Reefs as Habitats or Habitats for Reefs: Global-Scale Coral Reef Biogeography

1. Reefs as Habitats or Habitats for Reefs:Global-Scale Coral Reef Biogeography Robert W. Buddemeier Casey J. McLaughlin Peder Sandhei Kansas Geological Survey and Department of Geography, University of Kansas Acknowledgements: J. A. Kleypas, J.-P. Gattuso, B. A. Maxwell, D. G. Fautin, J. D. Bartley Support: NSF OCE-00-03970, ‘Biogeoinformatics of the Hexacorallia;’ National Coral Reef Insititute; IGBP-LOICZ; UNEP-GEF

2. Key Issues --- • What are the emergent properties of coral reefs, communities, and organisms when considered across multiple (large) scales of space and time? • How may these properties help us understand functioning, occurrence, history and probable future of such features? • What does this understanding tell us about priorities for research and management? Conceptual approach: Consider that reefs and communities have – and require – habitats or niches that overlap with but are not identical to the habitats or niches that these reefs and communities provide for the constituent organisms --- which are in most cases not unique to ‘reefs’ (sensu stricto).

3. Preview of Coming Attractions ---- Coral Reefs 21(1), 2002 – “Large-scale dynamics” issue • Emergent patterns from the contributed papers: • Community composition, structure, organismal biogeography: • Exhibit weak latitudinal gradients within the tropics; • Exhibit strong extratropical latitudinal gradients; • Exhibit very strong onshore-offshore (land-ocean) gradients • The land-ocean distinction is critical in considering the nature and synergism of forcing functions of environmental change.

4. Changes in land-based stress are closely related to human population and land-use Geospatial clustering provides classifications of coastal zone population density and related variables – first-order proxies for ‘onshore reef’ anthropogenic stresses

5. The inverse question – where might we find relatively pristine coastal environments for ‘baseline’ samples or possible preservation? • With polar regions cropped, filter data for population density <10/km2, land cover < 5% cropland, then cluster • -- Areas of probable human impact disappear

6. Too stringent? Too depressing? Relax the standards – to population density <100/km2 and <10% cropland Most of Asia, all of Florida is still “gone” – How do land-based stresses compare to and interact with more generalizable oceanic/climatic stresses?

7. Global surface temperature, observed and projected from IPCC scenarios The maximum temperature excursions of the late 1990s could be the mean conditions by 2010, and the lower limit of variation by 2020 – nearshore, short-term variability is likely to be higher than the global and oceanic.

8. Aragonite saturation state – “Holocene normal,’ with arbitrary but informed estimates of how much reef calcifiers care -- greener is better

9. Oceanic saturation states now – still green, but not as dark (nearshore values are likely to be different, probably lower)

10. With a doubled atmospheric CO2 concentration, wide areas remain ‘tolerable,’ few ‘good’ – how do these overlay with the human-derived near-shore stresses and other climatic factors?

11. 2065 Aragonite saturation: Green = good, tan = marginal 2040-2060 mean ann. SST, w/present (gray line) and future (pink) 29o contour Low-moderate pop. density, ag land use -- present values In the Indo-West Pacific -- Australia, East Africa/Red Sea, and islands in the subequatorial southern hemisphere tropics look like the best bets from a pessimistic ‘triage’ viewpoint What science-related questions and conclusions can we develop to tell us how justified the pessimism is?

12. Conclusions -- Observations • There are essentially no pristine areas or true baselines available: We have to infer the rates, directions, and mechanisms of change from ‘long-term’ (on a human scale!) or large-scale studies. • There is great – and largely unexploited – potential for integration and understanding in the intermediate- and large-scale patterns of (a) community structure and biogeographic organism distribution and (b) community and organism metabolism. • [see also: OS32J-06, OS42C-140, OS42C-141]

13. Editorial Conclusions – Needs and Opportunities • Community-habitat classification: what community types are distinguishable on the basis of control by environmental parameters; what are appropriate assessment scales? • 2. Organism-habitat classification: where are the reef organisms when there aren’t any reefs, and what does this imply for persistence and recovery at various scales? • 3. Adaptation and acclimatization: what are the mechanisms, rates, and appropriate definitions at the organism level, and how do these interact to produce community scale analogs (e.g, replacement, with functional continuity)?