Xuechu Chen

Traditional intensive agricultural system impedes ecological functions, such as nutrient cycling and biodiversity conservation, resulting in excessive nitrogen discharge, CH₄ emission, and ecosystem service losses. To enhance critical ecosystem services and mitigate environmental externalities in paddy fields, we developed a multi-objective agricultural system (MIA system), which combines two eco-functional units: paddy wetlands and Beitang (irrigation water collection pond). Pilot study results demonstrated that the MIA system enhanced biodiversity and inhibited pest outbreak, with only a marginal reduction in rice production compared with the control. Additionally, the paddy wetland effectively removed nitrogen, with removal rates of total nitrogen and dissolved inorganic nitrogen ranging from 0.06 to 0.65 g N m⁻² d⁻¹ and from 0.02 to 0.22 g N m⁻² d⁻¹, respectively. Continuous water flow in the paddy wetland reduced the CH₄ emission by 84.4% compared with the static water conditions. Furthermore, a simulation experiment indicated that tide flow was more effective in mitigating CH₄ emission, with a 68.3% reduction compared with the drying–wetting cycle treatment. The emergy evaluation demonstrated that the MIA system outperformed the ordinary paddy field when considering both critical ecosystem services and environmental externalities. The MIA system exhibited higher emergy self-sufficiency ratio, emergy yield ratio, and emergy sustainable index, along with a lower environmental load ratio. Additionally, the system required minimal transformation, thus a modest investment. By presenting the case of the MIA system, we provide a theoretical foundation for comprehensive management and assessment of agricultural ecosystems, highlighting its significant potential for widespread application.

Intensive farming in urban suburbs often causes habitat loss, soil erosion, wastewater discharge, and agricultural productivity decline, threatening long-term benefits for the local community. We developed a nature-based solution for sustainable land restoration by establishing “Green Treasure Island” (GTI). The aim of this study is to evaluate the ecological restoration effectiveness of GTI and explore its feasibility and replicability for future applications. The core eco-functional zone of GTI—a 7 hm² forested wetland—embedded a closed-loop framework that integrates land consolidation, ecological restoration, and sustainable land utilization. The forested wetland efficiently removed 65% and 74% of dissolved inorganic nitrogen and phosphorus from agricultural runoff, raised flood control capacity by 22%, and attracted 48 bird species. Additionally, this biophilic recreational space attracted over 3400 visitors in 2022, created green jobs, and promoted local green agricultural product sales. Through adaptive management and nature education activities, GTI evolved into a landmark that represents local natural–social characteristics and serves as a publicly accessible natural park for both rural and urban residents. This study demonstrates the feasibility of creating GTI for improving ecosystem services, providing a practical, low-cost template that governments and local managers can replicate in metropolitan rural areas worldwide to meet both ecological and development goals.

To improve the quality of natural seawater to meet the needs of aquaculture production, a large-scale subsurface-flow constructed wetland (HSFCW) was constructed and operated stably for 2 years to understand the reasons for its purification effect on natural seawater. The results of the study showed that the system could maintain a high purification effect on natural seawater during aquaculture; the average removal rates of COD, TSS, TN, NH₄⁺-N, and DON (organic nitrogen) were 22.29%, 49.33%, 36.94%, 10.88%, and 44.08%, respectively. Additionally, the HSFCW could effectively remove harmful algae such as Cyanobacteria; the removal rate of dominant algae species in Cyanobacteria was 90.33–97.93%. The pyrosequencing of 16S ribosomal DNA revealed that Proteobacteria, Nitrospirae, and Chloroflexi were the main and key bacterial phyla in the system. Members of these key gates are regarded as playing important roles in resisting water purification. The study results suggest that the subsurface-flow wetland system can effectively improve seawater quality and reduce the density of harmful algae cells.

Coastal wetlands, the major component of coastal ecotones with indispensable ecosystem services, are threatened by anthropogenic disturbance, resulting in continuous loss of ecosystem functions. Coastal wetland restoration can be implemented to deter the ecosystem losses; however, it is unclear whether it could provide appropriate habitat for the birds using on coastal ecotones. Here, we utilize a newly restored wetland as an example to investigate the impacts of coastal restoration on bird diversity, and test the hypothesis - if a reasonable habitat pattern is created, more birds will be attracted, thereby helping decision-makers develop efficient and sustainable coastal restoration strategies. We used Fragstats for landscape pattern analysis, and derived the variability in different habitat patterns by independent sample T-test and Mann-Whitney U test. The results suggested that the restored wetland exhibited a positive effect on attracting birds, with a total of 70 species, 35 families, and 15 orders of birds being recorded over a three-year period after restoration. Passeriformes are the main species, and accounted for 52.8% of bird species. Additionally, waterbird species, i.e., Ciconiiformes and Anseriformes, accounted for 24.67% of the total number of species. The number of bird species in the wetlands increased annually, especially during the overwintering and the breeding period. Furthermore, the results of this study indicate that water-centered mosaic-type habitat consisting of a relatively low degree of separation and high patch connectivity was beneficial to attracting different types of birds. The number of bird species, density, bird biodiversity index, evenness index, and dominance index for mosaic-type habitats were all higher than those for even habitat pattern with independent patches and sharp boundaries. In particular, the mosaic-type habitat attracted migratory waterbirds such as Anas zonorhyncha, Aix galericulata, Mareca penelope, Hydrophasianus chirurgus, Emberiza pallasi, Xenus cinereus, and Spatula querquedula, which expanded the range of birds attracted by coastal restoration projects. This study illustrated that coastal wetland restoration combined with a creation of water-centered mosaic-type habitat attracted more birds and could provide a reference for the restoration of degraded ecosystems in coastal zones.

In order to improve the quality of natural seawater to meet the needs of aquaculture production, a large-scale subsurface flow constructed wetland was constructed and operated stably for 2 years to study its purification effect on natural seawater. Studies had shown that the system could maintain high purification effect on natural seawater during aquaculture, and could effectively remove harmful algae such as Cyanobacteria, especially in warm months. The pyrosequencing of 16S ribosomal DNA revealed that Proteobacteria, Nitrospirae, chloroflexi were the main and key bacterial phyla in the system. Members of these key gates were regarded as the important roles in resisting water purification. In summary, the subsurface flow wetland system was suitable for large-scale seawater aquaculture plants, which could effectively improve seawater quality conditions and reduced the density of harmful algae cells.