Storm surge on top of sea level rise exacerbates coastal flooding during hurricanes.

Courtesy of NOAA

Because environmental, cultural, and socioeconomic systems are tightly coupled, climate change impacts can either be amplified or reduced by cultural and socioeconomic decisions. In many arenas, it is clear that societal decisions have substantial influence on the vulnerability of valued resources to climate change. For example, rapid population growth and development in coastal areas tends to amplify climate change related impacts. Recognition of these couplings, together with recognition of multiple sources of vulnerability, helps identify what information decision-makers need as they manage risks.

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Impacts are particularly severe when critical systems simultaneously fail. We have already seen multiple system failures during an extreme weather event in the United States, as when Hurricane Katrina struck New Orleans.² Infrastructure and evacuation failures and collapse of critical response services during a storm is one example of multiple system failures. Another example is a loss of electrical power during heat waves or wildfires, which can reduce food and water safety.³ Air conditioning has helped reduce illness and death due to extreme heat,⁴ but if power is lost, everyone is vulnerable. By their nature, such events can exceed our capacity to respond.⁵ In succession, these events severely deplete resources needed to respond, from the individual to the national scale, but disproportionately affect the most vulnerable populations.⁶

In many social and natural systems, climate change combines with other stresses to cause or expand impacts. For example, coral reefs are threatened by a combination of ocean acidification caused by increased carbon dioxide, rising ocean temperatures, and a variety of other factors caused by human activities.

Coral Bleaching

Warming Seas Are a Double-blow to Corals

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Warm water caused this coral colony to “bleach” as it expelled the symbiotic algae that gave it color and nourishment. The coral then experienced more disease, which eventually killed the colony.

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Recent research indicates that 75% of the world’s coral reefs are threatened due to the interactive effects of climate change and local sources of stress, such as overfishing, nutrient pollution, and disease.^7,8,9,10,11 In Florida, all reefs are rated as threatened; with significant impacts on valuable ecosystem services they provide.¹² Caribbean coral cover has decreased 80% in less than three decades.¹³ These declines have in turn led to a flattening of the three dimensional structure of coral reefs and hence a decrease in the capacity of coral reefs to provide shelter and additional resources for other reef-dependent ocean life.¹⁴

The relationship between coral and zooxanthellae (algae vital for reef-building corals) is disrupted by higher than usual temperatures and results in a condition where the coral is still alive, but devoid of all its color (bleaching). Bleached corals can later die or become infected with disease.^15,16 Thus, high temperature events alone can kill large stretches of coral reef, although cold water and poor water quality can also cause localized bleaching and death. Evidence suggests that relatively pristine reefs, with fewer human impacts and with intact fish and associated invertebrate communities, are more resilient to coral bleaching and disease.¹⁷

Agriculture, water, energy, transportation, and more, are all affected by climate change. These sectors of our economy do not exist in isolation and are linked in increasingly complex ways. For example, water supply and energy use are completely intertwined, since water is used to generate energy, and energy is required to pump, treat, and deliver water – which means that irrigation-dependent farmers and urban dwellers are linked as well.

Heat and drought lead to cascading impacts among sectors including agriculture, water, and energy.

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A recent illustration of these interconnections took place during the widespread drought of 2011-2012 when high temperatures caused increased demand for electricity for air conditioning, which resulted in increased water withdrawal and consumption for electricity generation. Heat, increased evaporation, drier soils, and lack of rain led to higher irrigation demands, which added stress on water resources required for energy production. At the same time, low-flowing and warmer rivers threatened to suspend power plant production in several locations, reducing the options for dealing with the concurrent increase in electricity demand.

With electricity demands at all-time highs, water shortages threatened more than 3,000 megawatts of generating capacity – enough power to supply more than one million homes.¹⁸ As a result of the record demand and reduced supply, electricity prices spiked.¹⁹