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General (Climate)

1 . Global (2004)
GLOBAL CLIMATE CHANGE


The major emerging threat to coral reefs in the last decade has been coral bleaching and mortality associated with global climate change (GCC), especially major El Niño/ La Niña events. The 1998 global coral bleaching event effectively destroyed 16% of the world’s coral reefs, with most damage throughout the Indian Ocean and the Western Pacific. This was apparently a 1 in a 1,000 year event in many regions based on the past history of coral reefs in these regions; very old corals around 1000 years old died from bleaching during 1998; and there is no record or memory of similar bleaching mortality in official government records or in the memories of traditional cultures. What is uncertain is whether the major climate shifts
of 1998 will prove to be a 1 in a 1,000 year event in the future. The evidence is strongly against that assumption, with predictions that coral bleaching like that seen in 1998 will become a regular event in approximately 50 years time, although by then most of the susceptible corals may have be lost from many coral reefs. There is a strong probability that some rare and restricted corals may become totally extinct.

Many coral reefs that were severely damaged in 1998 e.g. lost 90% of more of the live coral cover, are now showing remarkably rapid recovery, which has surprised many of observers who found few living corals in the vicinity to repopulate the reefs with new coral larvae. There are reports from GCRMN coordinators in the Arabian/Persian Gulf, Eastern Africa, the Seychelles, Maldives, Palau, Japan and the Great Barrier Reef of rapid recovery from virtually 0-5% coral cover, to 20–30% now. However, this is counterbalanced by poor recovery in areas nearby e.g. Persian/Arabian Gulf and Eastern Africa, as well as the Chagos Archipelago, Sri Lanka, parts of the Philippines, Indonesia and Japan. The recovery is occurring through new coral larvae, as well as regrowth from coral skeletons that were previously considered to be dead. Monitoring is also showing a major shift in the coral populations on these reefs, with the former dominant branching and plating corals (often Acropora species) being replaced by more massive and more resistant species. The reefs that are not recovering well are usually under strong pressures from human activities, especially over-fishing that is removing the algal grazing fishes, excesses of sediment and nutrient pollution, and the damaging practices of bomb and cyanide fishing.

Thus, it is predicted are that most of these reefs will continue to recover and eventually revert to the similar levels of coral cover of reefs pre-1998; provided that there are no repeats of damaging events similar to 1998. Unfortunately, the evidence from the Intergovernmental Panel on Climate Change, NOAA in USA, and other researchers does not provide any confidence, and the authoritative predictions are that coral reefs will continue to suffer from rising levels of global climate change, with increasing sea surface temperatures in the tropics leading to regular bouts of coral bleaching and mortality in summer months.

The current predictions are that the extreme events of 1998 will become more common in the next 50 years (the 1998 event will not be a 1/1000 year event in the future), probably at decadal scales in the first instance and an annual event in 50 years time, with many species lost from coral reefs.

There are several strategies and possible rectifying mechanisms for coral reefs to cope with GCC. The possibility of coral reefs migrating to higher latitudes towards the poles is unlikely, as there are few suitable broad continental shelves in these latitudes and corals rely on photosynthetic energy from their symbiotic zooxanthellae. They will not receive sufficient sunlight energy during the higher latitude winters. The other major mechanism is for corals to adapt or acclimate to rising temperatures, and there is encouraging early evidence, that corals may be able to swap their symbiotic algae for more temperature resistant ones and continue to grow in higher water temperatures.

The other major predicted changes from global climate change are: an increase in the frequency and intensity of tropical storms; more frequent and severe switches in global climate, such that El Niño - La Niña changes will be more regular; a rise in sea level; a potential shift in ocean currents; and an increase in the dissolved concentration of the greenhouse gas, carbon dioxide (CO2) in seawater. There are suggestions that the first effect of more frequent and severe storms has already happened, but clusters like the recent severe storms in the Caribbean are known from historical records and no clear trend has emerged so far. It is apparent that the interval between El Niño events has shortened from about 12 years to less than 7 years, but the record is too short for confirmation. It is also too early to assess whether the large ocean currents will change. Sea level rise will not threaten the coral reefs, but will have potentially disastrous consequences for low coral islands, especially the atoll countries like the Maldives, Tuvalu, Marshall Islands and Kiribati.

