Study Area
The Channel Islands have a coastal Mediterranean climate with rainy
winters and dry summers and are made up of rocky coasts, grasslands,
shrublands, and woody forests . The islands have historically been
subject to disruption, principally by humans, through the introduction
of livestock and other invasive animal and plant species. This in turn
has heavily impacted native flora and fauna communities on the islands.
Santa Cruz Island (250 km2, largest of the Channel
Islands) and Santa Rosa Island (215 km2, second
largest) are part of the northern Channel Island archipelago and
separated by a 9.6 km wide channel. The two islands were once connected
as a super island called Santarosae that was separated from the mainland
until sea level rise separated them from one another approximately
10,000 years ago after the end of the Pleistocene epoch . Santa Cruz
Island (SCZ) is characterized by two east-west mountain ranges that
bound a central valley, and hosts a variety of habitat types including
grassland, chaparral, coastal sage scrub, oak woodland, and pine forests
. Santa Rosa Island (SRI) is characterized by a single mountain chain
running east-west through the middle of the island, with relatively flat
marine terraces bisected by canyons and dominated by grassland on the
north side, and more rugged terrain dominated by sagebrush scrub on the
south side. Small pockets of native island oak and pine woodland are
present. Both islands support a number of similar habitat types;
however, Santa Rosa Island is less rugged and less topographically and
vegetatively diverse compared to Santa Cruz Island. Grazing livestock
were removed from most of Santa Cruz Island by the late 1980s, while
grazers persisted on Santa Rosa Island until 2011. Thus, the majority of
Santa Cruz Island is further advanced in vegetative recovery than Santa
Rosa Island.