Gully Erosion: ~100,000 m 3. Wave Erosion: ~1,000,000 m 3. Coastal Erosion August 2008 – June 2009. EROSION MITIGATED RECOVERY OF KASATOCHI ISLAND NESTING AREAS, 2008-2011. DISSCUSSION As long as wave erosion remains the primary
Wave Erosion: ~1,000,000 m3
Coastal ErosionAugust 2008 – June 2009
Approximate extent of 2008
(Photo courtesy of Burke Mees, Sept. 8, 2011)
Gary S. Drew1, Chris F. Waythomas1, Jeff F. Williams2, and John F. Piatt1, 1 USGS Alaska Science Center, 4210 University Drive, Anchorage, Alaska, 2U.S. Fish and Wildlife Service , Alaska Maritime Wildlife Refuge, 95 Sterling Highway, Homer AK
Fig. 3. Erosion by wave action here has regressed the coastline 300-400 m in less than one year.
Pre-eruption Nesting Areas1996-2008
The magnitude, type, and sometimes-prolonged nature of volcanic activity in the Aleutian Islands have shaped the habitats and behavior of the species that use them. Kasatochi volcano, in the Central Aleutians, erupted explosively on August 7–8, 2008 completely burying all terrestrial habitats with pyroclastic deposits tens of meters thick. These deposits filled and covered rocky crevices in boulder and talus fields used by the estimated 500,000 seabirds, predominantly Crested Auklets (Aethiacristatella) and Least Auklets (Aethiapusilla), that nested on the island prior to the 2008 eruption. The strong colony fidelity of these two species (Sealy 1975, Jones 1993, Drew et al. 2010) suggests that these species must be adapted to the periodic disturbance regimes that dominate the Aleutian Islands. We examined the role of erosion as the primary recovery mechanism for crevice nesting species on Kasatochi Island 2009-2011.
Figure 2. Time-lapse cameras installed above Tundering Cove.
Figure 4. Gullies have expanded with the deepest gullys reaching approximately 30 m deep, but have provide little or no new access to nesting habitat.
Figure 3. Depiction of coastal changes 2008-2011, based on satellite imagery.
Figure 1. Location of Kasatochi, Ulak and Koniuji Islands, Alaska. The volcano lies approximately 1900 km west of Anchorage in the western Aleutians. Red lines represent the at-sea survey tracks for seabirds during July of 1996 and 2003, and June of 2009.
Figure 6. Bolder pile in Tundering Cove where Least auklet nestlings were found in August 2011.
Figure 5. Time sequence of shoreline erosion and beach bolder build-up on the north-west side of Kasatochi . The pre-eruption “Tundering Talus” colony site is further upslope outside the image frame..
Figure 7. Base of a gully on the South side of Kasatochi June 2011. The deepest gullys are approximately 30 m deep.
The large amount of material deposited on Kasatochi by the 2008 eruption effectively eliminated all crevice nesting habitat on the Island. However, the rapid removal of volcanic material allowed both Crested and Least Auklets to attempt nesting within two years. Crested and Least Auklets have demonstrated a behavioral flexibility, making use of ephemeral and often low quality nesting habitat. While we expect the upward reproductive trend to continue, this exponential rate of increase is likely to level off. Although we estimate that that the number of fledged birds reached between one to several thousand(s) in 2011, it is unlikely that this level of reproduction will be sufficient to offset mortality of the breeding population that has had no significant recruitment since 2008. At-sea surveys will be conducted in 2012 to identify any changes in density based on previous surveys in 1996, 2003 and 2009 (Drew et al. 2010).
Figure 6. One location of nesting habitat identified August 2011. Most pre-eruption nesting occurred approximately 100 m upslope, to the right.
Drew, G. S., Dragoo, D. E., Renner, M., and Piatt, J. F., 2010. At sea observations of marine birds and their habitats before and after the 2008 eruption of Kasatochi Volcano, Alaska. Arctic, Antarctic, and Alpine Research, 42: 325–334
Jones, I. L., 1993: Crested auklet (Aethia cristatella). The Birds of North America, No. 70. Philadelphia: The Academy of Natural Sciences.
Sealy, S. G., 1975. Influence of snow on egg-laying in auklets. Auk, 92: 528–538.
Waythomas, C.F., Scott, W.E., and Nye, C.J., 2010, The geomorphology of an Aleutian volcano following a major eruption: the 7-8 August 2008 eruption of Kasatochi Volcano, Alaska, and its aftermath: Arctic, Antarctic, and Alpine Research, v. 42, n. 3, p. 260-275, doi:10.1657/1938-4246-42.3.260.
Figure 8. Least auklet nestling in Tundering Cove, August 2011.
Fig. 7. Available nesting habitat sequence from pre-eruption through 2011. The background image was collected in April 2009. The yellow line represents the pre-eruption coastline. The areas in red represent nesting areas .
ACKNOWLEDGMENTS - This work would not have been possible without the past and continuing support of the U.S. Fish and Wildlife Alaska Maritime National Wildlife Refuge. We especially thank Vernon Byrd, and the crew of the M/VTîglax for their commitment to this work. We thank the North Pacific Research Board, U.S. Fish and Wildlife Service and U.S. Geological Survey for providing funding for the post-eruption research.