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. 2012 Mar;22(2):232-261.
doi: 10.1002/aqc.1248.

Reefs and islands of the Chagos Archipelago, Indian Ocean: why it is the world's largest no-take marine protected area

C R C Sheppard  1 , M Ateweberhan  1 , B W Bowen  2 , P Carr  3 , C A Chen  4 , C Clubbe  5 , M T Craig  6 , R Ebinghaus  7 , J Eble  2 , N Fitzsimmons  8 , M R Gaither  2 , C-H Gan  4 , M Gollock  9 , N Guzman  10 , N A J Graham  11 , A Harris  1 , R Jones  9 , S Keshavmurthy  4 , H Koldewey  9 , C G Lundin  12 , J A Mortimer  13 , D Obura  14 , M Pfeiffer  15 , A R G Price  1 , S Purkis  16 , P Raines  17 , J W Readman  18 , B Riegl  16 , A Rogers  19 , M Schleyer  20 , M R D Seaward  21 , A L S Sheppard  1 , J Tamelander  22 , J R Turner  23 , S Visram  4 , C Vogler  24 , S Vogt  25 , H Wolschke  7 , J M-C Yang  4 , S-Y Yang  4 , C Yesson  9
Affiliations

Reefs and islands of the Chagos Archipelago, Indian Ocean: why it is the world's largest no-take marine protected area

C R C Sheppard et al. Aquat Conserv. 2012 Mar.

Abstract

The Chagos Archipelago was designated a no-take marine protected area (MPA) in 2010; it covers 550 000 km2, with more than 60 000 km2 shallow limestone platform and reefs. This has doubled the global cover of such MPAs.It contains 25-50% of the Indian Ocean reef area remaining in excellent condition, as well as the world's largest contiguous undamaged reef area. It has suffered from warming episodes, but after the most severe mortality event of 1998, coral cover was restored after 10 years.Coral reef fishes are orders of magnitude more abundant than in other Indian Ocean locations, regardless of whether the latter are fished or protected.Coral diseases are extremely low, and no invasive marine species are known.Genetically, Chagos marine species are part of the Western Indian Ocean, and Chagos serves as a 'stepping-stone' in the ocean.The no-take MPA extends to the 200 nm boundary, and. includes 86 unfished seamounts and 243 deep knolls as well as encompassing important pelagic species.On the larger islands, native plants, coconut crabs, bird and turtle colonies were largely destroyed in plantation times, but several smaller islands are in relatively undamaged state.There are now 10 'important bird areas', coconut crab density is high and numbers of green and hawksbill turtles are recovering.Diego Garcia atoll contains a military facility; this atoll contains one Ramsar site and several 'strict nature reserves'. Pollutant monitoring shows it to be the least polluted inhabited atoll in the world. Today, strict environmental regulations are enforced.Shoreline erosion is significant in many places. Its economic cost in the inhabited part of Diego Garcia is very high, but all islands are vulnerable.Chagos is ideally situated for several monitoring programmes, and use is increasingly being made of the archipelago for this purpose.

Keywords: British Indian Ocean Territory; Chagos; coral recovery; fisheries; island conservation; marine invasives; marine protected area; reef disease; reef fishes; seamounts.