One threat from the increase in greenhouse emissions is becoming more likely and could have very serious implications for coral reefs in the future. If the concentrations of CO2 in the seawater continue to rise, there could be serious consequences for all calcifying organisms: tropical corals; cold water corals; calcifying algae; and organisms like foraminifera that are major producers of calcium carbonate in many marine ecosystems.

The ultimate solution to all these global climate change threats to coral reefs and other ecosystems is to reduce the emissions of greenhouse gases that are driving global warming, while simultaneously putting maximal efforts into conserving those coral reefs that have resistance and resilience capacity to warmer waters.
Source: Wilkinson, C. , 2004 , Foreword, Countries, States and Territories Acknowledgements, Co-sponsors and supporters of GCRMN, Introduction and Executive Summary. . p: I-66. in C. Wilkinson (ed.). Status of coral reefs of the world: 2004. Volume 1. Australian Institute of Marine Science, Townsville, Queensland, Australia. 301 p. (See Document)

General (Climate)

2 . Eastern Africa (2002)
New threats have emerged in 2001 and 2002, acting on scales intermediate between between localized anthropogenic stresses, and regional scale climate change. Their direct causation is not yet known, though meso-scale climate changes are likely to be important factors, and the contribution of climate change to changes at this level are currently unknown.
Source: Obura, D. , 2002 , Status of Coral Reefs in East Africa. . in Linden, O., D. Souter, D. Wilhelmsson, and D. Obura (eds.). Coral degradation in the Indian Ocean: Status Report 2002. CORDIO, Department of Biology and Environmental Science, University of Kalmar, Kalmar, Sweden.pp 15-20 (See Document)

General (Climate)

3 . Eastern Africa (2002)
A steady increase of 0.27oC has been measured on S. African coral reefs since in-situ temperature recording began in 1994 (Schleyer & Celliers, this volume). During this time, hard coral cover has increased and soft coral cover remained stable on reef slopes at 12m depth. On reef tops, hard coral cover increased to a lesser extent, and soft coral cover decreased. While bleaching was absent in 1998, it did occur in 2000 associated with elevated temperatures over 28.8oC and clear water conditions. In the short term it appears that warming temperatures may improve conditions for corals in high latitude reefs, especially at depth, however the long term increase in temperatures is likely to be detrimental here
as well. Also important will be the change in water chemistry and pH that may significantly reduce calcification rates of corals.

In addition to the epidemics of planktonic algae and disease, increased occurrence of unusual invertebrate (mantis shrimp) and fish swarms have been reported from East Africa (Richmond et al., in press). Whether these epidemics may be related to oceanographic and monsoon changes influenced by climate change is not yet possible to know, but if so, they are likely to increase in frequency and intensity in coming years, along with the multiple stresses to reef corals that they are associated with.
Source: Obura, D. , 2002 , Status of Coral Reefs in East Africa. . in Linden, O., D. Souter, D. Wilhelmsson, and D. Obura (eds.). Coral degradation in the Indian Ocean: Status Report 2002. CORDIO, Department of Biology and Environmental Science, University of Kalmar, Kalmar, Sweden.pp 15-20 (See Document)

Storms

4 . Pacific (2005)
Tropical Storms

In general, the PRIAs of Johnston, Kingman, Palmyra, Jarvis, Howland, and Baker experience low frequencies of tropical storm events, although occurrences at Johnston are much more common than the other areas. These islands and atolls are located in between the major eastern and western Pacific tropical storm centers, which are most active in late summer and early fall (Figure 12.4). Most storms that develop off the coast of Mexico and head west undergo cyclolysis (storm death) or spin off northwards before reaching the longitude of the PRIAs. Cyclogenesis (storm formation) to the west/northwest of the PRIAs produces tropical depressions and storms that head away from the PRIAs toward the western Pacific. Additionally, due to their proximity to the equator, the U.S. Line and Phoenix Islands are located out of the path of almost all tropical cyclones of any intensity. No tropical cyclones of any magnitude have been observed within the Exclusive Economic Zones (EEZs) of Howland, Baker, or Jarvis Island in the past 60 years. Three cyclones have been observed in the Kingman/Palmyra EEZ. However, only one of these three, Ekeka in 1992, reached wind speeds in excess of 60 knots (Figure 12.4).

