Lonely Rocks and Atolls

Revisiting Island Evolution

Static Snapshot:

Current atolls and pinnacles reflect final stages of dynamic erosional decay of volcanic shield islands Shape and area a function of: - Subsidence - Erosion - Sea-level

Change

(Price & Clague 2002)

Revisiting Island Biogeography Dynamic Change:

Island overall elevation and size decrease with age Frequency of volcano formation has increased recently (<5 MY), decreasing the spacing of islands How do these patterns affect biogeography? (Price & Clague 2002)

List of Geological and Benthic Habitats

What do I want you to know about these features? - Sequence (SE to NW) *** NOT Lat / Long ***

- Age - MY (from Clague 1996)

- Five types of features: bank closed atoll open atoll basalt island / sea stacks carbonate island

List of Geological Features

Depth < 20m

Ikonos Imagery

Nihoa Island is located 250 km northwest of Kauai, the closest to the Main Hawaiian Islands Nihoa if the largest and the tallest emergent island in the NWHI, reaching an elevation of 275 m at Miller Peak Geologically youngest island at 7.3 Million Years of age Deeply eroded remnant of a once large volcano and basaltic shelf

Landing on Nihoa

Island measures about 1,500 yards east and west by 300 to 1,000 yards wide. It can be compared only to half a saddle as the northern side drops off in a nearly perpendicular cliff. Cliff is 360 feet high in the middle of the island; but reaches a height of over 800 feet on the two ends. Southern side of island is also a cliff, with two small landing coves. No helicopter landing sites.

Habitats on Nihoa

Nihoa – Endemic Plants

Home to 25 species of endemic plants and several land animals, making it the most diverse island in entire NWHI

Pritchardia remota Nihoa Fan Palm or Louʻlu 1885 fire ravaged island. 700 remain. Endangered

Amaranthus brownii an annual herb growing on rocky outcrops at

altitudes of 120–215 m. Critically Endangered

Schiedea verticillata Nihoa Carnation.

Endangered

Nihoa – Land Endemic Animals

Two endangered endemic land birds: Nihoa finch (Telespyza ultima) Nihoa millerbird (Acrocephalus familiaris kingi)

Nihoa – Seabirds

Nihoa island - Bird Island or Moku Manu The plants and rocky outcrops provide nesting areas for 18 species of seabirds, such as Red-footed Boobies and Brown Noddies, terns, shearwaters, and petrels

Blue gray noddy (Procelsterna cerulea) is a tern species that breeds on pinnacles; smallest tern in the world, specializes on halobates

Nihoa – Endemic Animals

Prior to 1980s, no trapdoor spiders documented in Hawai’i Upon their discovery, the genus was given the name Nihoa, because it was thought to exist nowhere else Eventually, over 23 species across the Pacific were found The species epithet, "mahina", means "moon" in Hawaiian, referring to how Sheila Conant discovered the spider by the light of the moon.

Nihoa – Endemic Animals

Thaumatogryllus conanti is a nocturnal species of cricket endemic to Nihoa, where it is found in Devil's Slide, a narrow ravine Named after Dr. Conant, who discovered it in the 1980s Only four known species in the genus Thaumatogryllus , all endemic to Hawai’i Another species is lives in lava tubes on the Island of Hawai’i

Nihoa – Introduced Animals

The introduced gray bird grasshopper (Schistocerca nitens) undergoes wild population swings on Nihoa, periodically denuding the island's vegetation They prefer drier climates, which may be why they have not thrived in the main Hawaiian Islands

Depth < 20m

Ikonos Imagery

Mokumanamana Island (Necker Island) is a dry volcanic island Age of 10.6 Million Years (MY) Geologists believe the island was once the size of O’ahu with a maximum paleo-elevation of 1,036 m Due to erosion its highest point, at Summit Hill, is now only 84.1 m above sea level

Depth < 20m

Ikonos Imagery

The largest atoll in the chain, shaped like a 28.9 km long crescent. Age of 12.3 MY

Tern island, the site of a FWS field station for long-term monitoring and the breeding site for 99% green sea turtles

Lagoon contains approximately nine low, sandy islets The sand islets are small, shift position, and disappear and reappear periodically

Lagoon contains one exposed volcanic pinnacle (La Perouse) 120-ft (37 m) high Last vestige of the high island from which the FFS atoll is derived

Depth < 20m

Ikonos Imagery

Gardner Pinnacles consists of two emergent basaltic volcanic peaks estimated to be 15.8 MY These represent the oldest high islands in the chain

Depth < 20m

Ikonos Imagery

Maro Reef is a submerged open atoll. Age is 19.7 MY At very low tide, a small coral rubble outcrop of a former island breaks above surface Discovered in 1820 by Captain Joseph Allen of the Maro, after whose ship reef was named Maro Reef supports no land biota (plants / animals)

Depth < 20m

Ikonos Imagery

Laysan is a formed atoll and the second largest island in the NWHI, after Midway Age is 20.7 MY It is well vegetated (except for its sand dunes) and contains a hyper-saline lake, which is one of only five natural lakes in the Hawaii

Depth < 20m

Ikonos Imagery

Lisianski Island (Papaapoho) is another raised atoll It is 23.4 MY Papaapoho is a Hawaiian term describing a flat area with a depression, which is exactly the shape of the island Its highest point is a 12.2 m high sand dune

