Fuzzy Logic Method for Evaluating Habitat Suitability in an Estuary Affected by Land Reclamation

Abstract

This paper proposes an integrated approach to the assessment of estuarine habitat suitability based on a fuzzy logic method. Specifically, fuzzy logic is used to construct the Habitat Suitability Index (HSI) as a supplementary metric when field data is scarce. The HSI is used in turn to build the Habitat Aggregation Index (HAI) that considers the internal patches and fragmentation of the habitat. We applied the proposed tool to the Yellow River Estuary to demonstrate its implementation and efficacy. The habitat suitability of the estuary was evaluated under a host of scenarios with different terrain conditions to simulate the consequences of the long term land reclamation activities it has experienced during the past two decades. The findings indicate that from 1989 to 1999, the suitable habitat area (HSI ≥ 0.6) for jellyfish decreased by 2–6 % when flow was less than 500 m3/s, but increased 5–6.5 % when flow was greater than 800 m3/s. The suitable habitat area decreased by more than 30 % under the land reclamation that occurred from 1999 to 2009. The suitable habitat area for Chinese shrimp decreased by 9–13 % from 1989 to 1999 and 67–78 % from 1999 to 2009. Both the HAI of the habitat for jellyfish and Chinese shrimp decreased during 1989 to 1999 and then increased in 2009, indicating that the degree of habitat fragmentation that worsened under the reclamation during 1989–1999 was ameliorated during 1999–2009. This proposed approach provides a novel evaluation tool for habitat suitability in estuaries.