Method for modelling ecological competition based on Pareto optimality: A case study of coastal wetlands in Jiangsu Province, China

Abstract Competition is an important factor in determining the evolution of ecosystem population (or community) structure and the change in system functions, which are usually manifested directly at the system structure level. From the perspective of ecosystem services, based on the Pareto optimisation theory, we selected the coastal area of Jiangsu, China as the study area and carried out a study of equivalent competition among ecosystem populations (or communities). Firstly, we divided the study area into the region with nature reserve (NRR) and the region without nature reserve (Non-NRR). The study was performed through clarifying the ‘structure–process–function–service’ cascade relationship of the ecosystem and quantifying the value of major ecosystem services. Then, based on the theory of competition/coexistence, considered the population (or community) in the regional complex ecosystem as the object, we used the reference point-based non-dominated sorting (NSGA-III) algorithm to simultaneously optimise each ecosystem service to obtain a compromised Pareto optimal solution set. Finally, the technique for order preference by similarity to an ideal solution (TOPSIS) was used as a comprehensive evaluation method based on the criteria importance through inter-criteria correlation (CRITIC) weighting method for multi-objective decision-making to obtain the optimal balance of regional ecosystem services. The optimal balance implies that various groups can not only ensure that their own service values are maximised but also interact with other groups to maintain a state of synergistic competition and common development. The results showed that the characteristics of ecological services values under the optimal balance state of the coastal areas in Jiangsu are compatible with the regional ecological conditions; the dominant service types (and their proportion of the total value in NRR and Non-NRR) are carbon fixation (50.70 and 50.23%), climate regulation (13.29 and 12.34%), food production (8.40 and 10.90%), water supply (8.83 and 6.60%), gas regulation (7.72 and 8.73%), and flood storage (4.95 and 5.24%). Compared to the current average service value, this status has increased by 38.61% and 23.60% respectively, in NRR and Non-NRR. The corresponding optimal population (or community) structure (and the area ratio of each population in the two regions) is dominated by forest land (40.62 and 28.74%), paddy fields (24.16 and 37.44%) and meadows (9.42 and 10.70%), and the coastal wetland populations primarily including reeds (9.78 and 3.59%), aquaculture water bodies (7.46 and 3.86%) and Spartina (3.32 and 5.60%). The structural characteristics are consistent with the development law of ecological competition and succession of the coastal wetland system in this region and the direction of ecological service value optimization. The ideas and methods proposed in this study can provide a new direction for ecological competition research.