The "bleaching" or some kind of harm to the world's coral reefs has been blamed on man-caused global warming or climate change. Coral reefs have existed in the world's oceans for millions of years, through countless climate and environmental changes. These ancient coral reefs are preserved in the geologic record as limestone rocks and geologists study them intensely. I am highly skeptical that any changes observed in today's coral reefs are caused by global warming. I am not alone in this line of thought. Consider the following report.
Are U.S. Coral Reefs Endangered by Global Warming?
Written by The Center for Science & Public Policy
Wednesday, 26 September 2007
Are U.S. Coral Reefs Endangered by Global Warming?______________________________________________________________________Executive Summary
• In May 2006, the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service (NMFS) listed two species of corals, elkhorn coral (Acropora palmata) and staghorn coral (Acropora cervicornis ), as “threatened” under the Endangered Species Act.• In September 2007, the Center for Biological Diversity (the environmentalist organization that first petitioned the NMFS to list the corals under the Endangered Species Act) won a settlement in a lawsuit it brought against NMFS to end its delay in designating a “critical habitat” for the elkhorn and staghorn coral.
• The Center for Biological Diversity contends that these corals are “the first, and to date only, species listed under the Endangered Species Act due to threats from global warming.” Kieran Suckling, the policy director of the Center, “We think this victory on coral critical habitat actually moves the entire Endangered Species Act onto a firm legal foundation for challenging global-warming pollution.”
• A close look at the scientific evidence, however, reveals that the impact of global warming on the overall health of coral species is likely to be positive—towards increased species diversity and richness and habitat expansion—and there is evidence that these changes are already underway.
• For example, thickets of staghorn coral were discovered in Broward County, Florida in 1998 where none had been observed in previous decades. Colonies of elkhorn coral have been observed as far north as Pompano Beach in northern Broward County as well as seen for the first time in 2002 on reefs of the Flower Garden Banks in the northern Gulf of Mexico.
• By listing the elkhorn and staghorn coral species as “threatened” under the Endangered Species Act, the NMFS recognized the widespread decline in the abundance of these corals throughout their range in the Caribbean—a decline that is likely related to the interplay of a large number of factors.
• However, the hope that this designation will somehow become a tool for global warming legislation is grossly misplaced. Global warming will likely be a benefit to elkhorn and staghorn corals, especially along the Florida coast where increasing ocean temperatures should encourage coral reef development further and further northward.• Instead of aiming their goal on trying to alter global climate trends in the name of preserving coral species, organizations such as the Center for Biological Diversity should focus more on local management and recovery issues that could enhance the health of elkhorn and staghorn corals in the U.S. waters is the western tropical Atlantic Ocean.
______________________________________________________________________Are U.S. Coral Reefs Endangered by Global Warming?In May 2006, the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Fisheries Service (NMFS) listed two species of corals, elkhorn coral (Acropora palmata) and staghorn coral (Acropora cervicornis), as “threatened” under the Endangered Species Act. These corals species have been among the primary reef builders in Florida, Puerto Rico, and the U.S. Virgin Islands. The NMFS found that significant declines in the populations of these acroporid coral species, upwards of 80 to 90 percent had occurred across their range during the past 20 to30 years, as a result of a complex interplay of factors, that include diseases (effecting corals directly as well as other reef species that aid in the survival of corals), overfishing, water quality, hurricanes, anchoring and ship grounding, and elevated temperatures.
In September 2007, the Center for Biological Diversity (the environmentalist organization that first petitioned the NMFS to list the corals under the Endangered Species Act) won a settlement in an lawsuit it brought against NMFS to end its delay in designating a “critical habitat” for the elkhorn and staghorn corals—something that the NMFS was required to do under the Endangered Species Act, but had thus far not completed.The idea behind this “critical habitat” requirement is that habitat loss is seen by some to be a primary cause of species endangerment in the United States.
According to the Center for Biological Diversity, species which have a "critical habitat" designated under the Endangered Species Act have about a doubled chance of recovery compared to those that without a protected habitat [note: The U.S. Fish and Wildlife Service, under both the Clinton and Bush Administrations, has argued to the contrary. For example, Jamie Clark, Clinton’s Fish and Wildlife director, testified before Congress in 1999 that the “designation of official critical habitat provides little additional protection to most listed species, while it consumes significant amounts of scarce conservation resources”].
According to the NMFS:
The Endangered Species Act (ESA) requires the federal government to designate “critical habitat” for any species it lists under the ESA. “Critical habitat” is defined as: (1) specific areas within the geographical area occupied by the species at the time of listing, if they contain physical or biological features essential to conservation, and those features may require special management considerations or protection; and (2) specific areas outside the geographical area occupied by the species if the agency determines that the area itself is essential for conservation.
Critical habitat designations must be based on the best scientific information available, in an open public process, within specific timeframes. Before designating critical habitat, careful consideration must be given to the economic impacts, impacts on national security, and other relevant impacts of specifying any particular area as critical habitat. The Secretary of Commerce may exclude an area from critical habitat if the benefits of exclusion outweigh the benefits of designation, unless excluding the area will result in the extinction of the species concerned.