Because Johnston is located at a higher latitude than the other areas, it is subjected to a greater degree of tropical storm activity, catching storm systems out of the eastern Pacific center that travel between 10 and 20 degrees latitude. As a result, Johnston experiences a higher frequency of tropical storm events than both the U.S. Line and Phoenix Islands to the south and the NWHI to the north. Significant hurricanes that have passed near Johnston since 1979 include Hurricane John in 1994, Hurricane Keoni in 1993, and Hurricane Keli in 1984 (Figure 12.4).

While the impacts of the tropical storm events on coral reef ecosystems in the PRIAs are not documented, any damage to reef habitats associated with these storms would have been caused primarily by extreme wave energy events. In summary, tripical storms represent a moderately frequent disturbance event experienced by coral reefs at Johnston Island, potentially influencing physical and biological reef structure, although certainly not to the degree experienced by reefs and terrestrial environments in the western Pacific. Kingman, Palmyra, Jarvis, Howland, and Baker, on the other hand, are rarely, if ever, directly subjected to significant tropical storms and hurricanes.
Source: Brainard, R., J. Maragos, R. Schroeder, J. Kenyon, P. Vroom, S. Godwin, R. Hoeke, G. Aeby, R. Moffitt, M. Lammers, J. Gove, M.Timmers, S. Holzwarth, and S. Kolinski , 2005 , The State of Coral Reef Ecosystems of the Pacific Remote Island Areas. . p.338-372 in Waddell, J. (ed.), 2005. The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. NOAA Technical Memorandum NOS NCCOS 11. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team. Silver Spring, MD. 522 pp. (See Document)

General (Climate)

5 . Pacific (2005)
Wave Events

While the direct impacts of tropical storms on the coral reef ecosystems of most of the PRIAs islands and atolls are relatively rare, the impacts of large wave events resulting from distant tropical and extratropical storms may be significant. Episodic events with wave heights around 2-3 m and periods of 15-20 seconds occur at frequent intervals throughout the year in the equatorial PRIAs (Baker, Howland, Jarvis, Palmyra, and Kingman). Although this is an order of magnitude less than NWHI wintertime wave events, the equatorial PRIAs are much less seasonal in terms of wave energy and these relatively more moderate events occur throughout the year (Figure 12.5). These events generally approach this area from the northeast through the northwest during the boreal winter, from the west during the northern hemisphere's typhoon season. The wave climate of Johnston Atoll is likely very similar to that of the NWHI and MHI, with a large number of extremely energetic events in the wintertime and very consistent, moderate waves in the summer.

These episodic wave events subject the shallow-water coral reef communities to a great deal more energy than the average energy level. As such, wave climate likely plays axx fundamental role in forming and maintaining biogeographic (spatial and vertical) distributions of corals, algae, fishes, and invertebrates of the coral reef ecosystems of the PRIAs.
Source: Brainard, R., J. Maragos, R. Schroeder, J. Kenyon, P. Vroom, S. Godwin, R. Hoeke, G. Aeby, R. Moffitt, M. Lammers, J. Gove, M.Timmers, S. Holzwarth, and S. Kolinski , 2005 , The State of Coral Reef Ecosystems of the Pacific Remote Island Areas. . p.338-372 in Waddell, J. (ed.), 2005. The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2005. NOAA Technical Memorandum NOS NCCOS 11. NOAA/NCCOS Center for Coastal Monitoring and Assessment’s Biogeography Team. Silver Spring, MD. 522 pp. (See Document)

Temperature

6 . Southwest Pacific (2008)
Nauru reported coral bleaching and mass fish kills in October-December 2003, possibly due to unusually high sea surface temperatures.
Source: Cherie Morris and Kenneth Mackay (eds.) , 2008 , Status of the Coral Reefs in the South West Pacific: Fiji, New Caledonia, Samoa, Solomon Islands, Tuvalu and Vanuatu . In: Wilkinson, C. (ed.). Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. p177-188. (See Document)