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Figures

Figure 1
Figure 1
The Chagos Archipelago. Inset shows location and MPA boundary (circular shape with flattened northern border). Main map: the five atolls with land are shown in bold, the islands on Great Chagos Bank and submerged reefs and atolls are not bold. All are located in the central area of the MPA.
Figure 2
Figure 2
a) island areas in the Chagos Archipelago (scale in ha). The largest islands are named. b) area of submerged substrate in the archipelago (scale in km2) (from Dumbraveanu and Sheppard, 1999).
Figure 3
Figure 3
Percentage coral on reefs by the main coral types in 4 years, for the major live categories identifiable by snorkelling in 1999. Arrows along the top are dates and approximate relative severity (arrow thickness) of previous warming events (from Sheppard, 1999a).
Figure 4
Figure 4
Coral cover in depths to 25 m on ocean-facing slopes in different years (Sheppard 1980a, , ; Sheppard et al., 2008; Sheppard unpublished data). Data are of all ocean-facing transects in this series measured on each date. Bars are error bars (error data lost for 1978).
Figure 5
Figure 5
Mean percentage cover values of life form and substrate categories pooled from all depths and all sites for each of four atolls (GCB:Great Chagos Bank, DG: Diego Garcia, SAL: Salomon atoll, PB: Peros Banhos atoll), surveyed by video during 2006. Bars are error bars.
Figure 6
Figure 6
Change in reef fish species richness across seven countries in the Indian Ocean following the 1998 coral mortality event. Chagos sites represented by filled circles. Adapted from Graham et al. (2008).
Figure 7
Figure 7
Percentage of adult colonies in different atolls showing disease or other adverse conditions. Bars are standard error bars.
Figure 8
Figure 8
Percentage of reefs in different categories in the Indian Ocean. Categories are those from Wilkinson (2008a). The probable proportion occupied by Chagos (solid line to vertical) is about half of the reefs in the ‘best’ category. From the dashed line to vertical is an alternative estimate of the proportion of Chagos reefs according to Spalding using slightly different categories (pers. comm.).
Figure 9
Figure 9
Seamounts of the Chagos MPA as identified in Yesson et al. (2011). Bathymetry data from shuttle radar topography mission 30 arc-second grid (http://www2.jpl.nasa.gov/srtm/).
Figure 10
Figure 10
The median lifetime displacement of skipjack (red) and yellowfin tuna (yellow), superimposed on a map of the Chagos MPA
Figure 11
Figure 11
Reef substrate or limestone banks within the photic zone in the central and western Indian Ocean.
Figure 12
Figure 12
(a) Crown of thorns genetic groupings. (b) peacock hind (Cephalopholis argus). (c) brown surgeonfish (Acanthurus nigrofuscus). (d) coconut crab (Birgus latro). Colour coding for the crown of thorns (Vogler et al., 2008, in prep.) and peacock hind (Gaither et al., 2011) indicate distinct genetic lineages. Dashed lines for the brown surgeonfish (Eble et al., 2011) indicate genetically independent populations. Photo credit: www.aquaportail.com. Image 12(b) and 12(c) reprinted from Gaither et al. (2011) and Eble et al. (2011) with permission from the authors. For (d) solidity of arrow lines represents relative amounts of gene flow, so that for this terrestrial crab flow is mainly eastwards during the Equatorial Counter Current flow.
Figure 13
Figure 13
Map of Diego Garcia atoll. The military facility is on the western arm. Gray line shows the Ramsar site, which encompasses most of the lagoon, extending seaward on the eastern side. The eastern arm south approximately to the line where the Ramsar boundary intersects the coast is a ‘Nature Reserve’ which covers land only. From the top of the eastern arm to the line marked ‘A’, plus the three circled islets in the mouth of the atoll, are ‘Strict Nature Reserves’, which each cover land plus the sea area extending out 200 m from shore.
Figure 14
Figure 14
Cross-sections of (a) Sipaille, (b) Lubine, (c) Sudest islands in Egmont atoll, (d) Isle de Coin on Peros Banhos atoll, and (e) Ile Boddam on Salomon atoll. Y-axis is metres above mean high tide in (a)–(c), and from a relative datum in (d)–(e). (a) Lagoon is on right, total width is 500 m, (b) lagoon on right, total width 450 m, (c) lagoon is on left, total width 250 m. (d) and (e) have no horizontal dimensions but are larger islands. Solid horizontal lines are mean high water springs. (a)–(c) from Sheppard (2002), (d)–(e) from Royal Haskoning (2002). Dashed lines in (d)–(e) are estimated flooding levels following severe storm overtopping.
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