Nature-based Solutions (NbS) are actions to protect, conserve, restore, sustainably use and manage natural or modified ecosystems that address societal challenges while simultaneously providing human-well-being, biodiversity and resilience benefits. This wording was formally adopted by the UN Environment Assembly (UNEA-5) and echoes the earlier definition promoted by IUCN. 
Within an ESG context, the topic covers any corporate programme that leverages ecosystems to deliver outcomes such as climate-mitigation (carbon sequestration), climate-adaptation (flood or heat-risk reduction), water-security, soil-health improvement or biodiversity-net-gain. It spans on-site interventions (e.g., wetland restoration around a facility) and off-site initiatives financed through supply-chain projects or high-integrity carbon/biodiversity credits.