NEC Contracts has updated Option X29 to formally recognise nature alongside climate change in infrastructure and built environment delivery, marking a significant milestone in the evolution of environmental considerations within NEC contracts. The update was announced at the NEC Annual Conference on 18 June 2026.
From carbon to nature and climate
Option X29 was originally developed to give contracting parties a standard mechanism for setting, measuring and incentivising environmental performance across the project lifecycle. In its original form, the clause focused on climate change mitigation, embedding whole-life carbon requirements, including embodied carbon reduction targets and operational performance, into NEC contracts. This addressed a recognised gap in procurement: the absence of a contractual lever capable of driving measurable carbon outcomes alongside commercial performance.
The revised Option X29 now introduces a Nature and Climate Hierarchy to support implementation. At its core is a principle of working with nature first, encouraging projects to consider nature-based solutions, nature-positive infrastructure and blended green-grey approaches before progressing to traditional engineered solutions where necessary.
The guidance also includes worked examples and practical performance measures covering:
- Biodiversity net gain
- Habitat connectivity
- Drought resilience
- Sustainable urban drainage systems
- Canopy cover
- Soil health
- Carbon sequestration
Where the idea began
The initiative to expand Option X29 beyond climate began during the ICE presidential year of Prof Anusha Shah, whose theme, "Making Connections for a Nature and People Positive World," highlighted the relationship between infrastructure, people and the natural environment.
Prof Shah subsequently approached Rekha Thawrani, Global Director of NEC Contracts, and Peter Higgins, Chair of the NEC4 Contract Board, to explore how the clause could evolve to embed nature. Peter mobilised an NEC Working Group led by Ian Heaphy of the NEC4 Contract Board, bringing together specialists from Plan for Earth, Arcadis, WSP, AECOM and the Environment Agency, alongside ICE representation, to take the work forward. The amended guidance and Practice Note were subsequently developed by Prof Anusha Shah and Dr Martina Girvan with the input and support of the NEC Working Group.
One mechanism, two outcomes
The integration of nature into X29 complements and reinforces, rather than replaces, the climate function of the clause. Nature-based and nature-positive solutions can deliver multiple outcomes through a single intervention, including measurable carbon reduction, climate resilience, biodiversity enhancement and improved health and wellbeing.
Improved soil health, increased canopy cover and peatland restoration, for example, all contribute to carbon sequestration and storage while also providing flood attenuation and thermal regulation. Prioritising these approaches over conventional engineered solutions further reduces embodied carbon by decreasing material demand.
X29 therefore provides a single contractual mechanism capable of driving progress on both climate and nature, aligned with the UK's Net Zero commitments and the growing need across the infrastructure sector for whole-life environmental performance.
What NEC Contracts and ICE leaders are saying
Rekha Thawrani OBE, Global Director of NEC Contracts, said:
The expansion of Option X29 reflects where the industry needs to go. Climate and nature are not separate challenges, they are deeply connected, and our contracts need to reflect that. By providing a single mechanism that drives performance on both, we are giving contracting parties a practical tool to deliver measurable environmental outcomes alongside commercial success. This is NEC doing what it has always done: evolving to meet the needs of the sector.
Prof Anusha Shah, ICE President 2023-2024, said:
Infrastructure shapes the natural world as much as it serves it. This update to Option X29 is a direct result of the conversations and connections made during my presidential year, and I am proud to see that vision become a reality. Embedding nature alongside climate within procurement and contract frameworks is not just good practice, it is essential if we are to move beyond simply reducing harm to nature and move towards infrastructure that restores nature, builds resilience and creates long-term environmental, social and economic value.
Download the updated Option X29 Nature and Climate Clause
Download the updated Option X29 Nature and Climate Practice Note
The Institution of Civil Engineers (ICE) acknowledges the help in updating the secondary Option X29 given by the NEC4 Contract Board and the following:
- Prof Anusha Shah (ICE President 2024-2025), Founder & CEO, Plan for Earth Ltd
- Dr Martina Givan (Nature lead for Arcadis and Chair of the Biodiversity and Environmental Net Gain group for the Green Construction Board)
- Prof Lewis Barlow (WSP Decarbonisation Head of Profession and ICE Trustee for Carbon and Climate)
- Chris Landsburgh (Carbon, Environment and Sustainability Director at AECOM)
- Siu Fa Ng, Project Executive, Environment Agency
- Veronica Flint Williams, Contract and Risk Manager, Environment Agency
- Brandon Murray (Technical Director at Arcadis)
- Visual Communication: Mags Ashmore, Visual Literacy Lead at Arcadis
The NEC4 Contract Board is:
- Peter Higgins, BSc (Hons), CEng, FICE (Chair)
- Ian Heaphy, BSc (Hons), FRICS, FCIArb, FCInstCES, MACostE
- Matthew Garratt, BSc (Hons), MRICS, FCIArb
- Shy Jackson, LLB, LLM, MSc, FCIArb, FCInstCES
- Dale Evans, BSc, FICE, CEng, MBA
- Professor David Mosey, CBE, LLB (Hons), PHD
- Helen Sturdy, CEng, MSc, BEng (Hons), FIHEEM, CIWFM, MCIBSE, MAPM, MAfH
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