Effects of mangrove removal on benthic organisms in the Siangshan Wetland in Hsinchu, Taiwan

Abstract

Mangrove degradation is a well-documented trend, but the spread of mangroves within the Siangshan Wetland in Hsinchu, Taiwan, runs contrary to that trend. The spread of mangroves changes the structure and functions of habitats for benthic organisms, causes infilling of estuaries and flooding and creates breeding grounds for small black mosquitoes. A large-scale mangrove-removal project was undertaken by the Hsinchu City Government from October 2015 to March 2016. They also investigated the consequences of mangrove removal on benthic organisms and adjacent habitats from October 2015 to September 2016, and the density, species count, Shannon–Wiener index (H′), and Pielou’s evenness index (J′) of the mangrove and non-mangrove regions were compared. In this study, we used satellite telemetry images to monitor fluctuations in mangrove density from 2006 to 2016. The non-mangrove region exhibited more variations than the mangrove region. After mangrove removal, species returned to their original habitats and noteworthy biological values significantly increased in the mangrove regions. This study presents evidence to argue that mangrove removal benefits benthic organisms. The results indicate that mangrove removal can be an appropriate habitat rehabilitation strategy for benthic organisms. The ecological findings of this study can inform coastal managers or other officials who seek to steward mangrove biomass.

Sustainable Management of Coastal Wetlands in Taiwan: A Review for Invasion, Conservation, and Removal of Mangroves

“…This case presents Siangshan Wetland and includes a detailed report by Chen et al (2018) [12]. Siangshan Wetland is an important muddy wetland with abundant species and biodiversity in Taiwan.…”

“…Conservation and restoration operations have been undertaken by the mangrove management project to avoid the destruction and degradation of mangrove habitats [36]. Nevertheless, mangrove removal for these purposes clearly differs from the purpose of mangrove removal in the study by Chen et al (2018) [12].…”

“…Mangroves (Kandelia candel) have been planted since 1969, thus causing a change in the original habitat and posing a serious threat to the endemic Taiwanese fiddler crab species (such as Uca formosensis). The invading mangroves changed the structure and functions of the habitat for benthic organisms, caused sediment to accumulate with estuary flooding in heavy rain, and allowed invasions of the small black mosquito (Forcipomyia taiwana) [12]. Therefore, the Hsinchu City Government have launched several small-scale mangrove removal projects since 2000 and the mangrove area covered approximately 107 hectares.…”

“…Mangroves are beneficial for the following purposes: aquaculture, agriculture, source of firewood and building material, medicines, and for other local subsistence uses [11]. In the natural environment, mangroves serve as important breeding and nursery habitats for juvenile fish species, crab, shrimp, and mollusk species [12]. In general, mangrove areas have been identified to have high diversity and good ecological value [13] because they provide food and shelter, thus resulting in rich ecosystems [14,15].…”

“…The total of 37 relatively complete mangrove colonies has an area of approximately 1286 hectares (Figure 1). There are some kinds of ecosystem services provided by mangroves in Taiwan, including breeding and nursery habitats, food and shelter, aquaculture and fishery, pollutants trapping, coastal protection, and tourism [12,27,28]. Therefore, mangroves have become one of the main habitat types of coastal wetlands in Taiwan.…”