Depth < 20m

Ikonos Imagery

A large atoll with several small islets. Atoll is 26.8 MY Unlike Lisianski and Laysan, Pearl and Hermes Atoll is a true atoll, fringed with shoals, permanent emergent islands, and ephemeral sandy islets The islets are periodically washed over when winter storms pass through the area

Depth < 20m

Ikonos Imagery

Midway Atoll is 28.7 MY and consists of three sandy islets: Sand, 4.56 km2 Eastern, 1.36 km2 Spit, 0.05 km2 Numerous patch reefs dot the sandy- bottomed lagoon In 1965, U.S. Geological Survey core samples hit solid basaltic rock 55 m beneath Sand Island and 378 m beneath northern reef

Depth < 20m

Ikonos Imagery

Kure Atoll is most northwestern island in the chain and occupies a singular position at the “Darwin Point”: the northern extent of coral reef development, beyond which coral growth cannot keep pace with geological subsidence This 29.8 million year old atoll is nearly circular, with a reef 9.6 km in diameter enclosing a lagoon with two islets that include over 0.81 km2 of emergent land

Seamounts and Banks

Unnamed Seamount – Pearl & Hermes

Countless banks and seamounts, characterized by large shallow (100 – 200 m deep) footprints

Major Threats to NWHI Atolls

Management of Kure Atoll – 5 minute Video

https://www.youtube.com/watch?v=KzXDKpjAuwI

Invasive Species

Kure

Simplified ecosystems

Susceptible to invasive species

Introduced weeds (like verbesina, below) monopolize space, nourish invasive ants and choke native plants and birds

Midway

Dynamic Features

FFS Pearl and Hermes

Highly dynamic islets and spits Change shape / size / location

Human Stabilization

Tern Island

Midway

Kure Variety of Structures: - Ports (Dredging) - Sea walls

- Runways

Sea Level Rise Impacts

Most of NWHI are low-lying and therefore potentially vulnerable to increases in global average sea level

Whale skate island, in French Frigate Shoals, disappeared in the late 1990s

Sea Level Rise – Study Rationale

Rising sea level could put up to 75 % of some low-lying Northwestern Hawaiian Islands underwater by 2100 Sea level rose 6 inches (0.15 m) in 20th Century Sea level rise projections by 2100 range from: median of 0.48 m to maximum of 0.88 m (Baker et al. 2006)

Sea Level Rise – Study Methods

Measurements of topography of French Frigate Shoals, Lisianski and Pearl and Hermes Reef in spring of 2005

Sandy atolls, composed of small islands, do not stand more than 6 1/2 feet above sea level

(Baker et al. 2006)

Sea Level Rise – Study Results

(Baker et al. 2006)

Sea Level Rise - Conclusions

(Baker et al. 2006)

Projected terrestrial habitat loss varied greatly among the islands examined: 3 to 65% under a median scenario (48 cm rise) 5 to 75% under the maximum scenario (88 cm rise) Spring tides would periodically inundate all land below 89 cm (median scenario) and 129 cm (maximum scenario) in elevation Sea level expected to continue increasing after 2100, which would have greater impact on atolls such as FFS and P&H Reef, where virtually all land is less than 2 m above sea level

Tsunami Inundation - March 12, 2011

Waves up to 4.5 feet high Waves washed over smallest island of atoll, called spit

Tsunami – March 12, 2011

Chicks and adult seabirds at Midway buried / washed out to sea

Sea Level Rise & Storminess

However, most NWHI seabird colonies on low-elevation islands and sea-level rise and accompanying high-water perturbations predicted to escalate with climate change. We identified 3 of 13 locally-breeding seabird species as highly vulnerable to sea level rise in the Hawaiian Islands:

(Reynolds et al. 2015)

Sea Level Rise & Storminess

(Reynolds et al. 2015)

Breeding phenology and synchrony of select (> 100

pairs) seabird species at

Midway Atoll compared with monthly mean of the top 5%

of wave heights and wind speeds.

Sea Level Rise & Storminess

(Reynolds et al. 2015)

Projected inundation of Laysan albatross nests at Midway Atoll for 4 sea-

level rise scenarios (+ 0.5, 1.0, 1.5, 2.0 m) using passive (a) and wave-driven

(b) models, including groundwater rise.

Sea Level Rise & Storminess

(Reynolds et al. 2015)

Projected inundation of Black-footed albatross

nests at Midway Atoll for 4 sea-level rise scenarios

(+ 0.5, 1.0, 1.5, 2.0 m) using passive (a) and wave-driven

(b) models, including groundwater rise.

Sea Level Rise & Storminess

(Reynolds et al. 2015)

Projected inundation of Bonin Petrel nests at

Midway Atoll 4 four sea-level rise scenarios

(+ 0.5, 1.0, 1.5, 2.0 m) using passive (a) and wave-driven

(b) models, including groundwater rise.

Sea level Rise - Management

Translocations – to High Islands

Sea level Rise - Management

Other technological fixes?

References MAPS: A Marine Biogeographic Assessment of the Northwestern Hawaiian Islands to Support the Papahanaumokuakea Marine National Monument http://ccma.nos.noaa.gov/ecosystems/sanctuaries/nwhi/ PHOTOS: http://www.shallenbergerphoto.com/pages/frameset1.htm