either there is a large enough, well-adapted surviving population that can repopulate, or organisms from another region can gradually be reintroduced into the area.  However on an island, often neither is possible. If the species experiencing the crash is endemic, then it is possible that the crash will result in the species extinction as no other existing members of the species exist in the world.  Even if some individuals survive the initial disturbance, with the population, small to begin with, may leave so few survivors that the gene pool does not carry enough diversity for a proper recovery and the species may die out.  As such, a disturbance in an island ecosystem is much more likely to lead to species extinction.
On Catalina Island, the collapse of the fox population was primarily due to the introduction of the canine distemper virus.  In 1999 an outbreak occurred causing the population to drop from 1300 to only 100 animals.  The outbreak swept across the west side of the island but fortunately did not reach the eastern island, which was separated by a narrow isthmus.  In 2000 the Catalina Island Conservancy and the Institute for Wildlife Studies instituted the Catalina Island Fox Recovery Plan, which consisted of monitoring, captive breeding, vaccination, and relocation of the foxes.  The program was a success and by 2004, the population had climbed up to 300.  Although it is not entirely known how the virus was introduced into the population, one theory is that it was brought to the island by an infected domesticated dog or a stow-away raccoon.

Feral Pig

On Santa Cruz Island, a collapse also occurred, but for different reasons.  Over-predation by the golden eagle, an exotic species, was discovered to be the primary cause.  However indirect blame could be placed on the human introduction of pigs to the island.  A study by Roemer et. al. indicated that the colonization of Golden Eagles onto the island could only be sustained by the existence of a feral pig population.  However, even though the foxes alone could not sustain the eagle population, they were much more affected by eagle predation than the pigs.  The foxes were ill adapted to evade eagle predation and as such faced possible extinction.


Golden Eagle

Like the island fox’s unfortunate fate at the hands or claws of introduced species and viruses, many native and endemic plant species on both Catalina and Santa Cruz islands have suffered from human introduced grazers. While both islands have gone under some form of plant restoration from the damages done by past-introduced grazers, Catalina currently still has resident populations of non-native grazers while Santa Cruz Island does not. This provides an interesting contrast between the islands because there are many similar native plant species that exists on both islands but in different quantities and manifestations. Through this comparison one can clearly see the tremendous impact that grazers have on the plant communities of the Channel Islands.


Catalina Island Bison

Catalina currently has a small population of 150-200 bison that roam the island. The bison population is controlled both by a birth control that limits the number of calves a female bison can have a year and by shipping the bison back to the mainland to supplement mainland herds on tribal lands. The birth control method was introduced in 2009 and was greeted by animal rights activists who opposed the Catalina Conservancy’s earlier eradiation of feral goats and pigs with high power rifles from helicopters. The Los Angeles Times reported that the birth control option for controlling the bison herds was suggested by an animal activist Avalon shop owner named, Debbie Avellana. Other non-native grazers that continue to roam the island are mule deer that are kept under control by recreational hunting as well as the Conservancy, and a very small population of black buck antelope. Historically Catalina was used for grazing goats, pigs, sheep and cattle but have since been irradiated.
Catalina’s current native plant population has suffered as a result of the current non-native grazers on the island. The effect of the grazers can be seen all too clearly in the example of the native Giant Coreopsis (Coreopsis gigantea). On Catalina this “Dr Seuss plant” is only found with in the confines of the Ackerman Nursery where grazers are kept out. There are also reports of some wild species on the sea bluffs or steep gullies of the island where grazers can’t get to them. On a whole plants on Catalina tend to be bush-like where they otherwise would be more like trees. The only “trees” you will find on Catalina are either non-native or are the native toyon, lemonade berry, sugar bush or Catalina Cherry trees because they are so resilient. Some native plants have changed their pollination season to try and outcompete not only the grazers but also invasive plants.
Restoration on Catalina is difficult because there is a permanent human population there and the island attracts around a million tourists a year. This constant stream of visitors means the potential for foreign species introduction is more likely. Fennel is still a problem on the island being an aggressive invasive species, but a management strategy including weeding around campsites and populated areas outward seems to be working in its early stages. Another invasive species is the eucalyptus, which was brought to the island on purpose to beautify areas like Avalon and was a favorite of the Wrigleys. Santa Cruz Island also struggles with both eucalyptus and fennel.

