Geography Desertification of Coral Reefs

Geography

Desertification of Coral Reefs

Coral reefs are under threat worldwide. An estimated 58% of reefs are classified as threatened and 11% of the original amount of coral reefs has already been lost. The makeup of remaining coral reefs is also rapidly changing. In regards to many of the reefs, the decline in coral has coincided with increased cover of macro algae, which has caused apparently stable community shifts to algal-dominated states. The reasons for the coral decline are thought to include a combination of direct anthropogenic factors, such as overfishing, pollution, and sedimentation as well as climate change and natural disturbances (Gardner, Cote, Gill, Grant and Watkinson, 2005).

The overall goal of coral reef management is to maintain the ability of tropical reefs to provide the ecosystem goods and services like fisheries, tourism, aesthetic and cultural values. Although there have been some successes, current management of reefs has failed to achieve this goal. In many locations around the world, manmade stresses to coral reefs have exceeded their regenerative ability, causing dramatic shifts in that make up of species and has resulted in several economic losses (Bellwood, Hughes, Folke and Nystrom, 2004).

Coral reefs are three dimensional shallow water structures that are dominated by sleractinian corals. In the absence of severe human impacts, reefs readily reassemble after routine disturbances such as tropical hurricanes. Many modern coral reefs are increasingly failing to regenerate after natural and human impacts, and have undergone a rapid shift to an alternate state. The most familiar of these traditions is from dominance by corals to dominance by fleshy seaweed, although several other transitions have been seen. The extent to which alternate states are stable or reversible is poorly understood and represents a major challenge for research and management of reefs (Bellwood, Hughes, Folke and Nystrom, 2004).

The purpose of this paper is to look at what areas of the world are affected by the desertification of coral reefs and what environmental impacts are being seen. The issues will be identified and then the solutions will be discussed. This will included a look at what efforts, if any, are currently being made to address the problem and what obstacles or barriers exist to solving the problem. What needs to happen in the future to address the problem more effectively and who needs to do what will also be looked at.

State of the Issue

As varied as its inhabitants and geography, the coral reefs of the U.S.A. show almost all the variability of which these systems are capable of. Coral reefs occur in U.S. territories on one of the most stable passive margin. It is one where no plate subduction or collision occurs, which keeps tectonic deformation relatively slight which. In Florida, this has created one of the largest and thickest carbonate platforms found in the ocean today. That platform shows all changes from a rimmed platform where a reef at the edge encloses a carbonate platform with very gentle bathymetry, to an unrimmed platform where the carbonate platform is unprotected by shelf-edge reefs, to a homoclinous ramp where the seafloor slopes uniformly towards the deep. This is unlike in the platforms, which have an abrupt change in topography at the shelf-edge, to a distally steepened ramp where the uniform slope is distally accentuated, and shows many of the responses coral reefs are capable of producing in response to shelf morphology (Riegl and Dodge, ().

Hawaii is located in the middle of the North Pacific Ocean. Hawaii's coral reef communities provide food and recreation to the people of Hawaii and are critically important to the State's approximately $800 million/year marine tourism industry. More than 70% of the state's people live on Oahu, and are mostly in Honolulu. Besides the resident population, nearly seven million tourists visit Hawaii each year. This ever increasing population has put anthropogenic pressure on Hawaii's coral reefs through various direct and indirect means (Jokiel, ).

The major natural factors that influence reef coral community structure and reef fish community structure in the Hawaiian Islands include currents, waves, substrate type, depth, island age, and rugosity. Some of these important constraints show correlations with each other. Generally, Hawaii's coral reefs are in better condition than many other reefs around the world. Coral ecosystems in the MHI are in fair to excellent condition, but are threatened by continued population growth, over fishing, runoff, and development. There is clear support of overexploitation of many food fishes and invertebrates. Introduced aquatic alien species have had an impact on the structure and function of Hawaii's reefs and may actually over take endemic species. Human activity has already taken a toll on the reefs of the populated high islands. It has been shown that human population within 5 km of a reef has had a negative relationship in Hawaii with coral cover, diversity and species richness. This suggests that anthropomorphic stressors are important contemporary forces shaping Hawaii coral reef community structure along with natural factors (Jokiel, ).

The Pacific Remote Islands Area (PRIA) is made up of a total eight islands and atolls,. These reefs form part of Line and the Phoenix Islands, and are associated with the Line and Tokelau Ridges of Cretaceous age. They consist of a basaltic core with limestone caps dated to variable age, some to the Cretaceous but not all are adequately cored. The atolls harbor a typical Indo-Pacific and rich coral reef fauna. All atolls are protected as National Wildlife Refuges and include some of the most pristine coral reef ecosystems in the United States (Maragos et al., )

Ocean acidification, in response to increasing levels of atmospheric carbon dioxide, has been projected to have widespread and chronic negative impacts on marine calcifiers. The calcifiers on PRIA reefs, including corals, crustose coralline algae, sand-producing Halimeda algae, and many shell producing invertebrates are likely to be affected by these global carbon chemistry changes in this area (Maragos et al., )

