CC BY
13
https ://doi.org/10.29013/ELBLS -21-4-44-49
Tianrui Tan
The Experimental High School Attached to Beijing Normal University 14 Erlong Road, Xicheng District, Beijing, China E-mail: [email protected]
IMPACT OF HUMAN ACTIVITIES ON CORAL COVERAGE IN SANYA, CHINA
Abstract. The health condition of coral reefs has degraded seriously worldwide. Various factors account for the current decline of coverage of hard corals, including climate change, water pollution, spread of coral diseases, and an increase of natural predators. The development of tropical coastal regions has led to an increase in human activities, particularly in regions where coral reefs are present. Tourism, fishery, and aquaculture are potential human activities that can affect coral reef health. However, the impacts of such factors are still yet to be fully studied. To address this knowledge gap, this study developed a multiple linear regression model to quantify the impact of human activities, i.e., tourism, wild-capture fishery, and aquaculture, on coral coverage in Sanya, China. Annual overnight tourist number, wild-capture fishery production, and aquaculture production data in Sanya, China (2005~2018) were collected from official databases and reports. The results indicated a high correlation, R2 of 0.832, and revealing that the number of tourist and fishery production have a negative and significant impact on the coverage rate of live hard corals, while the impact of aquaculture production is not significant. These results identify the serious threat of human activities on coral reef ecosystem in Sanya, and will raise public awareness of the impact of human activities on coral reef health, providing valuable insights for policy makers to the design of new coral reef protection strategies for the sustainability of the reef and marine ecosystem.
Keywords: Coral coverage, Human activities, Regression analysis, Indo-Pacific region, Sanya
Introduction 70-90% of the energy of the wind-generated waves
Coral reefs play a significant role in marine eco- is absorbed by coral reef (3). Moreover, coral reef
systems and human life, maintaining biodiversity and coral reefs are attracting tourists around the world for
energy throughput of tropical regions. Coral reefs, activities like scuba diving & snorkeling, supporting
provide food resources, shelter, and spawning sites tourism in tropical coastal areas (4). to an array of different marine organisms, account- However, the health condition of coral reefs has ing for almost 1/3 of the marine species in the world degraded seriously throughout the world. Various
(1). The prolific marine organism resource also pro- factors account for the current decline of live hard
vided food, especially protein, for human. 10% of the coral coverage, including climate change, water
world's wild-capture fishery production comes from pollution, spread of coral diseases, and increase of
coral reef regions (2). Plus, the calcium carbonate natural enemy population (4-7). In recent years, hu-
structure formed by hard corals strengthens and pro- man activities have become increasingly prominent
tects the shore line. During tropical storms, at least in tropical coastal areas with the development of
economy. Sanya, located on Hainan Island, a tropical island on the continental shelf of South China Sea, is a famous coastal tourist city in China. It is also on the north edge of the Indo-Pacific region — the hotspot of world's coral diversity — and have the most developed fringing reef in China (4, 8). Human activity in Indo-Pacific region is drastic and has affected the health of coral reef. Harvest of coral is the most direct way of harming the health of coral reef and has caused serious coral coverage decline in China in the 1980s (4). However, coral reserves have been established in some parts of the Indo-Pacific region, and destructive mass-harvest of coral for construction material rarely occurs currently (4). Pollutions caused by sewage dump also occurs in the Indo-Pacific region, but the seriousness of that problem can be reduced by the increasingly strict restriction of sewage discharge (4). Overfishing and tourist activities are becoming prominent in recent years (4). Although these two kinds of activities, except destructive fishing method like dynamite fishing, may not affect coral reef health through direct damage, changes of surrounding organisms and environment caused by fish catch or the disturbance of tourists cannot be ignored (5, 9).
Previous studies of coral reef degradation in San-ya and other parts of the Indo-Pacific region have focused on the major causes in different regions. Tito et al. (6) observed that global warming accounts for the decline of live coral cover rate in Bali, Indonesia. Increased water temperature caused coral bleaching in large scale. According to Guo et al. (7), water acidification caused death of corals in Great Barrier Reef, Australia by destructing the calcium carbonate skeleton of corals. It is also unignorable that the impact of natural enemies to live coral coverage can be drastic in a short period of time. Wu et al. (5) noticed that in Xisha Islands, China, the boost of population of crown-of-thorns starfish (Acanthaster spp.), a kind of native predator of coral polyps, has contributed to the dramatic drop of live coral coverage from 53.8% to 7.93% between 2007 and 2009. In mainland Asia,
the most heavily populated area in the world, human impact is the major cause of coral reef degradation. Shi et al. (4) recorded 23 kinds human activities under 7 categories in Sanya, China and evaluated their impact level to coral reef health.
