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Green Zones are proving to be effective at maintaining sustainable populations of target fish species - they may also play a large role in maintaining a healthy ecosystem in the face of increasing pressures, such as climate change.
No-take marine reserves (green zones) are increasingly being established to conserve or restore marine ecosystems and biodiversity and to increase the sustainability of exploited fish populations. Zoning management plans; including networks of no-take marine reserves (green zones), were first implemented in the Great Barrier Reef Marine Park (GBRMP) in the late 1980's. Under the original zoning plans, approximately 5% of the marine park area and 25% of the coral reefs were designated as green zones. An increased appreciation of the current and future threats to the GBRMP ecosystem, strong national support for increased protection and sufficient political will, led to the establishment of a new zoning plan in 2004 that included a large number of new green zones. Under the new zoning plan, approximately 33% of the marine park area (and 33% of the reefs) is protected within green zones. The need to objectively assess the ecological and sociological implications of zoning management is widely acknowledged and it has attracted an increasing amount of research effort in recent years. Critical knowledge gaps still remain however, and research being conducted by our group is focused on determining how and to what extent networks of green zones may help to protect biodiversity, sustain stocks of fished species and increase ecosystem resilience.
We established a long-term monitoring program between 1999 and 2004, with the primary objective of providing a robust assessment of the ecological effects of zoning management on inshore coral reefs of the GBRMP. The project uses underwater visual surveys to document the status of reef fish and benthic (coral) communities and to quantify long-term changes in these communities due to management zoning, climatic disturbances (eg. cyclones and river flood plumes) and outbreaks of coral diseases and coral predators (COTS, Drupella sp.). The project has provided clear evidence that GBRMP green zones have led to significant enhancement of populations of fishery targeted species such as coral trout (Plectropomus spp.). It has also established the basis for effectively assessing the potential contribution of the GBRMP green zone networks to conserving biodiversity and mitigating against the escalating effects of climate change.
Since 2007 we have also been conducting research that employs high-resolution DNA analyses and biophysical modeling to track the dispersal patterns of larvae from the reefs on which they are spawned to the reefs on which the settle as juveniles and grow to join the adult populations. The research has shown that a high proportion of coral trout larvae are dispersing to reefs less than 30km from those on which their parents were located. A key finding of the research is that adult coral trout within green zones are supplying significant numbers of recruits (juvenile fish) to surrounding reefs that are open to fishing. Between 2007 and 2009, the green zones in the Keppel Islands (28% of the total reef area) were providing at least 50% of the total coral trout and stripey snapper recruitment to all local reefs within the approximately 1000km2 study area. The research findings to date provide the first compelling evidence that the GBRMP green zone network has enhanced the productivity and sustainability of exploited fish populations and that the benefits of protection are extending to current and future generations of recreational and commercial fishers. This research is currently being expanded to a broader region of the southern GBRMP.
Harrison H.B., Williamson D.H., Evans R.D., Almany G.R., Thorrold S.R., Russ G.R., Feldheim K.A., van Herwerden L., Planes S., Srinivasan M., Berumen M.L. & Jones G.P. (2012). Larval Export From Marine Reserves and the Recruitment Benefit for Fish and Fisheries. Current Biology 22: 1023-1028.
McCook L.J., Ayling T., Cappo M., Choat J.H., Evans R.D., Freitas D.M., De, Heupel M., Hughes T.P., Jones G.P., Mapstone B., Marsh H., Mills M., Molloy F., Pitcher C.R., Pressey R.L., Russ G.R., Sutton S., Sweatman H., Tobin R., Wachenfeld D.R., Williamson D.H. (2010). Adaptive management of the Great Barrier Reef: a globally significant demonstration of the benefits of networks of marine reserves. Proc Natl Acad Sci USA 107: 18278-18285.
Russ G.R., Cheal A.J., Dolman A.M., Emslie M.J., Evans R.D., Miller I., Sweatman H. & Williamson D.H. (2008). Rapid increase in fish numbers follows creation of world's largest marine reserve network. Current Biology 18: 514-515.
Williamson D.H., Russ G.R. & Ayling A.M. (2004). No-take marine reserves increase abundance and biomass of reef fish on inshore fringing reefs of the Great Barrier Reef. Environmental Conservation 31(2): 149-159.