Global climate change has emerged as a major threat to humanity and the Earth's ecosystems in the 21st century. While “carbon peaking” and “carbon neutrality” remain the core of global climate policy

a carbon-centric approach overlooks the fundamental role of the water cycle in climate regulation and regional resilience. This paper proposes and empirically tests the “Sponge Planet” concept—nature-based solutions(NbS) centered on restoring the Earth's water cycle—using land-use and water-driven strategies to achieve both climate mitigation and adaptation

while delivering ecological

disaster reduction

and socio-economic co-benefits. Four case studies in Hainan

i.e.

Sanya Dong'an Wetland

Haikou Meishe River

Sanya Mangrove Park

and Haikou Jiangdong “Breathing Seawall”

demonstrate the concept's applicability and effectiveness in tropical monsoon regions. Results show significant improvements in flood resilience

urban heat island effect mitigation

water quality

biodiversity restoration

as well as tourism

education

and urban quality enhancement. The paper recommends positioning water cycle restoration alongside carbon reduction as twin pillars of global climate governance

incorporating the “Sponge Planet” concept into the national 15th Five-Year Plan to lead a new paradigm in global climate adaptation and ecological civilization construction.