Building "green infrastructure" into protection of vulnerable island communities

The Issue

The Issue

The Florida Keys are 852 islands stretching 200 miles from Miami to the Dry Tortugas.  They are connected to the mainland by one road - U.S. Highway 1 - an electrical transmission line and a drinking water aqueduct, all of which terminate in Key West, the county seat of Monroe County. The Keys were home to about 73,000 people and a tourism destination for more than 3.8 million visitors in 2010. They also provide vital habitat for wildlife and plants including more than 30 species that are listed by the federal or state government as threatened or endangered species. Many of these are found nowhere else on Earth. 

The famous coral reefs offshore underpin a $2.3 billion annual ocean economy centered on fishing and diving off the Keys, but this unique resource is highly sensitive to rising ocean temperatures and storms.  And with more than ninety percent of the Keys’ land area less than 5 feet above sea level and within a mile of the shore, the islands are extremely vulnerable to hurricane-driven storm surges and sea level rise.  The 2007 property value of the land at risk of inundation from 5 feet of sea level rise was about $25 billion; well more than half of the total land value of the Keys.

According to the National Oceanic and Atmospheric Administration’s tide gauge at Key West harbor, sea level has risen about nine inches over the last century, on par with the global average.  This may seem insignificant, but low-lying roads, private property and natural areas are already flooding during the highest tides of the year.  In natural areas this regular saltwater flooding influences which plants can survive and the availability of freshwater; two factors critical for wildlife.  In island communities it affects insurance costs, property values and peace of mind.  Storm surges, although short-lived compared to chronic sea level rise, also strongly influence ecological, social and economic dynamics.

Documented acceleration of sea level rise over the last century and scientific predictions of an increasing rate of rise in the century to come have led to numerous predictions for the future of the Florida Keys.  Most recently the Southeast Florida Climate Change Compact, a collaborative effort among Monroe, Miami-Dade, Broward and Palm Beach County governments, conservatively estimated 3-7 inches of sea level rise by 2030 and 9-24 inches by 2060.  Increased hurricane intensity is also predicted for the century ahead.