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& Climate Change Threat to Coral Reefs Ryan Bailey Nikhita Cambronero Environmental Changes Coral reefs, both tropical and deep cold water, are diverse marine ecosystems. Coral reefs are in danger. Damaged by a combination of direct human impacts and global climate change. Strong international consensus of global climate change. credit: NOAA, NASA, Reef Check, UNEP, Reef Relief, Australian Government, University of Texas Rate of climate change is increasing. Before industrial revolution, the atmosphere contained about 280 ppm of CO2; today it is 35% higher (>380ppm) and the increase in CO2 continues to accelerate faster than predicted. Sofar2go.org “Coral reefs are the world’s most diverse marine ecosystems and are critical for the livelihoods of millions of people who depend on them. Despite this, the health of many coral reefs has declined for decades due to many local stresses; now climate change has the potential to devastate coral reefs around the world. Warming temperatures and ocean acidification are already affecting coral reefs, causing frequent bleaching events and slowing the formation of coral skeletons. We can avoid catastrophic damage to coral reefs but to do so means we must reduce both climate change and local threats. All available evidence suggests that time is running out and that soon conditions on the planet will be so severe that coral reefs will no longer thrive.” (Status of Coral Reefs of the World: 2008) References: The manuscript contents are solely the opinions of the authors and do not constitute a statement of policy, decision, or position on behalf of NOAA or the US Government. C. Mark Eakin, Coral Reef Watch, National Oceanic and Atmospheric Administration, [email protected]; Joan Kleypas, National Center for Atmospheric Research Boulder, Colorado, USA, [email protected]; Ove Hoegh-Guldberg, Centre for Marine Studies, University of Queensland, Australia. [email protected]. Wilkinson C, Souter D (eds) (2008), Status of Caribbean Coral Reefs after Bleaching and Hurricanes in 2005. Global Coral Reef Monitoring Network, and Reef and Rainforest Research Centre, Townsville, Australia. 148 pp. Top 10 Threats to Coral Reefs Global Change Threats: •Coral Bleaching •Rising levels of CO2 •Diseases, Plagues and Invasives •Direct Human Pressures: •Over-fishing & destructive fishing •Sediments •Nutrients •Development Inadequate Governance, Awareness and Political Will: •Poor management capacity •Rising power & growing populations •Law Political Will Bryant et. Al., Reefs at Risk: a Map-Based Indicator of Threats to the Worl’d’s Coral Reefs, World Resources Institute (WRI), Washington DC, 1998 Sadly, continuing human stresses on coral reefs are still present. The global change threats are 1) coral bleaching from warmer seawater due to global climate change; 2) rising concentrations of dissolved CO2, also a product of global change; 3) diseases, plagues and invasive species. There are also direct human pressures which include: 4: excess sediments flowing off the land; 5) pollution by nutrients and chemicals, arising from poor land management, agriculture and industry; 6) over-fishing and destructive fishing, especially taking algal grazing fishes, the ‘immune system’ of a coral reef; 7) unsustainable and destructive development of costal areas. The graph shows threats to world’s coral reefs which include tourism, poison fishing, overexploitation, sedimentation, coral harvesting dynamite fishing and pollution. This graph shows the various acitivities that are affecting the reefs. “The graphic ‘Major Threats to Reefs’ shows percentage of reefs that are threatened by overexploitation, coastal development, inland pollution and marine pollution, and the degree to which they are under threat. The graphic ‘Destroyed Coral Reefs’ show the percentage of coral reefs that have been destroyed in the world’s major regions.” References: The manuscript contents are solely the opinions of the authors and do not constitute a statement of policy, decision, or position on behalf of NOAA or the US Government. C. Mark Eakin, Coral Reef Watch, National Oceanic and Atmospheric Administration, [email protected]; Joan Kleypas, National Center for Atmospheric Research Boulder, Colorado, USA, [email protected]; Ove Hoegh-Guldberg, Centre for Marine Studies, University of Queensland, Australia. [email protected]. Wilkinson, Clive. Global Coral Reef Monitoring Network Bryant et. Al., Reefs at Risk: a Map-Based Indicator of Threats to the Worl’d’s Coral Reefs, World Resources Institute (WRI), Washington DC, 1998 Coral Bleaching Coral bleaching results when the symbiotic zooxanthellae (single-celled algae) are released from the original host coral organism due to stress. High temperatures speed up normal photosynthetic process, which produce toxic free oxygen radicals. Stress increases vulnerability of coral diseases and reduces corals’ ability reproduce. (Status of Coral Reefs of the World: 2008) • Hey! Coral bleaching results when the symbiotic zooxanthellae are released from the original host coral organism due to stress. When the zooxanthellae are expelled, the coral loses its pigment, leading to a bleached or complete white appearance. Toxins are produced when water temperatures rise. The world has lost about a fifth of its corals and many of the remaining reefs could die in the next 20 to 40 years unless greenhouse gas emissions are reduced. “Further coral loss will have alarming consequences for some 500 million people who depend on reefs for their livelihood” -Global Coral Reef Monitoring Network (GCRMN). If nothing is done to substantially cut emissions, we could lose coral reefs forever. The impacts of climate threats, such as rising sea surface temperatures and seawater acidification, is being strengthened by other negative factors like over fishing, pollution and invasive species. “As emissions of the greenhouse gas carbon dioxide increase, oceans absorb more of them and become more acidic, and this is damaging a wide range of marine life from corals to plankton.” References: Scientific America, Climate change may cause more coral extinction: study”, accessed 23 February 2009 Science