Cyclone

7 . Southwest Pacific (2008)
All countries reported that the greatest threats to coral reefs of the region continued to be human activities and cyclones, with reefs of New Caledonia, Samoa, Solomon Islands and Vanuatu having been damaged by cyclones since the 2004 status report. Cyclone Erica in 2003 destroyed 10-80% of live coral cover on New Caledonia and cyclone Heta struck Samoa in 2004 damaging 13% of the coral reefs. In mid-2004 an unprecedented number of seabirds were found dead on Nauru of unknown causes.
Source: Cherie Morris and Kenneth Mackay (eds.) , 2008 , Status of the Coral Reefs in the South West Pacific: Fiji, New Caledonia, Samoa, Solomon Islands, Tuvalu and Vanuatu . In: Wilkinson, C. (ed.). Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. p177-188. (See Document)

Cyclone

8 . Southeast and Central Pacific (2008)
Cyclones are a prevalent threat in the Cook Islands as they lie on a major cyclone route; in 2005, 5 cyclones hit the Cook archipelago, as well as Niue where the main damage to reefs in the past 30 years has been due to cyclones.
Source: Vieux, C., B. Salvat, Y. Chancerelle, T. Kirata, T. Rongo and E. Cameron , 2008 , Status of Coral Reefs in Polynesia Mana Node Countries: Cook Islands, French Polynesia, Niue, Kiribati, Tonga, Tokelau and Wallis and Futuna . In: Wilkinson, C. (ed.). Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia. p189-198. (See Document)

Temperature

9 . US Pacific Islands (2008)
Global warming is a climate change term used to describe the overall increase in the Earth’s atmospheric and oceanic temperatures over the course of the last century from increased anthropogenic greenhouse gas emissions (primarily carbon dioxide, CO2) from the combustion of fossil fuels (IPCC, 2007). The rapid rate of increase in atmospheric and oceanic temperatures suggests a difference from natural climate variability. Increasing temperatures can lead to changes in sea level, weather patterns, precipitation, storm frequency and magnitude, ocean currents and local biota (IPCC, 2007). The interconnectivity of the Earth’s systems suggests that changes associated with global warming will have many known and unknown cascading effects on ecosystems around the globe (IPCC, 2007).The future effects of increasing temperatures are difficult to quantify due to the unknown and complicated nature of climatic sensitivity, environmental feedback mechanisms and greenhouse gas emissions. Anthropogenic global warming and associated sea level increases may continue for centuries due to the time scales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized (IPCC, 2007). It is predicted that coral reef ecosystems will be under great strain as a result of global warming and climate change (Hoegh-Guldberg, 1999). In addition, projections predict temperature increases and that CO2 will increase beyond levels that reefs have experienced over the past half-million years (Hughes et al., 2003). Two of the major impacts from global warming on coral reef ecosystems are coral reef bleaching and ocean acidification (Kleypas, 2006).



The increase in water temperatures associated with global warming (1-2°C per century), coupled with regionally specific El Niño-Southern Oscillation (ENSO) events, appears to be the main driver of the breakdown between coral-algal symbiotic relationships (coral bleaching) in the Pacific. Reef-building corals are thought to live near their thermal maxima, making them good indicators for changing conditions, and the thermal tolerances of reef-building corals are forecast to be exceeded within the next few decades (Hoegh-Guldberg, 1999). Small increases in water temperature of 1-2°C can stress corals, causing them to expel their symbiotic algae. When these algae, which contain the photosynthetic pigments that give corals their distinct colors, are expelled from coral tissue, the coral looks white or bleached. If the corals are not able to recruit new symbiotic algae in time to fulfill their nutritional needs (which can sometimes take weeks to months), the bleaching can result in mortality of the affected coral.