The ESA protects threatened and endangered species in several ways. Under Section 7, all federal agencies must ensure that any actions they authorize, fund, or carry out are not likely to jeopardize the continued existence of a listed species, or destroy or adversely modify its designated critical habitat. These complementary requirements apply only to federal agency actions, and the latter only to habitat that has been designated. A critical habitat designation does not set up a preserve or refuge, and applies only when federal funding, permits, or projects are involved. Critical habitat requirements do not apply to citizens engaged in activities on private land that do not involve a federal agency.
The settlement will require the NMFS to pursue designating a critical habitat for the elkhorn and staghorn corals and is hailed as a triumph by the Center for Biological Diversity as they contend that these corals are “the first, and to date only, species listed under the Endangered Species Act due to threats from global warming.” Apparently, they think that they can use the Endangered Species Act as a new tool in their fight against global warming. According to Kieran Suckling, the policy director of the Center, “We think this victory on coral critical habitat actually moves the entire Endangered Species Act onto a firm legal foundation for challenging global-warming pollution.”
However, a closer look at the scientific evidence reveals that the impact of global warming on the overall health of coral species is likely to be positive—towards increased species diversity and richness and habitat expansion—and there is evidence that these changes are already underway.
Prominent coral researchers William Precht and Richard Aronson have recently published papers (e.g. Precht and Aronson, 2004) and given presentations (e.g. Precht and Aronson, 2006), indicating that the current range inhabited by elkhorn and staghorn corals is not as expansive as it was 10,000 to 6,000 years ago—a time when the Caribbean were warmer than present. Cold temperatures limit the range of corals, not warm ones. Coral reefs are generally limited to regions with minimum ocean temperatures greater than about 18ºC (68ºF) and there is little evidence that maximum ocean temperature limits the latitudinal distribution of coral reefs.
While high-temperature induced bleaching events, such as the ones associated with the 1998 El Niño, can lead to coral reef damage and in some cases death, despite how dramatic they may appear, have not been tied to any reef extinctions. In fact, coral reefs flourish in the places which have the highest ocean temperatures in the world.Precht and Aronson describe the range variability of corals along Florida’s southeast coast since the end of the last ice age:
Relict, submerged, early to middle Holocene [about 10,000 to 6,000 years ago] reefs are found throughout southeast Florida. Warmer conditions during this period apparently permitted a more northerly distribution of acroporid-dominated reefs. As temperatures cooled after the middle Holocene [from 6,000 years ago to present], the northern limit of the Florida reef tract moved south to its current position.
In the early to middle Holocene, Acropora-dominated reefs up to 10 m thick were well developed as far north as Palm Beach County, indicating that conditions along the platform margin were more conducive than today to the growth of acroporid corals and the deposition of acroporid-dominated reef framework.The figure below show the present-day range of acroporid corals in southeastern Florida along with the location of relict reefs from the 10,000 to 6,000 years ago that extended much further northward long the coast. Precht and Aronson describe a similar situation in Western Australia.
They summarize that “These paleoecological examples of species replacements and range expansions, especially those concerning acroporids, emphasize the varied responses of coral species and their ability to reconstitute reef communities in the face of rapid environmental change not related to human modification of the seascape.”
In other words, as the temperatures of the world’s oceans change over time, the world’s coral species, including acropora species such as elkhorn and staghorn corals, expand and contract their ranges as conditions dictate. Figure 1: Map of Florida showing the present-day distribution of the reef tract and the northern limit of acroporid corals (green), the relict Holocene reef tract dominated by acroporid corals (orange), and the location of recently discovered thickets of acroporid corals (star). (From Precht and Aronson, 2004).
Precht and Aronson provide evidence that range expansion is currently ongoing, as elkhorn and staghorn corals move into locations that were likely previously too cold for their long-term survival.
Precht and Aronson write:
There is mounting evidence that coral species are responding to recent patterns of increased SSTs [sea-surface temperatures] by expanding their latitudinal ranges…In Florida, numerous thickets of staghorn coral, some up to 700 m2 in area, are now established north of their previously known range. Detailed studies documenting the composition, structure, and reproductive viability of these populations have been conducted in seven of these thickets. Elkhorn coral has also been observed colonizing shallow reef areas north of extant populations. The two Acropora species have expanded more than 50 km northward in just the last few decades.They go on to cite specific examples. Along the southeast coast of Florida, “[S]patially extensive thickets of staghorn coral, Acropora cervicornis, were discovered in Broward County, Florida in 1998 where they had not been observed during the 1970s and 1980s [see Figure 1].
