This report assesses the benefits and opportunities provided by Green Infrastructure (GI) in the GreenArc area in Hertfordshire. The landscape of Hertfordshire is characterised by a variety of landscape types, some of which are relatively rare. Hertfordshire has a rich GI resource encompassing parts of the Chilterns Area of Outstanding Natural Beauty (AONB), river valleys, chalk grasslands, farmlands, ancient woodlands, designated landscape and parklands, in addition to an extensive 20th century urban green infrastructure heritage. The supply and demand for GI was analysed, and maps were produced using Geographic Information System (GIS) map layers to understand spatial information. 11 functions of GI were mapped, and the need, supply and opportunity for each function were assessed. Whilst these functions are not referred to directly as ‘ecosystem services’ they reflect the services that the natural environment provides to human societies. These functions are: access to recreation, prestige on settlement approach corridors, health, sound ecosystems, productive green environments, historic landscape character, sustainability and responding to climate change, land remediation, nature conservation, experience of special landscapes, and flood attenuation and water management.