A major concern is that the accelerating rate of environmental change, including increasing temperatures, could exceed the evolutionary capacity of coral and algal species to acclimate and/or adapt to these changes (Hughes et al., 1993). Bleaching events can stretch across thousands of square kilometers of ocean and immediately cause high levels of coral mortality. In addition, coral bleaching can lead to habitat phase shifts where corals are replaced by other benthic groups, along with changes to the nutrient cycling processes that are thought to be major drivers of high coral reef productivity. Recent research shows that algal-dominated areas occur naturally on many healthy Pacific reef systems (Vroom et al., 2006a). However, algal overgrowth of areas where corals have been reduced by bleaching or other factors can lead to decreased ecosystem health, decreased accumulation of calcium carbonate, and negative impacts to the reef fauna that depend on the structural complexity and food sources provided by corals.



Six major coral bleaching events have occurred since 1979, with massive coral mortality affecting reefs around the globe (Hoegh-Guldberg, 1999). The effect of bleaching events in the PRIA before surveys began in 2000 cannot be determined, and the effects of these events on the PRIA after 2000 are inconclusive. Increasing temperatures associated with global warming are likely to increase the frequency and magnitude of coral bleaching events. The proximity of some of the PRIA to the equator (Howland, Baker and Jarvis Islands) exposes them to some of the greatest changes in temperature during ENSO warming events in the Pacific, and in some cases the islands have experienced conditions that exceed predicted bleaching thresholds (Figure 11.3).
Source: Miller, J., J, Maragos, R. Brainard, J. Asher, B. Vargas-Ángel, J. Kenyon, R. Schroeder, B. Richards, M. Nadon, P. Vroom, A. Hall, E. Keenan, M. Timmers, J. Gove, E. Smith, J. Weiss, E. Lundblad, Scott Ferguson, F. Lichhowski and J. Rooney , 2008 , The State of Coral Reef Ecosystems of the Republic of the Pacific Remote Island Areas. pp. 353-386 . In: J.E. Waddell and A.M. Clarke (eds.), The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2008. NOAA Technical Memorandum NOS NCCOS 73. NOAA/NCCOS Center for Coastal Monitoring and Assessment's Biogeography Team. Silver Spring, MD. 569 pp. (See Document)

Ocean Composition

10 . US Pacific Islands (2008)
The current and projected rates of atmospheric CO2 increase, primarily from the burning of fossil fuels, are estimated at 100 times the rate that has occurred over the past 650,000 years. By the mid-21st century, it is predicted that the increased concentration of atmospheric CO2 will decrease the saturation state of carbonate minerals in tropical ocean waters by 30% and biogenic-carbonate precipitation by 14 to 30% (Kleypas et al., 1999). Coral reef calcification is dependent on the saturation state of carbonate minerals in ocean waters. Reduced carbonate-saturation state promotes dissolution in reef-building corals, and decreased carbonate production makes it more difficult for marine calcifying organisms to form biogenic-carbonate minerals (Orr et al., 2005). Coral reefs are particularly threatened because reef-building organisms secrete metastable forms of carbonate minerals; however, the biogeochemical consequences for calcifying organisms in other marine ecosystems may be equally severe (Kleypas et al., 1999). In addition, the rising atmospheric CO2 levels are irreversible on human timescales (Kleypas et al., 2006). Uptake of CO2 by the ocean helps moderate the rising atmospheric concentrations; however, the associated and linked changes previously described in the oceanic-carbonate-chemistry system increase the concentration of hydrogen ions [H+ ] in solution, resulting in loweredsea-surface pH and "ocean acidification".
Source: Miller, J., J, Maragos, R. Brainard, J. Asher, B. Vargas-Ángel, J. Kenyon, R. Schroeder, B. Richards, M. Nadon, P. Vroom, A. Hall, E. Keenan, M. Timmers, J. Gove, E. Smith, J. Weiss, E. Lundblad, Scott Ferguson, F. Lichhowski and J. Rooney , 2008 , The State of Coral Reef Ecosystems of the Republic of the Pacific Remote Island Areas. pp. 353-386 . In: J.E. Waddell and A.M. Clarke (eds.), The State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2008. NOAA Technical Memorandum NOS NCCOS 73. NOAA/NCCOS Center for Coastal Monitoring and Assessment's Biogeography Team. Silver Spring, MD. 569 pp. (See Document)

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