Climate Change

Sea Level Rise

Disappearing Island at French Frigate Shoals
Disappearing Island at French Frigate Shoals.

Over the course of the next century, global sea level is expected to rise due to thermal expansion of warming oceans and melting ice caps and glaciers. The remote low-lying islands of the Northwestern Hawaiian Islands (NWHI) may be particularly impacted as many of the islands rise no more than 2 meters (6.6 feet) above sea level. These islands and atolls support the primary subpopulations of Hawaiian monk seals and provide critical habitat for resting, molting and pupping necessary to survival.

The potential repercussions of reduced terrestrial habitat availability for NWHI monk seals are not fully understood. It is likely seals will move to suitable higher elevation areas, which would increase seal densities and may increase competition between seals resulting in negative population-level consequences.

Researchers continue to monitor for changes in sea surface heights and island acreage throughout the NWHI. This continued monitoring will assist in planning mitigation strategies necessary for long term protection of the NWHI and subsequently critical habitat for the Hawaiian monk seal.

Further Reading:

Baker JD, Littnan CL, Johnston DW
2006. Potential effects of sea level rise on the terrestrial habitats of endangered and endemic megafauna in the Northwestern Hawaiian Islands. Endangered Species Research 4(1): 1-10

Effects of El Niño

In temperate and polar regions where the vast majority of pinniped species are found, research has indicated seal and sea lion populations have crashed following El Niño events due to increased sea-surface temperatures and the resulting decline in prey availability. However, El Niño events are associated with cooler waters in Hawaii, and studies have demonstrated improved body condition and survival of Hawaiian monk seal pups and juveniles following El Niño years. These cooler waters can lead to improved diet or foraging efficiency of Hawaiian monk seals through changes in prey availability, distribution, or quality. Impacts of oceanographic variability on monk seal foraging continue to be evaluated.

Further Reading:

Antonelis GA, Baker JD, Polovina JJ
2003. Improved body condition of weaned Hawaiian monk seal pups associated with El Niño events: potential benefits to an endangered species. Marine Mammal Science 19(3): 590-598.
Baker JD, Howell EA, Polovina JJ
2012. Relative influence of climate variability and direct anthropogenic impact on a sub-tropical Pacific top predator, the Hawaiian monk seal. Marine Ecology Progress Series 469: 175-189. DOI: 10.3354/meps09987
Baker JD, Johanos TC, Wurth TA, Littnan CL
2013. Body growth in Hawaiian monk seals. Marine Mammal Science. DOI: 10.1111/mms.12035
Baker JD, Polovina JJ, Howell EA
2007. Effect of variable oceanic productivity on the survival of an upper trophic predator, the Hawaiian monk seal Monachus schauinslandi. Marine Ecology Progress Series 346: 277-283.
Parrish FA, Howell EA, Antonelis GA, Iverson SJ, Littnan CL, Parrish JD, and Polovina JJ
2011. Estimating the Carrying Capacity of French Frigate Shoals for the Endangered Hawaiian Monk Seal Using Ecopath with Ecosim. Marine Mammal Science. DOI: 10.1111/j.1748-7692.2011.00502.x