09: Coastal Issues

With rising sea level, risks to vital public infrastructure will increase and will be exposed to future damage from erosion and flooding.

Climate-related changes to the ocean—warming waters and oxygen depletion—can reduce available habitat for economically important marine species.

The severity of coastal erosion, flooding, inundation, and other hazards will increase due to sea-level rise and continued coastal development.

Coastal development creates impediments to the natural migration of coastal wetlands, resulting in the loss of wetlands and their benefits.

Figure 9.2: Sea-level rise and El Niño events. The implications of sea-level rise for coastal California cannot be understood in isolation from other, shorter-term sea-level variability related to El Niño events, storms, or extreme tides that affect the coast. As historical experience has shown, the greatest damage to coastal areas has occurred during large El Niño events (for example in 1940–41, 1982–83, and 1997–98) when short-term sea-level increases occurred simultaneously with high tides and large waves. If sea level were still at the same elevation in 2005 as it was in 1900, a major El Niño event like that in 1997–98 would fall within the “noise” of today’s interannual variability. As sea level is continuing to rise, the impacts of future large ENSO events will be greater than those historic events of similar magnitude, exposing coastal areas to the combined effects of sea-level rise, elevated sea levels from El Niño events, and large waves. Source: Pacific Decadal Oscillation monthly values index.

Figure 9.3: Monthly value for the Pacific Decadal Oscillation. The period from about 1945 to 1978 was a cool PDO period marked by an overall calm or benign coastal climate, but also was a period of intensive growth and development along the California coast. The vertical axis is a dimensionless PDO index based on North Pacific sea-surface temperature variability. 9.3(a) adapted from Pacific Decadal Oscillation monthly values index, http://jisao.washington.edu/pdo/; data in 9.3(b) and (c) from http://silvis.forest.wisc.edu/old/Library/HousingDataDownload. php?state=California&abrev=CA; see also Hammer et al. (2004).

Figure 9.4: Estuary wetland migration area by land-cover type in the Monterey Bay region. Different land-use types will have different capacities to accommodate wetland migration, ranging from urban areas (which are unlikely to accommodate migration at all) to public natural areas (which will likely accommodate migration completely). Between these extremes are agricultural areas and privately owned natural areas, both of which could accommodate migration if landowners choose not to prevent it, such as by not fortifying or armoring their lands. Adapted from Gleason et al. (2011, 23); Heberger et al. (2009).

Figure 9.5: Impacts of climate change on marine species distributions and habitat. Many marine species are confined to particular habitats based on water temperature, salinity, or depth. In panel (a) Humboldt squid are confined at their northern edge by temperature. In 2003, the northern edge reached the mouth of the San Francisco Bay, but has recently expanded as far north as Alaska. In panel (b) some fish have limited habitat due to temperature levels of shallower waters above and oxygen or acidity levels of deeper waters below. As surface waters warm and oxygen minimum zones expand or acidity increases, the available habitat for these species is compressed. This leads to lower available resources and potentially increased predation. Source: Bograd et al. (2010), Stramma et al. (2011).

Figure 9.6: Coastal impacts of ocean acidification. This image depicts the aragonite saturation depth on the continental shelf of western North America; warmer colors indicate shallower depths. Aragonite is one of the two most common forms of calcium carbonate, which forms naturally in almost all mollusk shells. Below this depth, it becomes difficult for mollusks and other species to precipitate the calcium carbonate necessary to make shell material. Corrosive waters––those that begin to dissolve calcium carbonate––now occur at shallower depths than in the past because the ocean is absorbing increasing amounts of CO2 from the atmosphere. Note that in transect 5, corrosive water reaches the ocean surface north of Eureka and Arcata, California. Modified from Feely et al. (2008), reprinted with permission from the American Association for the Advancement of Science.

Figure 9.7: Impacts to San Francisco and Oakland International Airports. The impacts to San Francisco and Oakland airports will require planning and resources to ensure that these major economic drivers for the San Francisco Bay Area can continue to operate in the future. Modified from Siegel and Bachand (2002), Knowles (2008); see also http://www.bcdc.ca.gov/planning/climate_change/index_ map.shtml, Central Bay West Shore map 16 & 55, Central Bay East Shore map 16 & 55.

Figure 9.8: Coastal armoring in Southern California. One-third of the shoreline of Southern California (including Ventura, Los Angeles, Orange and San Diego Counties) has now been armored. The photo shows the shoreline in 2010 in Encinitas, in northern San Diego County. Photo courtesy of Kenneth and Gabrielle Adelman of the California Coastal Records Project (http://www.californiacoastline.org/).

Figure 9.9: California coastal managers’ attitudes toward climate change. Well over 80% of California coastal managers are concerned with climate change. The proportion saying they are “very concerned” increased significantly over the past six years. Meanwhile, local managers feel only moderately well informed, indicating a significant need for education. One indication of their readiness to advance adaptation planning is the high proportion of respondents (75%) who report that they already consider the implications of climate change in their personal and professional lives. Source: Moser (2007), Moser and Tribbia (2007), Hart et al. (2012).