More recently, colonies of elkhorn coral, Acropora palmate, have been observed as far north as Pompano Beach in northern Broward County. Also, elkhorn coral was seen for the first time in 2002 on reefs of the Flower Garden Banks in the northern Gulf of Mexico.” Precht and Aronson suggest that this northward range extension is a result in increasing ocean temperatures. “The sudden appearance of Caribbean acroporid corals well north of their previously know range extent is associated with decadal-scale increases in annual sea-surface temperature in the western Atlantic.” Clearly, the rapid response of these coral species to take advantage of the opening of viable habitat shows that they have the ability to respond to changing conditions.
Further, Precht and Aronson provide paleoevidence that suggests that the northward establishment of coral colonies represents a true range expansion rather than simply a range shift (with a corresponding shrinkage of the southern end of the range). In fact, these researchers find that not only should rising ocean temperatures expand the corals’ range, but also expand the species richness and diversity:
It has been argued that tropical coral assemblages exhibit stability and persistence through Quaternary time [past 1.8 million years, the geologic period dominated by the recent cycles of ice ages] and therefore constitute the most important database for studying abrupt change in modern reefs. A key aspect of this argument is that warmer temperatures during the last major interglacial period were not associated with contraction of the southern range of the acroporids or the demise of reef systems in the tropics. Based on these results, and because SSTs in global climate models generally do not exceed 32°C in the Caribbean, it is unlikely that future global warming will lead to the catastrophic collapse of reef systems, the extirpation of acroporid corals, or the contraction of their southern range in the tropical Caribbean, as some have predicted.
Reefs in Florida, the Gulf of Mexico, and Bermuda, are more likely to show changes in species richness and diversity with climatic warming.At the latitudinal extremes of Caribbean reef systems, an increase in SST of only 1–2°C should encourage temperature-sensitive corals such as the acroporids to expand their ranges. Reyes Bonilla and Cruz Piñón (2002) made a similar prediction for warming seas along the Pacific coast of Mexico, suggesting that coral species richness will increase the most at subtropical latitudes.
Along the eastern Pacific, as many as eight coral species have recently been identified north of their previously known ranges, while at Lord Howe Island in Australia the arrival of six species has been observed within the past decade (emphasis added).While clearly warming oceans seem to invite an expansion of coral reefs, Precht and Aronson do caution that 1) there is a complex interplay between rising ocean temperatures and other factors that impact coral health, and 2) factors besides ocean temperatures influence reef development.
Thus, it is not entirely possible to know the true course of the future of elkhorn, staghorn, and other coral species in the Caribbean and U.S. waters. But the one thing that history does show is that coral species have survived climate swings in the past, and typically expand their range and diversity during warm periods and contract during colder periods.
Thus, a future global warming does not, in and of itself, portend a bleak future for Caribbean coral (or coral worldwide).By listing the elkhorn and staghorn coral species as “threatened” under the Endangered Species Act, the NMFS recognized the widespread decline in the abundance of these corals throughout their range in the Caribbean—a decline that is likely related to the interplay of a large number of factors. It also recognizes the need to stem this decline and aid in the recovery process.Designating “critical habitats” may be an important part of the process.
However, the hope that this designation will somehow become a tool for global warming legislation is grossly misplaced. Global warming will likely be a benefit to elkhorn and staghorn corals, especially along the Florida coast where increasing ocean temperatures should encourage coral reef development further and further northward. Since, currently, the southern portions of Florida define climatologically the northernmost portion of the coral habitat in the western Atlantic, a warming climate presents the opportunity for a habitat expansion that could bring corals further northward and closer to the U.S. mainland.
Since coral reefs represent a major tourist destination, not only would a northward range expansion be a benefit to the corals themselves, but may well also represent enhanced economic opportunities along the southeastern U.S. coast. Figure 2: Range (in yellow) of acroporid corals in the Caribbean (from Precht and Aronson, 2004).
Thus, instead of aiming their goal on trying to alter global climate trends in the name of preserving coral species, organizations such as the Center for Biological Diversity should focus more on local management and recovery issues that could enhance the health of elkhorn and staghorn corals in the U.S. waters is the western tropical Atlantic Ocean.
Such local habitat issues are a better fit of the Endangered Species Act than are global issues involving worldwide carbon dioxide emissions. Local greenhouse gas emissions controls will have no impact on the rate of future climate change. And even more importantly, scientific evidence of past and present coral behavior patterns indicates that high ocean temperatures enable and encourage a wider distribution of corals and coral reef ecosystems.
References:Precht, W.F., and R.B. Aronson, 2004. Climate flickers and range shifts of reef corals. Frontiers in Ecology and the Environment, 2, 307-314: http://faculty.disl.org/Publications/Precht%20and%20Aronson%20Frontiers%202004.pdf
Precht, W.F., and R.B. Aronson, 2006. Rapid Range Expansion of Reef Corals in Reponse to Climatic Warming. Annual Meeting of The Geological Society of America. Oct. 22-25: http://gsa.confex.com/gsa/2006AM/finalprogram/abstract_105499.htm
Reyes Bonilla H and Cruz Piñón G. 2002. Influence of temperature and nutrients on species richness of deep-water corals from the western coast of the Americas. Hydrobiologia 471: 35–41.