However, the previous studies about coral reef lack focus on quantitative analysis of co-relations between human activities and coral reefs, especially for newly emerged but rapidly developing activities such as recreations. Linear regression has been used to analyze the correlation between environmental factors and coral coverage. In the few existing quantitative analysis of human impacts on coral reef, a study of the impacts of recreation on coral reefs in Akumal, Mexico conducted by Gil et al. (9) used linear analysis to show the coral and algae coverage change under the disturbance of tourists.
A study using linear regression to quantify how serious the impact of human activities on the coral community in Sanya is can be influential. Apart from adding quantitative analysis of co-relations between human impacts and coral coverage, this study can also help people understand the leading factor causing coral reef degradation in certain areas and support the design of new coral reef protection measurements.
Methodology
The data in this study was originally collected in coral reefs along the coast of Sanya, China. The source of the data is "Report of the Situation of Chinese Coral Reef 2019"(10) and the Bureau of Statistic of Sanya (11).
This study focused on three determinants (independent variables), comprising tourism, wild-capture fishery, and aquaculture that affect the coral reef health in Sanya, China. The time range of data collected is 2005~2018.
In the study, tourism development was calculated from annual overnight tourist number of the regions. Wild-capture fishery was measured by annual marine wild-capture fishery production (tons). Plus, aquaculture was indicated by annual marine aquaculture production (tons). Finally, the coverage rate of live
hard coral (the dependent variable) was selected as the indicator of coral reef health.
Before analyzation, the data of annual overnight tourist number, annual marine wild-capture fishery production, and annual marine aquaculture production were normalized. The formula of this process is:
•y* - •y* I •y*
normalized max
In order to show the correlation between coral coverage and the human activities mentioned above,
multiple linear regression models were developed. The formula is:
y = alx l + a2X2 a3X3 + e y accounts for the dependent variable: live hard coral coverage rate. x1 is annual overnight tourist number; x2 annual marine wild-capture fishery production; x3 annual marine aquaculture production. a is the estimated coefficient for each independent variable and e is the standard error.
Results and Discussions
Table 1. The Findings of Determinants of Live Hard Coral Coverage in Sanya, China
Variable Estimated coefficients Standard deviation t-statistics P-value
Constant 67.762 13.977 4.848 0.001
Tourist number (Overnight) -37.423 5.905 -6.337 0.000
Wild-capture fishery production -30.268 12.900 -2.346 0.041
Aquaculture production 6.667 7.983 0.835 0.423
Multiple R=0.912 R2=0.832 Adjusted R2=0.781
The three factors analyzed account for about 83% of the decline in hard coral coverage (R2 = 0.832) (Table 1). The number of tourists and fishery production are both significant (P < 0.05) while aquaculture production is not (p = 0.42). Hence, it is reasonable to conclude that tourism and wild-capture fishery are serious factors affecting the health of coral reef in Sanya.
Table 1 shows that tourist number are negatively correlated with the coverage of live hard coral in Sanya with the estimated coefficient of-37.423. The result shown above indicates that the influx of tourists every year impose significant pressure on the health of coral reef in Sanya.
Currently, tourism in Sanya negatively affects the health of coral reef in several direct or indirect ways. Firstly, scuba divers and snorkelers can cause direct physical harm to live corals. Although deliberately touching or breaking corals are banned, accidental contact with corals underwater can be frequently observed among divers or snorkelers and cause physical damage to live corals (12). For example, under strong underwater currents, it is easy for divers to grab or even bump into corals, which can damage
soft tissues of polyps or ever crack calcium carbonate skeleton of corals (12). Plus, flippers of tourists can stir up seafloor sediments, which increase water turbidity and thus inhibit the growth of corals (12). Secondly, tourism can negatively influence the health of coral reef indirectly through pollution and the construction of tourism-related infrastructures. Hotels and restaurant built for tourists produce sewage and increase nutrient salt concentration of sea water, which cause eutrophication and inhibit coral growth (4, 13). Constructions related to tourism in coastal cities like Sanya often involve sea reclamation, which is disastrous to coral communities in shallow water along the coastline (4, 13)
In response to the problems caused by tourism, several actions should be considered. In order to relieve the pressure created by divers and involvers of other water sports, the number of tourist entry can be restricted. Diving spots like Wuzhizhou island in Sanya have already adopted a policy called diving-spot-rotation: opening different zones to tourists in different times of a year (12). Plus, setting higher sewage treatment standard ought to be considered when devising plans of coral reef preservation. Also,
the government should strictly control or ban sea reclamations in areas where coral reefs are present.
