Toward low-carbon management of Spartina alterniflora ecological restoration project in China: A multi-objective spatial optimization balancing carbon footprint and economic cost.

Spartina alterniflora is a highly invasive plant species in China's coastal wetlands, posing severe threats to ecosystem functioning and biodiversity while generating substantial environmental and economic burdens during large-scale control efforts. However, the carbon footprint and cost trade-offs of alternative restoration projects remain poorly understood at the national scale, limiting the design of sustainable management strategies. Moreover, no spatially explicit decision-support framework currently exists to jointly optimize restoration methods and biomass treatment pathways under heterogeneous regional contexts. Here, we integrate life cycle assessment with multi-objective spatial optimization to evaluate the carbon footprint and engineering cost of four widely applied S. alterniflora restoration methods, including mowing-plowing, mowing-shading, mowing-flooding, and mowing-plowing-planting, in combination with four straw treatment methods. Carbon emissions and costs were quantified per hectare and spatially optimized. Results show that mowing-plowing exhibits the lowest carbon footprint (4.64 t CO2-eq ha-1), whereas mowing-flooding produces the highest emissions (9.82 t CO2-eq ha-1) due to intensive electricity consumption. Straw management substantially reshapes project-level emissions, with biogas production providing net carbon offsets and landfill disposal causing high emissions (100.73 t CO2-eq ha-1). Spatial optimization identifies province-specific restoration portfolios that balance national carbon emissions (0.41 Mt CO2-eq) and economic cost (3.68 × 109 CNY), with mowing-flooding dominating in Shanghai and Jiangsu and mowing-plowing prevailing in most other provinces. This study provides a spatially explicit decision-support framework for low-carbon and cost-effective coastal restoration, offering advances in spatial planning for sustainable invasive species management under China's dual-carbon goals.