climate change and coral reefs: long-term threats, challenges and opportunities r.w. buddemeier

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

R.W. Buddemeier

Presentation to the meeting of the USCRTFSan 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

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.---

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.

Projecting the future of the marine environment

1982-1991 Reynolds maximum monthly SST

1992-2001 Reynolds maximum monthly SST

The past 20 years showexpansion of the warmest areas of the Western and Eastern Pacific -- with short-term high temperature episodes causing coral bleaching even outside of those areas

Temperature Data

2020-2029 projected max. monthly SST (pCO2=415)


The geographic distribution of warm areas is projected to expand over the next few decades -- but to stabilize thereafter….

Model SST results



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

Preindustrial aragonite saturation state (pCO2=280)

2000-2009 aragonite saturation state (pCO2=375)

Low CaCO3 saturation = less calcification

The 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.

Calcification controls



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.


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.

Global clines in species richness of corals (Roberts et al. 2002)

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

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.

Necessary steps

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.

Recent announcement: NSF 02-186Biodiversity 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.”

Supplementary Information Slides

Northern hemisphere temperature history and projection, 1000-2100 AD

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

Generic richness of hermatypic corals. Contours show max number of genera likely to be found.

(Veron, 1986)

Figure 4a. Preindustrial marginality risk and 2060-2069 projected expansion of 18.4 deg isotherm in green.

Figure 4e. 2060-2069 projected marginality risk (pCO2=517)

Figure 4c. 2010-2019 projected marginality risk (pCO2=387)

Figure 4d. 2020-2029 projected marginality risk (pCO2=415)


Figure 4f. 2040-2049 projected marginality risk (pCO2=465)

Figure 4g. 2050-2059 projected marginality risk (pCO2=492)


climate change and coral reefs: long-term threats, challenges and opportunities r.w. buddemeier

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