Coral Reef Ecohydrology Applications

This model was developed for the Great Barrier Reef and successfully verified against an extensive data set. It has also been applied to reefs in Micronesia (Guam, Palau, and Pohnpei).

The people of Micronesia have centuries, as opposed to decades in the Great Barrier Reef, of experience in dealing with coral reefs upon which their livelihood depends. They have traditional management policies that highlight the need to manage human activities that affect coral reef

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Figure 4 Predictions of the along-channel distribution (cell 20, river mouth; cell 1, tidal limit = 60 km) of zooplanktivorous fish biomass in the Guadiana Estuary, Portugal, in 2004, (a) without and (b) with the Alqueva dam. The dam construction was completed in 2003 and in 2004 the dam suppressed all freshets. The 'without dam' calculation assumes natural river hydrographs that were calculated from rainfall data. The 'with dam' calculation uses the observed river runoff as the open boundary condition at the tidal limit. To convert biomass to concentration for fish 2.8 « 2.87 gcm~2.

Figure 4 Predictions of the along-channel distribution (cell 20, river mouth; cell 1, tidal limit = 60 km) of zooplanktivorous fish biomass in the Guadiana Estuary, Portugal, in 2004, (a) without and (b) with the Alqueva dam. The dam construction was completed in 2003 and in 2004 the dam suppressed all freshets. The 'without dam' calculation assumes natural river hydrographs that were calculated from rainfall data. The 'with dam' calculation uses the observed river runoff as the open boundary condition at the tidal limit. To convert biomass to concentration for fish 2.8 « 2.87 gcm~2.

ecosystems. In many islands, the people have direct ownership of coral reefs and the fisheries they support. For Micronesia, the model highlighted the beneficial role of mangroves, and this has resulted in a legislative protection of mangroves in at least one state (Palau). For Guam, Palau, and Pohnpei, the study demonstrated the need for integrating land-use and coral reef management. In islands where some form of traditional leadership still exists, this model has measurably helped in improving local environmental planning because these traditional leaders take into account the long-term, multigenerational impacts of activities in the development of environmental policies. Thus ecohydrology and ecological engineering are accepted and becoming a powerful tool in such islands.

For the Great Barrier Reef of Australia, the model suggests that land use has contributed to the degradation of the health of the Great Barrier Reef and to an increased frequency and intensity of crown-of-thorns starfish infestations. The model also predicts that the health of the Great Barrier Reef will significantly worsen by the year 2050 as a result of global warming. The model demonstrates to managers and politicians that it is worth improving land-use practices to recover the health of the Great Barrier Reef ecosystem. Indeed the model suggests that much-improved land-use practices will enable some regions of the Great Barrier Reef to recover, even with global warming. However, in the longer-term the situation is more gloomy, because the model suggests that if global warming proceeds unchecked only biological adaptation can prevent a collapse of the Great Barrier Reef health by the year 2100.

This ecohydrology model can be used to quantify the effectiveness of remedial measures on land. In theory thus ecological engineers can offer to economists and politicians the hard science data on ecosystem health that are needed to

Figure 5 Predictions of the along-channel distribution (cell 20 = river mouth; cell 1 = tidal limit = 60 km) of phytoplankton biomass for (a) low-flow conditions (2 m3s~1) in summer in the Guadiana Estuary, Portugal, for (b) a hypothetical doubling of the riverine nutrient inflow as a result of planned irrigation farming using Alqueva dam water, and (c) with in addition the removal of the salt marshes. To convert biomass to chlorophyll a concentration 3.5 « 7.8 mg T1.

Distance (cell no.)

Figure 5 Predictions of the along-channel distribution (cell 20 = river mouth; cell 1 = tidal limit = 60 km) of phytoplankton biomass for (a) low-flow conditions (2 m3s~1) in summer in the Guadiana Estuary, Portugal, for (b) a hypothetical doubling of the riverine nutrient inflow as a result of planned irrigation farming using Alqueva dam water, and (c) with in addition the removal of the salt marshes. To convert biomass to chlorophyll a concentration 3.5 « 7.8 mg T1.

Figure 6 Sketch of the dominant physical processes in the coral reef ecohydrology model. A, B, and C represent coral reefs with increasing distance from the coast.

develop management policies that integrate socioeconomics and ecosystem health, as a first step towards planning an ecologically sustainable development. In practice however for the Great Barrier Reef and most corals reefs worldwide outside of a few islands in Micronesia, ecological engineering may have little impact because of two phenomena. Firstly there is the 'tragedy of the commons' where few take any responsibility but everyone has ownership - this is the same problem which has resulted in the collapse of fisheries worldwide. Secondly there is uncertainty in the science of cause and effects of reef degradation - some of that uncertainty is inherent to science, much is purposely manufactured - and this uncertainty helps politicians and decision-makers to justify ignoring the problem and implement no remedial measures.

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