By Julie Cohen, UC Santa Barbara Public Affairs, and Kathleen M. Wong, UC Natural Reserve System
In order to plan for the future, sometimes you have to look to the past. More than two dozen scientists in disciplines ranging from anthropology to ornithology to history to geography did exactly that in a new study of California's Channel Islands.
The goal of the group, which hailed from roughly 20 different institutions, was to use historical ecology to demonstrate the importance of interdisciplinary research. Historical ecology studies analyze the interactions between humans and their environment over long periods of time, typically centuries. The scientists hoped to improve their understanding of long-term changes in Channel Island ecology and biodiversity to guide management of the ecosystem. Their results are published in the journal BioScience
The Channel Islands encompass eight land masses ranging from Catalina Island in the south to San Miguel Island in the north. The study examines 20,000 years on the islands from before human occupation through the arrival of Native American hunter-gatherers, commercial ranchers and fishers, the United States military, and other land managers.
An ideal model for historical ecology
“The trends show that we are moving into a period of climate change,” said Lyndal Laughrin, a coauthor of the study and director of Santa Cruz Island Reserve. “So how do we take the past and what the present is telling us and prepare for the future? I think it’s important that we are connecting the past to the future using a multidisciplinary outcome.”
Santa Cruz Island Reserve, administered by UC Santa Barbara, is one of 39 reserves in the 756,00-acre University of California Natural Reserve System. Santa Cruz is the largest of the Channel Islands and is co-owned by the National Park Service and The Nature Conservancy.
“The distant past had a whole different regime with larger islands due to a lower sea level and more forestation as a result of a cooler climate,” Laughrin added. “The more recent historical past was influenced by agriculture and ranching, which changed the islands, and now the changeover from private ownership as well as economic pressures have turned the focus to conservation and restoration efforts.”
Because of their relative isolation, the islands were an ideal model for the study. While the Channel Islands are not as remote as Hawaii or the Galápagos, they are nonetheless home to a number of endemic species found nowhere else.
Endemics occur in two different ways. Some are the result of species surviving on the islands but dying out elsewhere, typically victims of climate change and loss of habitat. Others are species that ceased interbreeding with their parent populations and evolved on a separate trajectory.
Today, endemic island mammal subspecies are found on the Channel Islands, including the spotted skunk of Santa Cruz and Santa Rosa islands and six different subspecies of island fox found on all of the Channel Islands save Anacapa and Santa Barbara. Of the 271 endemic plant taxa, 44 are single-island endemics and 37 are endemic to the four northern islands—Anacapa, Santa Cruz, Santa Rosa and San Miguel.
The researchers found that, in addition to this natural selection process, climate change and human disturbances have contributed to present degradation of Channel Island ecosystems. While the need for restoration is clear, the best way to achieve healthier island ecosystems are not.
Shaping the islands of tomorrow
The best way to guide conservation management, argue the researchers, is to reconstruct past environmental conditions, and examine how these have evolved with shifts in climate and human usage. With this approach, the scientists discovered that rising sea levels produced an estuary teeming with shellfish that no longer exists today; that early inhabitants likely translocated foxes from island to island for centuries, diluting their genetics; and that islands once covered in forest became mosaics of grassland, shrubland, and woodland due to ancient climate changes. Having a detailed view of how the ecosystem is connected, and how it may respond, can give land managers a clearer view of how their projects might impact the islands.
“The strength of this research is the idea of how this whole interaction between the natural world and the human world is built on the past,” Laughrin concluded. “Our job now as conservationists is to combine what we have now with what we need to do, incorporating an increasing human population and anticipated climatic change.”