Natural Disasters – Positive or Negative For Our Coral Reef EcoSystem?
A natural disaster is usually one of the factors that balance the natural ecosystem of any given environment. It usually gives all the living species in any given environment a fresh start, to some species; the natural disaster influence can be beneficial and detrimental especially on the marine ecosystem. Tropical climates have the favorable conditions for most coral species for growth and hence are home to millions of fish species. However, the tropical zone weather conditions can also lead to dangerous and life threatening disasters, including cyclones, floods, droughts, earthquakes and tsunamis.
Fiji lies in the area occasionally traversed by tropical cyclones. They are mostly confined to the period November to April, with greatest frequency around January and February. On average, some ten to twelve cyclones per decade affect some part of Fiji, and two or three causing severe damage. Specific locations may not be directly affected for several years but the dominant north-west tracks give some increased risk of damage in the outlying north-west island groups. During the cyclone period, there is a risk of strong winds, heavy rains, flooding, landslides and road closure.
Tropical cyclones with extreme weather can drastically impact the marine ecosystem especially on the coral reefs, solitary reef fish, ornamental fish, endemic and endangered marine species, and sea grass beds. In 2010-11, in the Great Barrier Reef Marine Park, flood plumes and Cyclone Yasi caused severe and widespread damage to the marine park where six percent of the park was reported to be greatly damaged with broken corals in an area exceeding 89000 kilometers square. In 2012, Cyclone Evan unleashed winds of up to 230kmh (145mph) on Fiji’s main island, as well as the west and northwest.
MES staff conducted reef assessment (Reef Check) to most of its resort stakeholders and stated that the worst affected inshore reefs were reduced to extensive rubble fields. On the worst affected outer- shelf reefs, more than half of the surface of crests and outer slopes were stripped off their framework down to solid substratum approximately 0.5 metres below previous living coral surface. Coral breakage and dislodgement of massive corals were common events. In many areas, strong currents had moved rubble and sand, accumulating in reef gutters and sometimes scarring or burying corals, and exposing previously buried reef. Beds of rubbles or fields of massive boulders came to rest on soft sediment on the leeward sides. The “branching coral” (e.g. Acropora spp) are mostly affected compared to some “massive” or “boulder-like” (e.g.Porites spp) which tend to withstand the impacts of strong wave actions. Decrease in fish abundance are evidently observed on affected reef as there shelter and food supplies are damaged or even destroyed.
Very often the perspective natural disasters (cyclone) are only destructive and disastrous events. However, they also provide ecological benefits to tropical and sub-tropical environments. Rainfall gives a boost to wetlands and flushes out lagoons, removing waste and weeds. Cyclone strong winds and waves move sediment from bays into marsh areas, revitalizing nutrients supplies. While there is always the potential for mechanical damage, coral reefs also receive benefit from cyclone during the warm summer month. In addition, waves and tidal water movements scour some areas exposing the solid limestone structure of the reef, which can provide a firm foundation on which corals can settle and grow.
Preliminary recommendation towards the coral reef recovery is to create an integrated coastal zone management where there should be greater regional cooperation to regulate overfishing, destructive fishing and commercial fishing on coral reefs, especially those of subsistence importance. Areas without coral reef protected areas or those with only a few should designate appropriate areas for conservation. Capacity Building would be the next recommendation, where personnel should be trained on coastal resources management, reef assessment/monitoring, environmental assessment, education, and enforcement. Partnership should be improved between traditional authorities and modern government agencies/ministries to establish monitoring networks and information sharing for promotional regional cooperate assistance. The information sharing will also greatly benefit the participating stakeholders in terms of improving scientific understanding of coral reef ecosystems.
Recovery from a natural disaster is variable. Often, branching corals recover quickly because of their rapid growth, and broken branches can even begin to regrow in new areas. However, recovery can be hindered by the accumulation and movement of coral rubble generated by the hurricane. Terrestrial runoff resulting from heavy rainfall can also influence the nearshore reef ecosystems, smothering corals with sediment and other debris, as well as increasing nutrients (including those in fertilizers) that influence growth rates of algae, lowering salinity, which can stress corals. The influence of hurricanes on coral reefs can be beneficial and detrimental. Small hurricane can provide fast relief during periods of thermal stress, whereas waves from large hurricanes can reduce a reef to rubble. Coral reefs have experienced these effects of hurricanes and survived millions of years; however, in light of the rapidly changing climate, the ability of corals to recover from severe storms, while facing the combined effects of increasing thermal stress and ocean acidification, could be extinguished.
Reference:
- httpss://underwater.com.au/article/id/10364-cyclone-yasi-and-the-great-barrier-reef/
- https://www.icriforum.org/sites/default/files/Pacific-Coral-Reefs-2011.pdf
- https://coral.org/home/839640.cloudwaysapps.com/qahwaptpdq/public_html/wp-content/uploads/2014/02/climatechange.pdf
- httpss://en.wikipedia.org/wiki/Cyclone_Winston