Tourists in Avalon

Santa Cruz Island does not have any non-native grazers currently living on the island. Historically Santa Cruz Island was a ranch raising some of the most well known beef and sheep products on the west coast. Since then it has been brought under the control of National Park Services and the Nature Conservancy. The only human presence is that of campers and eco-tourists, and researchers. There are a few people that live there to maintain the research and historic ranch facilities. These conditions have allowed a recovery of many native plants and allows for these plants to grow large and where on Catalina you may have a sparse bush, on Santa Cruz Island you will have a large bush as tall as a man. On Santa Cruz Island, Giant Coreopsis and Bedstraw are significantly more common than on Catalina as are buckwheats (including one species of buckwheat that is endemic to Santa Cruz Island), Manzanita (also including a endemic species), and Sunflower bush. Santa Cruz Island has around 600 native plant species.

Santa Cruz Island Landscape

These cases, exhibit how island ecosystems are incredibly susceptible to disturbances, which can often be brought upon by the interference of humans.  In the case of Catalina Island Fox, the introduction of a virus, possibly by a colonizer’s pet dog, is to blame for the collapse of a species.  Santa Cruz’s population collapse was brought upon by the human introduction of pigs to the island, which facilitated the entry of yet another harmful invasive species.  It is believed that in both instances, had humans not brought in these disturbances that such a collapse would not have occurred.  Just as these collapses wouldn’t have occurred without human interference one can use Santa Cruz Island to “see” how different a landscape Catalina would have if it didn’t have the human introduced grazers still shaping plant communities on the island. As such these cases serve as a reminder that humans should exercise extreme caution when interacting with such isolated ecosystems, as they can be as fragile as they are unique and beautiful.

This post was written by Mariah Gill ’12 and Jefferey Nakashioya ’12 both seniors in Environmental Studies.

Carlos de la Rosa, Personal Communication/ Lecture

February 2, 2012

Catalina Island Field Trip- January 27-28, 2012

Filed under: Catalina Island — admin @ 12:18 am

I just returned from an awesome field trip to Catalina Island. My ENST 495 classmates and I had the privilege of spending Friday and Saturday on the island learning first hand what we went over in class the past three weeks: Catalina natural history, fires in the wild, and Marine Protected Areas.

My favorite part of the weekend was an assignment to collect 15 plant specimens, identify them, and put them into a plant press. I not only learned about native and non-native species, but I am also now able to point out which plant species are endemic to Catalina.

I made a little video about some of the plants:ENST 495 Catalina Video

I think the coolest thing I learned was about why many of the plants have little hairs, or fuzz on them. This is to shade themselves from the sun. Catalina has a Mediterranean climate, which means very dry, and little rain. Therefore, the plants need to keep in moisture as much as possible, so with hairs that provide shade, the plants release less water into the atmosphere because their surrounding temperature is a little bit lower. That is SO COOL!

And to top it off, we got to go snorkeling!

Amelia Bahr & Nina Gordon-Kirsch geared up for snorkeling

This post was authored by Nina Gordon-Kirsch ’12 an Environmental Studies major (BS) with a minor in marketing.

January 26, 2012

Marine Protected Areas

Filed under: Catalina Island,Marine Protected Areas — admin @ 8:32 pm

Marine Protected Areas (MPAs) are government-protected regions in which human activity is regulated in order to preserve both marine resources and their unique ecosystems. Through different types of management programs and restriction strategies, government and local communities collaborate in order to protect threatened marine biodiversity and landscapes. Although MPAs may differ substantially in their size, location, and level of restriction, the majority of MPAs are established within territorial waters where enforcement can be ensured.

