Climate Change and Coral Reefs: Long-term threats, challenges and opportunities

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Climate Change and Coral ReefsLong-term
threats, challenges and opportunities   R.W.
Buddemeier
Presentation to the meeting of the USCRTF San
Juan, Puerto Rico, October 2-3, 2002
Proposals for building on the strengths and
successes of the CRTF, its members, and existing
and new collaborators to successfully address the
global threats to coral reefs posed by climate
change.
With the endorsement and support of the Ocean
Biogeographic Information System (OBIS) and
Census of Marine Life (CoML) programs
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• Carbon Dioxide (CO2) in the atmosphere
• Warms the planet by trapping heat (the greenhouse
  effect)
• Dissolves in the surface ocean water
• -Making it more acidic, which
• -Reduces the concentration of carbonate ion
  (CO3),
• -Slowing the rate of calcification of corals and
  other
• producers of calcium carbonate
• Result two different but interactive reef
  stresses -- acute stress from high temperature
  episodes, plus a growing chronic stress due to
  reduced rates of organism growth and reef
  consolidation
• Illustrations from the NCAR coupled ocean GCM and
  geochemical models.---

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Projecting the future of the marine environment
Scenario B2 was used for the examples in this
presentation -- through 2065, it is the most
conservative of the IPCC Emission Scenario Models
(IPCC 2000) for the time course of atmospheric
CO2.
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Temperature Data
The past 20 years show expansion of the warmest
areas of the Western and Eastern Pacific -- with
short-term high temperature episodes causing
coral bleaching even outside of those areas
1982-1991 Reynolds maximum monthly SST
1992-2001 Reynolds maximum monthly SST
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Model SST results
The geographic distribution of warm areas is
projected to expand over the next few decades --
but to stabilize thereafter.
2000-2009 projected max. monthly SST (pCO2375)
2020-2029 projected max. monthly SST (pCO2415)
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Although some intensification continues in the
western Pacific, tropical oceans have a natural
thermostat that is expected to cap the ranges
and values of the highest temperature classes
2040-2049 projected max. monthly SST (pCO2465)
2060-2069 projected max. monthly SST (pCO2517)
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Calcification controls
Low CaCO3 saturation less calcificationThe
upper right-hand figure represents the low end of
the normal range of conditions experienced by
reefs for the past several million
years. Considerable change has already occurred
(lower right), but reef areas have not yet felt
the full impact.
Preindustrial aragonite saturation state
(pCO2280)
2000-2009 aragonite saturation state (pCO2375)
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As temperatures increase outward from the
equatorial West Pacific and stabilize, favorable
saturation state conditions decrease with an
opposite pattern. The transect of US reef MPAs
in the Pacific provides an ideal network to
monitor, predict and understand the effects of
these unprecedented reef environments.
2020-2029 aragonite saturation state (pCO2415)
2040-2049 aragonite saturation state (pCO2465)
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2060-2069 aragonite saturation state (pCO2517)
Does all marginal mean doom and extinction?
Not necessarily -- there are numerous reef
communities in marginal habitats now. But almost
certainly, the reef communities of the future,
and the management techniques and MPAs they
require, will have structures and functions
different from the ones we now know.
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Necessary steps
Knowledge of species composition and population
structures of reef communities will be critical
for predicting responses to climate change, and
for identifying and managing sustainable systems
Global clines in species richness of corals
(Roberts et al. 2002)
Not all reefs are alike -- gradients of diversity
as well as of environmental conditions provide a
natural laboratory to understand and prepare for
the effects of predictable change.
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Pacific Refuges and Sanctuaries, on a map showing
preindustrial marginality risk and 2060-2069
projected expansion of 18.4 deg isotherm (cool
limit) in green.

• US Pacific refuges and sanctuaries are a network
  of nearly pristine reefs, uniquely situated to
  enable both practical and theoretical
  understanding of the effects of climate change on
  coral reefs.
• USCRTF has the opportunity to add to its existing
  successful activities a long-term commitment to
  adaptive research, monitoring and management that
  will nucleate an unprecedented depth and breadth
  of collaborative work on solving the challenges
  of sustaining coral reef ecosystems.

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Recent announcement NSF 02-186 Biodiversity
Surveys and Inventories, including Planetary
Biodiversity Inventories -- a cooperative effort
of the NSF, the Alfred P. Sloan Foundation, and
the ALL Species Foundation The geographic or
ecological scale of the project should constitute
a natural and compelling biological
focus. Included are very large-scale projects
that can be competed in 5 years or less, and also
longer-term studies PBI attempts to empower
international teams of scientists to intensively
inventory groups across geologic time and
ecological space. Because the oceans that
dominate our planet are so seriously
undersampled, at least one award will be targeted
specifically to a marine group of organisms.
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Supplementary Information Slides
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Addition of IPCC projections to the observed
changes produces an even more dramatic shift for
coming decades

• We have entered a no-analog period of earth
  history
• Trends will continue for decades and are not
  easily reversed
• Accelerated climate change is, or soon will be,
  the overall dominant source of stress for coral
  reefs and other widely-distributed ecosystems

Northern hemisphere temperature history and
projection, 1000-2100 AD
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Generic richness of hermatypic corals. Contours
show max number of genera likely to be found.
(Veron, 1986)
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Figure 4a. Preindustrial marginality risk and
2060-2069 projected expansion of 18.4 deg
isotherm in green.
Figure 4e. 2060-2069 projected marginality risk
(pCO2517)
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Figure 4c. 2010-2019 projected marginality risk
(pCO2387)
Figure 4d. 2020-2029 projected marginality risk
(pCO2415)
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Figure 4e. 2030-2039 projected marginality risk
(pCO2437)
Figure 4f. 2040-2049 projected marginality risk
(pCO2465)
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Figure 4g. 2050-2059 projected marginality risk
(pCO2492)
Figure 4e. 2060-2069 projected marginality risk
(pCO2517)