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Climate Change
Impacts of Climate Change on Habitat and Species in Florida
Elkhorn coral, Acropora palmata, (pictured) along with staghorn coral, Acropora cervicornis, important reef building corals, were the first species listed threatened under the Endangered Species Act due to climate change impacts.
© Larry Benvenutti
Coral Reefs
Florida's reefs, which constitute the world’s third largest coral barrier reef system, are beautiful and of enormous economic and ecological value to the region. Not only do Florida’s reefs generate more than 40,000 jobs, $1.1 billion in income and $2.3 billion in sales annually in Monroe, Miami-Dade and Broward counties, but they also protect our coasts and beaches from erosion, flooding and property damage. By buffering vital seagrass and mangrove habitat from wave action, reefs help reduce the impact of hurricanes and storm surges.
Protected portions of the Key’s reef, where commercial and recreational fishing is prohibited, also serve as important nursery grounds for commercially valuable fish. After species such as grouper, snapper and spiny lobster spawn here, ocean currents distribute their offspring north along the eastern seaboard. This process supports vital commercially fisheries (Monroe County fishermen land nearly 20 million pounds of seafood annually), and contributes to the long-term health and viability of the marine ecosystem.
Although overfishing and water pollution have historically been the most significant threats to the health of Florida’s reefs, climate change is now exacerbating and compounding these local stresses. The most harmful effect of climate change on reefs is coral bleaching, a process during which corals lose the colored, symbiotic algae from their tissues. This phenomenon, which is attributed to elevated water temperatures, exposes coral’s fragile white skeletons, and can produce a range of effects, including reduced growth rates, lower reproductive ability, increased susceptibility to disease and even death of the coral colony. Once an unusual occurrence in Florida and the Caribbean, bleaching is now regularly monitored. Following a general trend in warmer summer water temperatures, bleaching has occurred to some degree every year in Florida since 2005. Bleaching related coral mortality reached 50% for locations in the Caribbean outside Florida during 2005. Scientists predict that mass coral bleaching may become an annual event globally if the world’s carbon dioxide emissions continue on a “business as usual” trajectory. If that happens, there will be little time for coral to recover between bleaching events, and populations will decline rapidly.
Another threat that climate change poses for coral reefs is ocean acidification. Since 1980, approximately 30 percent of the carbon dioxide that has been released into the atmosphere from the burning of fossil fuels has been absorbed by the ocean. Absorbing carbon dioxide has not only made sea water more acidic than it was prior to industrialization, but it has also reduced the concentrations of some minerals in sea water (primarily calcium carbonate) that are essential skeletal building blocks to marine organisms like coral, mollusks, sea stars, brittle stars, sea urchins, and many others. As concentrations of these minerals in sea water continue to decline, scientists worry that coral and other marine organisms may have trouble growing, and that their shells and skeletons may actually dissolve.
Climate change is increasing the susceptibility of coral to disease”
© Jeff Foott
Climate change is also increasing the susceptibility of Florida’s coral to disease outbreaks —coral diseases are now four times more likely than they were before 1994 —and these diseases can have devastating effects. Coral in the U.S. Virgin Islands suffered an average decline of 51% due to bleaching and subsequent disease in 2005.
When these climate-change induced threats are overlaid, it becomes clear why scientists are concerned about how reefs will cope with climate change, both locally and at global scales. Not only are Florida’s reefs challenged by local forces (poor water quality, boat groundings, fishing pressures), but they also have to contend with additional pressures from climate change: increased risk of bleaching, enhanced susceptibility to disease, and reduced growth rates from ocean acidification. Reef health may decline rapidly as the earth warms and efforts to enhance the resilience of reefs may become essential to their long-term survival in tandem with reducing U.S. and global carbon dioxide emissions.
The Florida Everglades
Scientists worry that he Florida Everglades, in the midst of the world’s largest and most expensive restoration effort, will be affected by climate change, especially if restoration projects are not completed in a timely matter. According to the Tufts University study, sea levels will likely encroach 12-24 miles inland by 2060, which will completely inundate the lower Everglades and compromise its ability to support many species that have historically thrived there: wood storks, American crocodiles, Florida panthers, and myriad other species attuned to the region’s fluctuations of freshwater levels spread across wet and dry seasons. Up to one-third of the Everglade’s species richness may be lost. Of critical importance to the future of the Everglades will be the ability of scientist and managers to predict climate change impacts and to adapt restoration strategies to enhance the long-term sustainability of this unique ecosystem.
The Florida Keys National Marine Sanctuary
According to the 2007 Government Accountability Office report, climate change is expected to directly impact the 2,800 nautical mile (approximately 9.500 square kilometer) Florida Keys National Marine Sanctuary, which protects the marine ecosystem that surrounds the Florida Keys, including spectacular seagrass meadows, mangrove islands, and the world’s third largest coral reef. The report states that the land and water resources from the Florida Keys are already being impacted by climate change. However, resource managers are struggling to determine how to address these changes, and have not yet addressed climate change effects in their management and planning efforts. Impacts such as rising ocean temperatures are causing the Sanctuary’s coral reefs to bleach, and raised ocean levels have contributed to habitat loss and shifts in species distribution. These climate change impacts are also expected to have an economic and social effect, impacting tourism, diving, and fishing within and outside Sanctuary boundaries.