There are a variety of management approaches utilized by government in order to rehabilitate threated marine ecosystems.  The least prevalent—occurring in less than 1 percent of all United States’ waters—are “no-take” zones, areas where fishing is not allowed.  Other more common restrictions are ship transit regulated areas and areas of no oil and gas mining. “Seasonal and Temporary Management” restricts fishing seasonally in order to allow fish populations to recover from harvesting, common during the spawning season of over-extracted fish species.  Because MPAs are difficult to enforce, communities participate in their protection by managing and imposing restrictions, either independently or jointly with the government. Because they are aimed at addressing ecological and socio-economic needs, in return, they positively influence the communities supporting them.

MPAs are widely recognized as a successful method for not only preventing further marine habitat degradation, but also, for the recovery of targeted fish populations. By limiting access to protected areas, the stress placed on local marine populations— due to fishing and other industry—is substantially reduced. Thus, mortality rates are reduced, which results in the survival and establishment of targeted species’ populations. While perhaps the biomass increase of targeted species might be most noticeable within the boundaries of the MPA, another effect, the ‘spillover effect’, has been shown to boost fish stocks in the areas surrounding MPAs. When localized overpopulation of certain species within the MPA occurs, individuals within fish populations leave the MPA in search of a less competitive environment. This exodus provides a steady stock of fish for fishermen operating outside the MPA. Recent research indicates that the spillover effect also applies to larvae, which drifts with ocean currents to surrounding areas. As a result of this migration, MPAs are designed into networks, which are aimed at establishing fish populations over a large area.

Despite the weight of scientific evidence supporting the benefits of MPAs, certain stakeholders still criticize and oppose the establishment of additional MPAs. The local fishing industry frequently opposes the development of MPAs due to potential restrictions that may limit their access to profitable fishing grounds. This is a natural concern, particularly if local fishermen do not understand the potential benefits of MPAs—increased catches of fish and larger game fish due to the spill over effect.  Other major stakeholders, representatives of the shipping industry, argue that certain MPAs restrict the flow of commercial and other various types of shipping vessels, which in turn cost companies money. In addition, oil and gas officials, argue that restrictions prevent them from pursing untapped oil and gas reserves that exist within restricted areas. Finally, the establishment of MPAs might infringe on the rights of indigenous peoples to extract resources from protected areas.

In the beginning of the decade, Marine Protected Areas came to the forefront of many international assemblies.  In order to draw attention toward the issue, the World Summit on Sustainable Development (2002), The Evian Agreement (2003), and United Nations Framework Convention of Climate Change (2004) set goals of establishing marine networks by 2012.  Although these goals were criticized as vague and ultimately unenforceable, they highlighted the importance of MPAs in order to mitigate recent marine biodiversity loss on a global, regional, and national scale.  In effect, many nations, including the United States, pledged to establish them.

In 1999, California passed the Marine Life Protection Act.  A part of the California Fish and Game Code, the Marine Life Protection Act requires MPAs to be established into a network by 2011.  Designed by a team of public advisers—the Blue Ribbon Task Force, a group of 7 public policy leaders nominated by the California National Recourse Agency— stakeholders and scientific advisory groups, MPAs and networks are created based on scientific case studies and statistical analysis.  California’s statewide MPA network is divided into five regional networks—the north coast network, San Francisco Bay network, north central coast network, central coast network, and the south coast network— which are strategically linked together. Initiated in September of 2007 and projected to be completed in 2012, the California MPA network consists of more than 18% of California’s state marine waters. Within the Los Angeles County, a part of the south coast network, there are thirteen MPAs, with nine MPAs surrounding Catalina Island. Evaluated based on adequacy, representability, resilience, and connectivity, these MPAs are constantly being monitored and evaluated in order to improve and gain more information on trends of ecosystem rehabilitation.

