Ridge to Reef Management Approaches

Synopsis from the International Coral Reef Symposium, Session on Ridge to Reef Management Approaches

By Christopher Brown

A globally significant threat to coastal reef ecosystems is the run-off of pollutants from on land.  Ridge to reef planning takes into account these pollutants when creating management plans for coral reefs (e.g. this work in Fiji).

Ridge to reef management is made challenging by the difficulty of observing linkages from ecosystems on land to those in the sea. This observation challenge means it can be difficult to communicate the importance of ridge to reef approaches to the public. However, even when the impacts are obvious, such as widespread public concern over sediment plumes on Hawaii’s coast, it is difficult to trace the pollution back to its source.

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Management needs to know where pollutants come from so they can priortise limited resources for taking actions to remediate pollutation, or avoid future pollutants.

The nascent sub-field of ‘ridge to reef management’ is tackling these observation and communication challenges. The session on Ridge to Reef Management Approaches at the International Coral Reef Symposium in Hawaii approaches covered the cutting edge in this field.

At the session I learned that many nations are just begining  to develop ridge to reef plans. To predict the impacts of land-use change, most groups are linking existing tools, such as sediment run-off models, oceanographic models and coral reef surveys.

Current efforts to create ridge to reef plans included Cuba (F Pina Amargos, Universidad de la Habana), El Nido in The Philippines (B Carino-Valdez, University of Philippines), American Samoa (Alice Lawrence,  Department of Marine and Wildlife Resources), Puerto Rico and Hawai’i (David Whitall, NOAA National Centers for Coastal Ocean Science), West Maui in Hawaii (Bernardo Vargas-Angel, University of Hawaii, NOAA), Lāna’i Island Hawaii (Lida Teneva, Conservation International) Papua New Guinea (Viv Tulloch, University of Queensland), Hawaii as a whole (Kim Falinski, University of Hawaii), and finally our efforts in Fiji (with the Wildlife Conservation Society).

In most of these regions the focus was on existing run-off impacts. Therefore the focus of actions was on identifying priorities for restoration, rather than protecting forest from future degradation.

For instance, much of the work in Hawaii was focussed on run-off from agricultural land and associated roads. Given management agencies have limited budgets for restoration actions, the hope is that science can identify priority areas for restoring land or repairing roads.

Several speakers were also looking at the impacts of future expected land-uses. For instance, Viv Tulloch has modelled the impacts of future oil palm plantations on coastal ecosystems on New Ireland, Papua New Guinea (paper in press with Biological Conservation). She found that current ‘sustainable’ guidelines for oil palm development may have severe impacts on coral reefs. Her work suggests protecting reefs requires more stringent restrictions on where oil palm can be developed.

Many of these regions have limited historical data for documenting ridge to reef impacts. Therefore, many of the talks focussed on methods that can be used in data limited situations.

As an example, Kim Falinski from University of Hawaii has compiled available data on soils and runoff for all the Hawaiian islands. The hope is that this data can be used to inform future planning efforts. She has also modified existing models for sediment run-off to be used in data-limited regions (paper currently under review).

As another example, I have developed a new Bayesian modelling tool that can be used to trace pollutants from reefs back to their source catchments (paper currently under review). This is useful for ridge to reef planning because we can identify the catchments that are having the greatest impact on reef ecosystems. The tool can be applied with freely available global satellite data-sets, so can be used in data-poor areas.

Methods to fill in  gaps about the impacts of past land-use change on reefs was also highlighted in several talks. For instance Jessica Carilli (University of Massachussets) is using geo-chemical records from coral cores to document the historic impacts of land-use change and determine whether observed coral reef declines may have been caused by land-use change.

Understanding whether ridge to reef planning can benefit reefs requires monitoring of existing efforts. Several speakers have been monitoring existing ridge to reef plans.

For instance, there has been over a decade of ridge to reef planning for the catchments that feed into Australia’s Great Barrier Reef. Britta Schaffelke (Australian Institute of Marine Science) spoke about the challenge of identifying appropriate indicators to monitor whether the management is working. She highlighted the importance of extreme events, especially cyclones and noted that they may often mask the benefits of improved land-use practices.

In Hawaii Lida Teneva (Conservation International) is performing small-scale management experiments to inform on efforts to avoid sediment run-off to reef flats. They are monitoring control and impact sites on reefs to determine the effectiveness of small dams for stopping sediment run-off to reef flats. Such management experiments are rare, but important to progress ridge to reef planning.

A final insight that emerged in the sessions was the pollutant threats, and consequently optimal management actions, in most regions were highly context specific. David Whitall (NOAA National Centers for Coastal Ocean Science) is conducting research across many of the US’s tropical islands and finding that the watersheds are very all different – even when pollution stresses are similar, the impacts to reefs up vary because of varying geography.

This variability in impacts is a challenge for ridge to reef planning which is often operating in data poor regions. Therefore, further development of  methods for data poor regions, and cost effective methods for filling in historical data gaps, which were highlighted in this symposium, are priorities for future research.

Authors note: Two years later we have completed our “Ridge to Reef Fisheries” working group and solved some of the above problems. You can read more here.




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