WWF has been active in Sanctuary affairs since its creation. We have played a leadership role in securing local, state, and federal approval for the Sanctuary in 1990, which is the third largest unit in the national marine sanctuary program. We helped Sanctuary staff develop, implement, and review its Management Plan, and helped secure federal, state, and local approval for the Tortugas Ecological Reserve between 2000 and late 2006, the largest fully-protected marine reserve in the Western Hemisphere.
© South Florida Water Management District
Mangrove Forests
Accelerated sea level rise also threatens Florida’s valuable mangrove forests, which protect Florida’s shoreline from erosion and storm surges, filter pollution, are home to many unique species of animals and plants, and serve as nursery and feeding grounds for myriad fish, marine mammals and invertebrates. Mangroves have historically been able to migrate landward or seaward in response to changing sea levels, but the extent of coastal development in Florida, coupled with the increasing pace of sea level rise brought on by climate change, may severely limit this ability. In Florida, researchers have already documented the suffocation of black mangroves due to excessive storm surge flooding. The increasingly intense storms expected to accompany climate change will also endanger the long-term health of Florida’s mangrove forests. (Several studies have shown that large storms have produced mass mortality in Caribbean mangrove forests over the past 50 years.) The Tufts University study projects that Florida will lose 99 percent of its mangroves by 2060, when sea level rise will likely convert them to shallow marine habitat or open water.
Marshlands
Climate change-induced sea level rise is expected to take a disproportionate toll on coastal wetlands, which are the exclusive home of several bird species, including clapper rails, long-billed marsh wrens, and the highly endangered Cape Sable Seaside sparrow. Like mangrove forests, wetlands are also nursery grounds for many commercially and recreationally important fish and shellfish, plus they help filter pollution and to mitigate storm impacts on developed areas.
Between 1985 and 1995, the southeastern United States lost an estimated 32,000 acres of coastal marshland, and additional losses in the region are likely as climate change accelerates rates of sea level rise. Even marshlands that are not completely submerged by rising seas will nonetheless be affected. Officials at Everglades National Park have begun to notice vegetative changes in the outer rim of the ecosystem, the result of saltwater intrusion into areas where waters used to be predominantly fresh. Although it may be possible to shore up developed areas against sea level rise there are few practical options for protecting natural ecosystems as a whole. Wetlands may take a disproportionate hit as this phenomenon unfolds.
Sea Grass Beds
Florida’s extensive, highly productive seagrass meadows will also be affected. Not only may warmer ocean temperatures fuel ecological community changes from eutrophication—decreased primary productivity, reduced oxygen levels, excessive plant growth and decay, and reduced water quality that can adversely affect fish and marine life—but they may alter growth and distribution patterns for seagrass species. Seagrass distribution and abundance are governed by salinity, light, depth and currents, which are all sensitive to climate change. Climate change may also intensify the frequency and severity of tropical storms, which damage seagrass beds and endanger their long-term recovery and health.
Tidal Flats
Tidal flats are important habitat for popular game fish, such as bonefish, yellowtail snapper, and tarpon. Unfortunately, a recent report by the National Parks Conservation Association suggests that Biscayne Bay may lose 79 percent of its tidal flats by 2100 because of sea level rise, and that Florida Bay could lose 98 percent of its flats by 2050 . These habitat loses may have adverse impacts on the availability and health of fish and invertebrate stocks that rely on this habitat.
Coastal hardwood forests
EPA’s Global Change Research Program reports that saltwater intrusion and sea level rise are heavily impacting coastal forests in the southeast United States, including Florida. Parts of south Florida and Louisiana are now home to “ghost forests” where altered high tide levels have produced soils too salty for bald cypress, live oak, and sabal palm species. Florida’s Forestry Division reports “massive die-offs” of sabal palm along a 40 mile stretch of coastline between Cedar Key and Homosassa Springs since 1991, and significant live oak and bald cypress mortality around Florida as far as 30 miles inland, both likely due to rising sea levels. Temperature changes induced by climate change may also alter the species composition of Florida’s forests, which currently cover almost half the state’s total land area (approximately 29,000 square miles). Loblolly-shortleaf and longleaf-sash pines may become less abundant as temperatures rise beyond the tolerance of those species, while oak-hickories and oak-pines may become more common. Forests which are not able to migrate north (to escape rising temperatures, lower precipitation, and more common pests and diseases) may simply sicken and die.
Climate change may skew the sex ratios of sea turtles hatchlings, since sex determination in turtles is temperature dependent
© Anja G. Burns
Wildlife and Species
Climate change may pose a variety of threat to endangered sea turtles, including erosion of nesting beaches from sea level rise and increased storm activity loss of feeding habitats (coral reefs and seagrass beds), and loss of access to offshore feeding habitat due to changes in currents. Increasing beach temperatures can also skew sea turtle sex ratios. Because sex determination in turtles is temperature dependent, higher temperatures lead to more female turtles with only 1.5 ºC separating the sexes. Scientists predict that a 2ºC increase in temperature could dramatically skew the sex ratio, and a 4ºC increase would virtually eliminate male offspring.
Other species that may be adversely affected by climate change include the American Crocodile and West Indian Manatee (both of whose habitat may be damaged by saltwater intrusion), wading birds (abundance of whose prey (fish) may be affected by salinity changes linked to global warming), and marine species like shrimp, blue crab, and spiny lobster (also affected by salinity). The critically endangered Cape Sable Seaside sparrow has also already been affected by climate change. According to a recent report by the National Parks Conservation Association, the CSSP no longer lives on Cape Sable. “It has been forced north, in part by rising seas.”
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