Despite an increased awareness towards marine biodiversity and its habitat, there still exist many at-risk marine environments internationally.  Because international waters are nearly impossible to monitor and enforce, there remains a huge inconsistency between international and national efforts towards marine protection and rehabilitation.  With constantly changing marine ecosystems, due to over extraction, pollution and global warming, marine biodiversity and marine habitats are projected to only deteriorate further.  However, scientists and conservation workers are suggesting an international network of MPAs—a web of interconnecting “breeding grounds”, aimed at feeding biodiversity to fisheries and the marine ecosystem on an international scale.   Although this might not be politically feasible in the near future, scientific evidence indicates that if this feat can be accomplished, it would positively impact on both the marine environment and those individuals who are economically dependent on the ocean for their survival.

Additional References:

National Marine Protected Area Center.

NOAA’s National Ocean Service: Marine Protected Areas.

California Department of Fish & Game, Marine Life Protection Act.

Marine protected area.

This post was authored by Michalea McLoughlin, a senior Environmental Studies major (BA); and Nick Horsburgh, a senior double majoring in Environmental Studies (BA) and Psychology (BA)

January 13, 2012

Natural History of Catalina Island

Filed under: Catalina Island — admin @ 10:45 pm

The Channel Islands are a chain of eight islands in Southern California off the Santa Barbara Channel.  Santa Catalina Island – often referred to as just “Catalina” – is located roughly 20 miles directly opposite Torrance and Palos Verdes and is one of the larger islands in the Channel Island chain (76 sq. mi.).  Catalina exhibits a mild, sub-tropical climate year-round and is composed mainly of a quartz base.  The vegetation resembles that of a desert/ chaparral climate, and noteworthy landmarks include Echo Lake and Black Jack Mountain.

California Channel Islands, from Wikipedia

Catalina is an oceanic island that was formed by tectonic activity as opposed to being a continental island that separated from the mainland many years ago.  This marine history was proved by the presence of fossils from plankton skeleton called diatoms.  The material created by the presence of diatoms, called diatomite, is white and looks somewhat chalky.  Continental islands’ native species often evolved from ancestral species that occupied the land before it broke away from the mainland, but oceanic islands are populated by immigrating species.  Catalina Island is relatively close to the mainland, and the island’s biodiversity reflects this proximity.  This follows the theory that larger islands will have higher levels of biodiversity than smaller islands, and islands that are closer to the mainland will have higher levels of biodiversity than those that are far away.  Over time, animals have rafted, flew, and swam across the channel to the island to populate Catalina and the other islands.  Once there, many have evolved to adapt to their new habitats.

Geological records are not necessarily conclusive, but it is possible to estimate species’ introduction to the island via remains and chart their arrival and extinction.  Additionally, researchers have noticed that many plant and animal species closely resembled species on the mainland, but their physical appearances differ slightly.  When species are separated from the mainland, and competitors or predators are removed, different physical traits may be selected over features that proved successful previously.

There are varying theories regarding the means of transportation taken by founder species and the reasons that species have changed in physical appearance.  The Island Fox, a species on six of the eight Channel Islands, is thought to have been introduced thousands of years ago when Native Americans brought them over as domesticated pets.

Island Fox, Photo: L. Collins

Present day feral cats and dogs were also introduced as pets, but are now wild.  More recent introductions, such as the Bison, have persisted on Catalina and have adapted to island life by evolving into ‘dwarf bison.’  The origin of the bison on Catalina is a funny one. In the 1920s, fourteen bison were brought to Catalina for the filming of a movie. After the movie was finished, the crew left the bison on the Island and their population grew quickly, now amounting to almost 600 across the whole Island.

Bison on Catalina Island, Photo: L.Collins

The island fox also exhibits a similar case to the bison of dwarfism and appears smaller than the average mainland fox.  The quail and squirrel, on the other hand, have become larger, exhibiting signs of gigantism.  It has been proposed that some smaller animals were able to grow larger over generations due to the lack of stress presented by predators and competitors, while once-large animals became smaller because there were not sufficient resources to keep them well nourished.  In addition, due to differences in environment and competition, some shrubs undergo ‘arborescence,’ which leads them to look more like trees after many generations.  On Catalina, this is true of the Toyon and Island Scrub Oak.  Species that can only be found in one place or region are called ‘endemic species,’ and Catalina Island contains eight such plant species and eight animal species as well as eight species of invertebrates.  According to the Catalina Conservancy, which managed 88% of the island, two of the plant species are still under review regarding whether or not they are truly endemic. An interesting case study is that of the Island Ironwood trees.  Many island endemics are often grouped as subspecies of mainland plants, but the Island Ironwood is the only species that is actually differentiated on the genus level from the parent species.  The Santa Catalina Ironwood (Lyonothamnus floribundus, floribundus) differentiates from the Island Ironwood (Lyonothamnus floribundus, aspleniifolius) in that the Catalina Ironwoods have significantly longer and wider leaves.

