Download Biological Impacts: Threat to Coral Reefs

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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