The morphologic variety of coral reefs, present and past, on the south, south-west and west Florida platform results from the interplay of antecedent topography, substrate type, sea-level fluctuations and water circulation. The broad nature of a ramp allows for extensive, lateral movement of the shoreline during sea-level cycles thus allowing for a diverse distribution of shorelines and shallow-water coral reefs. Where margins are steep, reefs become laterally compressed and vertically stacked. The rim-to-ramp transition along the south margin of the Florida platform adds to this complexity. The small circular reef banks seem anomalous as compared to expected reef linearity imposed by laterally extensive shelf margins and paleoshorelines. In the Florida Middle Ground area, perhaps karst pinnacles provided the original antecedent topography on which these numerous small reef banks became established. Additionally, all reefs seem to be dominated by aggradation, backstepping, or drowning rather than progradation suggesting that rapid sea-level changes have been critically important in their development. Sea-level fluctuations result not only in depth changes but also significant changes in shelf/adjacent deepwater circulation, water temperature, water quality as well as concomitant changes in continental/marine interaction. Healthy coral-reef development occurs when ideal conditions for substrate availability, water quality, and stable or slowly rising sea-level simultaneously converge. The diversity of reefs dispersed on the Florida platform indicates that such convergence is neither simultaneous nor everywhere (Hine et al., )

Hurricanes and tropical storms are possibly the most apparent and frequent natural disturbances that affect reef communities. They have long been recognized as being important determinants of both the structure and function of reef ecosystems. A number of studies have shown the severe immediate consequences of hurricane impacts at single sites in terms of reduced coral cover, highlighting the effects as being impressive in magnitude, speed, and patchiness. Hurricanes can also have minimal or barely visible impacts. Variability in immediate effects of hurricanes has been credited to either natural variability in reef structure, the presence of other overriding stresses and the scale of observation. The longer-term course and recovery patterns of coral populations following disturbances are not yet well understood (Gardner, Cote, Gill, Grant and Watkinson, 2005).

Solutions

One solution that has been used is that of seeking help from others who have more experience. New Caledonia has enlisted Australia's help in order to protect its massive coral reef. This is the world's second biggest reef after the Great Barrier Reef. This French Pacific territory has hoped to tap Australian research and expertise to maintain the reef, which rings its main island and is listed as a UNESCO world heritage site. Australia has a lot of experience in the management of the coral reef. New Caledonia would like to seize the opportunity of their experience and exchange scientific information on research projects with regard to those two reefs, which are the largest in the world and which are essentially facing each other across the sea (New Caledonia taps Australia for reef protection, 2010).

Numerous mitigation and restoration projects have been conducted in Hawaii. Reef restoration efforts using transplanted corals have failed along exposed coastlines due to destructive storm waves and other factors. Yet, there have been transplant successes in sheltered embayments. One of the major conclusions that have been seen is that the cost of reef repair and coral transplantation is generally high but effectiveness is usually very low. Protection and conservation, rather than restoration of damaged reefs, is the preferred priority. However, there have been a number of successful mitigation efforts in Hawaii (Jokiel, ).

Disorder is a natural structuring force in both terrestrial and aquatic communities, with disturbed patches undergoing cycles of removal and recovery leading to spatial heterogeneity. Whether uproar is acute or chronic has significant implications for the disturbed ecosystem's time frame for recovery, with lower chances for recovery after chronic, long-term disturbances or after a phase shift from one major community to another like from coral-dominated to algal-dominated reefs. Hard corals mainly Scleractinia form the biological and structural foundations of coral reef ecosystems, and can recover rapidly if communities are adapted to high disturbance regimes or if stable and complex substrate remains to facilitate recruitment. Nonetheless, blast fishing is an anthropogenic disturbance that physically alters the reef structure. The explosion of homemade bombs not only kills fish but also shatters the coral skeletons, and creates expanses of unstable coral rubble that reduces survival of coral recruits. In addition, the removal of the targeted herbivorous fish is likely to reduce the resilience of the reefs to climate change and other impacts, further hampering recovery. Blast fishing is widespread even though it is illegal, and a major threat to reefs with destructive fishing estimated to threaten over 50% of reefs in Southeast Asia. Coral remains that are not killed by the blast directly may experience further post-disturbance mortality in the shifting rubble (Fox and Caldwell, 2006).

Although recovery from blasting has been modeled and levels of biological or economic impact have been assessed, field studies of recovery from blast fishing are rare. It has been reported that there is a remote area in Indonesia where fishing with homemade bombs still occurs. In early April 1999 it was observed that two bomb fishermen using a kerosene-fertilizer mix in 300-mL glass soda bottles with homemade fuses were carrying out this practice. The fishermen gathered several kilograms of the targeted reef fish per blast. Hours after the blasts, the reef was surveyed using SCUBA. The approximate center of each of the resulting six craters was marked and measured the size of damaged areas. Researchers have returned to these sites repeatedly over the following five years to measure the dynamics of coral recovery (Fox and Caldwell, 2006).

It is progressively clearer that the rapid decline of reef systems calls for a suite of more vigorous, innovative and adaptive management strategies. Responding to the global coral reef crisis requires active management of human activities that modify essential ecological processes. In particular, it requires an ability to scale up management and governance of systems to secure the future of functional groups and their roles in supporting the resilience of coral reefs. There is an increasing awareness of what has already been lost, and also recognition that in a changing world, the resilience of coral reefs is increasingly uncertain (Bellwood, Hughes, Folke and Nystrom, 2004).