Revisiting the effectiveness of biodiversity offsets in coastal wetlands of China through landscape connectivity

Abstract

We modified the landscape connectivity calculation method and applied it to assess changes in temporal connectivity under different offsetting scenarios in the Yellow River Delta High-efficiency Ecological Economic Zone of China. We evaluated landscape connectivity based on resistance surfaces, least-cost distances, habitat areas, and the probability of dispersal between wetland patches in the landscape. The landscape connectivity declined between 1980 and 2015, with the degree of decline varying with the type of wetland. The cumulative percentages of freshwater marsh, salt marsh, and tidal marsh habitat areas that could be offset were 100 %, 100 %, and 34 %, respectively. However, the maximum landscape connectivity that was compensated for was only 1.2–10.4 %. When the offset patches were restored to freshwater marsh, the highest connectivity of coastal wetlands was achieved. There were substantial gaps between the area of habitat restoration offset required to achieve no net loss and the landscape connectivity that would ensure ecological effectiveness. The compensation area required to achieve no net loss of landscape connectivity was greater than that required to achieve no net loss of habitat area. We provide guidance for policy makers on how to implement offsetting to develop and manage green corridors, thus allowing movement that will ensure species’ survival. It was suggested that the passive restoration of isolated coastal wetland may be difficult to achieve. Policies that seek to increase landscape connectivity offsets can effectively promote population diffusion and migration, avoid habitat fragmentation, and are key to improving no net loss effectiveness.

Keywords

• Biodiversity offsets
• Landscape connectivity
• Sustainable development
• Coastal wetlands
• Ecological compensation
• Effectiveness