The next factor — wild-capture fishery production — is found to have negative correlation with coral coverage with the estimated coefficient of -30.268. This result indicates that fishery can also negatively affect the health of coral reef in Sanya.
According to previous studies, direct impact of fishery to coral reefhealth can be destructive. Practices like bomb fishing and electricity fishing used to be prevailed fishing methods in Indo-Pacific region and can still be observed frequently in developing countries in recent years (13). These destructive fishing methods can totally destroy coral reef ecosystem by decomposing reef structure and killing all the organisms living in the surrounding areas (14). After 1990s, destructive fishing method are banned by Chinese government and are greatly reduced in Sanya nowadays (5). In Sanya, fishery's most prominent impact on the health of coral reef is indirect. Although large-scale harvest of corals is rarely seen in Sanya after the national reserve of coral reef was established in the 1990s, overfish-ing of other marine organisms can be predicted to influence coral coverage. For example, Charonia tri-tonis, a kind of mollusk, is the major natural enemy of Acanthaster cf. solaris, which prey on coral polyps (15). A previous study has shown that overfishing of Charonia tritonis can cause the outbreak of Acanthaster spp., threatening live coral communities (15). Sanya's coral reef has experienced the rapid increase of Acanthaster spp. population from 2006 to 2008, during which the live coral coverage declined significantly from 47% to 38% (10).
In order to minimize the impact to the health of coral reef of wild-capture fishery, fishery regulations should be carefully devised. Apart from banning destructive fishing method, time period and places in which commercial fishery is allowed should be considered. China has already set fishing-prohibit season in summer and has received positive feedback (16). Fishing-prohibit zone in places where coral reef is present has been shown effective in reducing harms
of fishery to coral reef ecosystem in certain region like Wuzhizhou island, Sanya (12). Therefore, the policy of limiting or prohibiting the entry of commercial fishing vessels to certain coral reef zones can be added to the protection plan of coral reef in the scale of Sanya as a whole. Moreover, species which are important to the ecological equilibrium of coral reef ecosystem should be protected from overfishing. Catch share for species like large coral reef fish can be set to help the population of these species maintains stable.
According to the result listed in table 1, the correlation between aquaculture and live hard coral coverage is not significant. The estimated coefficient of this factor is only 6.667, and the P-value reaches 0.423 (exceeding 0.05), suggesting that aquaculture has a positive, but not significant, impact on coral reef health in Sanya.
Aquaculture can affect marine ecosystem both positively and negatively. Aquaculture can provide products to markets without catching individuals from the wild, which can relieve ecosystem's pressure created by overfishing (17). However, high-density aquaculture is able to cause pollution problems which are destructive to corals. The massive amount of feed, manure, and antibiotics released into water in aquaculture spots can cause eutrophication and inhibit coral growth (4, 18).In 2003, Shi et al. have recorded the decline of live coral coverage in places where aquaculture spots of algae and pearl shells were present in Luhuitou, Sanya (14).
In order to reduce the negative impact that aquaculture have on the health of coral reef and let aquaculture contribute to the protection of coral reef, scientific regulations are needed. The business conversion from fishery to aquaculture should be encouraged. But the density of individuals in an aquaculture spot should be limited. The use of antibiotics should be put under strict supervision. Sewage treatment technology need to be improved and the government ought to set up standard of sewage treatment.
Conclusion
This study identified the significant causes of coral reef degradation in Sanya, China by examining the correlation between human activities and live hard coral coverage with multiple linear regression. Human activities have a significant effect on the health of coral reefs in Sanya. Tourism and wild-capture fishery are major factors accounting for coral reef degradation in Sanya while the impact of aquaculture on coral reef health is slightly positive but not significant. When making policies of the protection of coral reef in Sanya, the scientific regulations of
human activities should be considered as important parts. Because studies about impacts of human activities to coral reef health began relatively late in China, valid statistical data of specific tourist activities, fishery practices, and aquaculture practices in Sanya are not accessible yet. In order to further understand the mechanism of how tourism, fishery, and aquaculture affect the health of coral reef, future efforts can be paid on the collection of frequencies of more specific activities like scuba diving and the analysis of their correlations with coral coverage.
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