Daily. Coral Bleaching. Accessed 23 February 2009 Ocean Acidification Acidification due to climate change: Impacts for oceans & coral reefs: Process: ocean uptake of CO2 from the atmosphere reduces the severity of the GHG effect and climate change (and the temperatures that cause coral bleaching). Sadly, increase CO2 alters chemistry of seawater and lowers pH (a lower pH means more acidic via a higher concentration of hydrogen ions). (Status of Coral Reefs of the World: 2008) Credit: UNEP/GRID-Arendal 2008 “Acidification due to climate change-impacts for oceans and coral reefs. “As carbon concentrations in the atmosphere increase from land use changes and emissions from fossil fuels- so do concentrations in the ocean.” This results in a chemical process creating acidification. "The impacts will be greatest at high latitudes. This will have an impact on all marine organisms with calcerous shells and body parts, in addition to coral reefs this includes shellfish and plankton.” (Status of Coral Reefs of the World: 2008). “Scientists are highly confident that the increases in human-caused GHGs in the atmosphere over the last century have caused most of the 0.7°C (1.3°F) rise in the average global temperature of the surface ocean, and the 0.5°C (0.9°F) rise in tropical coral reef water temperatures. The ocean absorbs between one-quarter and one-third of the CO2 that is added to the atmosphere each year resulting in ‘ocean acidification’ from carbonic acid made by increasing concentrations of dissolved CO2 in seawater. Average global ocean pH has already dropped from around 8.2 to 8.1” (Status of Coral Reefs of the World: 2008). References: Scott Heron, William Skirving, Mark Eakin. Global Climate Change and Coral Reefs: Status of Coral Reefs of the World 2008. Accessed 23 February 2009 Rising Sea Surface Temperatures First major marine ecosystems in the world to be seriously damaged by global climate change. When sea surface temperatures exceed the summer maximum by more than 1C for 4 weeks or more under clear tropical skies, corals begin to bleach. Thermal stress & low adaptive capacity. Current predictions are that corals will not adapt to warmer water without stabilization or decrease in GHGs. How are temperature increases and ocean acidification acting together to threaten coral reefs? Scenarios for climate change UNEP/GRID-Arendal 2008 UNEP/GRID-Arendal 2008 Scenarios for bleaching events “Water temperatures over the past century have risen on coral reefs in all global regions. The largest increases have been in the Indian Ocean, symbolised by the massive coral bleaching there in 1998. Thermal stress records show a high degree of correlation with widespread and severe coral bleaching observed on coral reefs around the world in recent years. Moreover, with predictions of continued warming, the outlook for corals around the world is one of repeated large-scale bleaching events. The question that remains is how successfully corals and reef ecosystems can acclimate and adapt to these future warm conditions.” (Status of Coral Reefs of the World: 2008) “Tropical sea temperature rises and coral reefs - climate change scenarios. The impacts of coral reefs from rising sea temperatures. When coral reefs become heat-exposed they die, leaving the white dead coral, also known as bleaching. With even moderate pollution, the coral are easily overgrown with algae, or broken down by wave activity or storms, leaving only “coral rubble” on the ocean bed.”* “Climate change and tropical coral reefs, scenarios for bleaching events Projected areas of above normal sea temperature where coral bleaching is likely to occur for the SRES A2 scenario (continuing current trends) by two different models, the PCM (1.7°C increase in 100 years) and the HadCM3 (3°C increase in 100 years) by approximately 2035 (left) and by 2055 (right). Both models project severe annual bleaching in more than 80% of the Worlds coral reefs by 2080.”* References: Scott Heron, William Skirving, Mark Eakin. Global Climate Change and Coral Reefs: Status of Coral Reefs of the World 2008. Accessed 23 February 2009 *Donner, S.D., Skirving, W.J., Little, C.M., Hoegh-Guldberg, O., Oppenheimer, M. 2005. Global assessment of coral bleaching and required rates of adaptation under climate change. Global Change Biology vol, 11, 2251-2265. Limit Climate Change Impacts Better Governance •Improve awareness and communication •Multilateral Environment Agreements •Assist developing countries to implement agreements Integrated Coastal Management •Reduce sediments, sewage 3 Actions to help: •Reduce GHG’s emissions •Maintain resilience •Increased investment in research on reef restoration credit: NOAA, NASA, Reef Check, UNEP, Reef Relief, Australian Government, University of Texas “Action to conserve reefs is now urgent and must include: strong policies to reduce greenhouse gases emissions; effective management of local stresses; and research to improve conservation and restoration efforts. Only through such concerted action will corals survive the next to centuries as temperatures continue to rise” (Global Climate Change and Coral Reefs: Rising Temperatures, Acidification and the Need for Resilient Reefs). There are several actions required to limit climate change impacts on coral reefs. This would include strong policies to reduce greenhouse gas emissions; effective management of local stresses; and research to improve conservation and restoration efforts. Only through such concerted action will corals survive the next two centuries as temperatures continue to rise. (Global Climate Change and Coral Reefs: Rising Temperatures, Acidification and the Need for Resilient Reefs). References: The manuscript contents are solely the opinions of the authors and do not constitute a statement of policy, decision, or position on behalf of NOAA or the US Government. C. Mark Eakin, Coral Reef Watch, National Oceanic and Atmospheric Administration, [email protected]; Joan Kleypas, National Center for Atmospheric Research Boulder, Colorado, USA, [email protected]; Ove Hoegh-Guldberg, Centre for Marine Studies, University of Queensland, Australia. [email protected]. Wilkinson, Clive. Global Coral Reef Monitoring Network