海平面上升影响下广西钦州湾红树林脆弱性评价

Abstract

Sea level rise caused by global climate change has significant impacts on coastal zone. The mangrove ecosystems occur at the intertidal zone in tropical and subtropical coasts and are particularly sensitive to sea level rise. To study the responses of mangrove ecosystems to sea level rise,assess the impacts of sea level rise on mangrove ecosystem and formulate the feasible and practical mitigation strategies are the important prerequisites for securing the coastal ecosystems. In this research,taking the mangrove ecosystems in the coastal zone of Qinzhou Bay,Guangxi province as a case study,the main impacts of sea level rise on the mangrove ecosystems were analyzed by adopting the SPRC( Source- Pathway-ReceptorConsequence) model. An indicator system for vulnerability assessment on coastal mangrove ecosystems under sea level rise was worked out,according to the IPCC definition of vulnerability,i.e. the aspects of exposure,sensitivity and adaptation.The rate of sea level rise,subsidence /uplift rate,habitat elevation,daily mean inundation duration,intertidal slope and sedimentation rate were selected as the key indicators,taking into account of the characteristics of quantification,data accessibility,spatial and temporal heterogeneity. A quantitatively spatial assessment method based on the GIS platform wasestablished by quantifying each indicator,calculating the vulnerability index and grading the vulnerability. The vulnerability assessment based on the sea-level rise rates of the present trend( the rate of sea level rise in the past 40 years),the B1 and A1FI scenarios in IPCC SRES were performed for three sets of projections of short-term( 2030s),mid-term( 2050s) and long-term( 2100s). The results showed the mangrove ecosystems in the coastal zone of Qinzhou Bay was within the grade of no vulnerability at the present sea level rise rate of 0.29 cm /a and the B1 scenario of 0.38 cm /a for the projections of2030s,2050s and 2100s,respectively. As the sedimentation and land uplift could offset the rate of sea level rise and the impact of sea level rise on habitats /species of mangrove ecosystems was negligible. While in the A1FI scenario at sea level rise rate of 0.59 cm /a,the percentage of mangrove ecosystems within the grade of low vulnerability could reach 41.3% in2050,and increased to 69.8% in 2100. The spatiotemporal occurrences of low vulnerability were mainly distributed in the northern coast of Maoweihai. The SPRC model and the methodology for vulnerability assessment developed from this study can objectively and quantitatively assess the vulnerability of coastal mangrove ecosystems in Qinzhou Bay under the impact of sea level rise caused by climate change. Based on the results from this study,some mitigation measures should be considered in the future for securing the coastal mangrove ecosystems,which include management of sedimentation,rehabilitating and recreating mangrove habitat,and controlling reclamation. The results from this study could provide a scientific basis on formulating feasible and practical mitigation strategies for coastal mangrove ecosystems under the impact of sea level rise,which is an important prerequisite for securing the coastal zone ecosystems.