This post was authored by Nina Gordon-Kirsch ’12 an Environmental Studies major (BS) with a minor in marketing; and Annie Guo ’12 an Environmental Studies major (BS) with a minor in International Relations.

For more information about Santa Catalina Island, feel free to visit the Catalina Island Conservancy’s website.

Endemic Species as a part of the Natural History of Santa Catalina Island

Filed under: Catalina Island — admin @ 10:34 pm

Santa Catalina Island, as well as the other Channel Islands, off the coast of California exhibits unique, or endemic, biodiversity that makes it a place of interest for study by scientists.  Due to its consistent isolation from the mainland, species that have colonized Santa Catalina Island have evolved into distinct counterparts to their mainland relatives making them endemic.  These species originally have come to the island by various means such as the deposition of seeds of mainland plant species by flying birds or the “rafting” of animals on vegetative debris washed out to sea from mainland floods.  However, these endemic species have been threatened more recently by invasive species that have been brought by human activity.  Mitigation efforts have had moderate success although many native species have already been lost.

One particular example of a species endemic to Santa Catalina Island is the Santa Catalina Ground Squirrel.  The Santa Catalina Ground Squirrel is differentiated from its mainland counterpart by being noticeably larger.  Biologists have characterized the larger size of the endemic species as ‘gigantism.’ Gigantism is a common evolutionary trait for smaller vertebrate and many plant species that colonize islands.  Due to the lack of competition and predators on islands in comparison to the mainland, it is hypothesized that these organisms are able to evolve into larger forms of their mainland counterparts.

The Santa Catalina Ground Squirrel is endemic only to Santa Catalina Island causing it to be an interesting species to study for biologists and biogeographers.  Schoenherr, Feldmeth, and Emerson in their book, Natural History of Islands of California, state that it is not currently known why the Santa Catalina Ground Squirrel has not colonized the other Channel Islands as many other species have done.  Rafting on vegetative debris from the mainland is one possible explanation for how the endemic squirrels arrived on Santa Catalina although it would seem just as likely that the Santa Catalina Ground Squirrel would over time have rafted to and colonized other Channel Islands.  Schoenherr, Feldmeth, and Emerson suggest that due to evidence of the squirrel in Native American stool deposits on the island that they may have been brought to Santa Catalina for food.  Again, it is not fully understood why Native Americans would not have brought the squirrels to other islands for this same purpose.  One hypothesis for their endemism to only Santa Catalina may be that the island has remained isolated by the sea from its neighbors. This is different than the Northern Channel Islands that conglomerated into one larger island in glacial periods when sea levels were much lower than they are today.  The land bridges formed between what are individual islands today would have allowed species from those islands to intermix and colonize the larger landmass that subsequently was broken up when sea levels rose again.

One species that underwent further evolutionary differentiation due to the isolation of individual populations on separated Northern Channel Islands is the Island Fox. The Island Fox is present on most of the Channel Islands, with the subspecies of the Santa Catalina Island Fox being specifically endemic to Santa Catalina Island. Notably, the Island Fox has differentiated more than any other island mammal. It is closely related, however, to the nearby mainland’s Gray Fox. The Santa Catalina Island Fox is much smaller than its mainland relative representing a common evolutionary trait for larger vertebrates that colonize islands called ‘Dwarfism.’  Large animals’ tendency to be smaller when isolated on an island is attributed to the limited supply of food on islands as opposed to the mainland. However, it is not completely certain that the Gray Fox is the Santa Catalina Island Fox’s most direct ancestor as there is some dispute about how the Island Fox arrived at Santa Catalina Island.

Based on mitochondrial evidence and other scientific indicators, it is estimated the Island Fox’s common ancestor arrived to the Northern Channel Islands 16,000 years ago.  How the fox arrived at the Channel Islands, and more specifically Santa Catalina Island, is not known for certain, but evidence has indicated several possible methods. The vicariant distribution hypothesis is supported by the close relation between the Island Fox to three small fox species of the Yucatan region of Mexico and in Guatemala. Vicariant distribution relies on plate tectonics and the concept of a “land raft.”  About 29 million years ago, the Pacific plate and the North American plate, which meet on the west coast of North America, changed in their interaction from a head-on convergence to sideways motion also known as a transform system. The Pacific plate carrying the Channel Islands traveled north, breaking from near Sonora, Mexico, and brought the islands’ inhabitants with them acting as a “land raft.” Some suggest that when the plates shifted and caused the formation of the Channel Islands, the foxes came with the land.  As mitochondrial evidence suggests a much more recent colonization by the fox, this hypothesis is not as well supported.  Others suggest that the foxes may have come to the Channel Islands when sea level was low enough to make rafting on vegetative debris from the mainland.  However, the more widely held belief is that Native Americans who may have used the foxes as pets brought the fox to the Northern Channel Islands and Santa Catalina around 16,000 years ago.

The Santa Catalina Island Fox and Ground Squirrel are among the endemic species that are threatened by exotic species brought more recently to the island in the last few centuries. As Spanish missionaries settled California in the late eighteenth century, many domesticated animals like pigs and goats were introduced to the Channel Islands.  Invasive species quickly disrupted the ecological balance of the islands by destroying vegetation and competing with the native island species. Invasive plants took up valuable nutrients, water, and space from native shrubs. Pigs and hogs, rooting in the ground for food, exposed large amounts topsoil that was soon eroded into the sea causing a loss of fertility in the soil.  Goats, being indiscriminant eaters, ate vegetation so close to the ground that it was unable to recover.

Another invasive species, bison, was introduced to Santa Catalina Island not by settlers but by moviemakers. In 1924, bison were introduced to the island for the filming of the movie The Vanishing American. While bison populations have caused harm by eating and trampling native grasses, bison populations are now limited and graze on mostly introduced grasses preserving the natural plants of Catalina.  Also, the bison do not eat the vegetation as close to the ground as goats allowing for the vegetation to recover to a greater degree.

However, the negative impacts of these invasive species and human activities has not been able to rid the Channel Islands, and particularly Santa Catalina Island, of its fascinating and rich natural history and biodiversity. While some hypotheses suggest that the Santa Catalina Fox and Ground Squirrel were brought to the island by humans and therefore may be considered invasive, they have undergone thousands of years of evolution to become distinct species. Mitigation, conservation, and preservation efforts have been put in place and have had success. The Endangered Species Act has protected many of the endemic species of the island for years. In 1975, 42,135 acres, or 86 percent, of Santa Catalina was given over to the Catalina Conservancy for protection and management.  In 1989, efforts to rid Santa Catalina Island of the Feral Hogs and goats began including shooting or trapping the animals from helicopters and creating a sadly unsuccessful goat adoption program on the mainland. Today, it is estimated that there are less than 1000 goats, 3000 pigs, and 500 bison on the island with the western side of the island almost totally free of the destructive animals.  Regardless, many species unique to Santa Catalina Island regrettably have become endangered, or gone extinct, as their habitats are destroyed or taken over by invasive plants and animals. While Santa Catalina and the other Channel Islands provide great places to study endemic species and evolution, they also provide opportunities to study the management of invasive species, and conservation and preservation efforts that informs the work of others around the world combating these global problems.

This post was written by Brian Rodysill ’12, who is pursuing a BA in Environmental Studies with a minor in Natural Sciences; and by Alice Hall-Partyka ’14 who is pursuing a double major in Environmental Studies (BA) and Global Health.