Key takeaways
Broader environmental focus
Option X29 now addresses nature and climate consideration within a single mechanism.
Integrated project management
Option X29 embeds nature and climate risks into planning, monitoring and early warnings.
Increased contractor risk exposure
Contractors should carefully review environmental obligations at tender stage where Option X29 is to be utilised.
In June 2026, NEC updated its Option X29 clause to ’formally recognise nature alongside climate change in infrastructure and built environment delivery’, as well as the corresponding practice note, now containing updated guidance as to how the revised clause should be applied and interpreted.
The update to this clause comes at a time when developers are under increasing pressure to demonstrate measurable environmental performance. Historically, in infrastructure and construction projects, nature-related matters, such as biodiversity enhancement, habitat creation and sustainable drainage, were generally driven by planning requirements and addressed through environmental assessments and design development.
The significance of the revised Option X29 is that it seeks to move those considerations beyond the planning and design stages into a clear contractual framework where environmental outcomes can be clearly allocated, monitored and incentivised.
What is Option X29?
The Option X29 clause is an optional secondary clause available across the NEC4 suite of contracts. For the purposes of this article, we have focussed on its operation within the NEC4 Engineering and Construction Contract (ECC).
When Option 29 was originally introduced as ’Option X29 Climate Change’ in 2022, it aligned with a growing emphasis on carbon reduction across the infrastructure sector, with contractors obliged to comply with any climate change requirements contained within the scope, amongst other things. At this point in time, major projects were already exploring innovative approaches to reduce carbon emissions, with HS2 commencing construction in 2020, one of the first UK construction projects to use fully electric giant crawler cranes as part of wider decarbonisation efforts.
Following the updates in June 2026, the scope of the revised Option X29 has been expanded to address nature and climate change impacts and considerations in one single mechanism. The requirements, plans, obligations and incentives in the original clause all reframed and renamed accordingly, thereby seeking to accommodate a broader range of environmental considerations, including biodiversity enhancement, habitat connectivity, soil health, sustainable drainage, drought resilience and carbon sequestration.
In brief terms, the now revised Option X29, if adopted (without amendment) provides that:
The Contractor will be obliged to comply with Nature and Climate Requirements, which are any requirements relating to nature and climate stated in the Scope, meaning that any failure to comply with these requirements may amount to a breach of contract and give rise to a Defect, making careful drafting and objective measurement important.
The Contractor will be required to prepare a Nature and Climate Plan setting out how it intends to achieve the Nature and Climate Requirements and collaborate with identified Nature and Climate Partners (i.e., people or organisations identified as those who will contribute towards the achievement of the requirements).
The Contractor will be obliged to issue an Early Warning Notice if it becomes aware of any matter which may adversely affect the achievement of the Nature and Climate Requirements.
The Contractor may also be required to achieve nature and climate related “performance targets” in Providing the Works detailed within a performance table in the Contract Data (the “Performance Table”), with these requirements separate and distinct from the Nature and Climate Requirements forming part of the Scope (albeit they may be similar). This Performance Table will also set out the adjustment to payment if the Contractor overperforms or underperforms in respect of any of these performance targets.
A notable feature of the updated practice note is the introduction of the ’Nature and Climate Hierarchy’, a design decision-making framework, which is highlighted as a potentially useful tool for developers and contractors when considering how nature and climate objectives should be delivered in practice on future infrastructure projects.
Commentary
The update to the NEC clause is reflective of the broader trend in infrastructure procurement towards the promotion of nature recovery and biodiversity, with many projects often required to deliver measurable benefits for the natural environment. This follows the recent developments in planning and environmental law, including the introduction of the mandatory 10% biodiversity net gain requirement for most new developments under the Environment Act 2021, requiring developments to leave wildlife habitats in a measurably better state than beforehand.
Although contractually obliging contractors to achieve planning and environmental requirements is far from a new concept, from a developer or employer perspective, the updated option clause should assist in providing a clearer framework for allocating, managing and incentivising these environmental requirements and outcomes, while also making it easier for contractors to understand (and achieve) their obligations and the consequences of them failing to comply with the same.
As the mechanism will likely result in a clearer allocation of risk, careful consideration of the proposed scope and the nature and climate requirements contained therein will be particularly important for contractors at tender stage, ensuring it is in a position to understand and price risk accordingly.
Our Construction and Engineering team advises on NEC contracts, procurement and project risk . Find out more on our Construction and Engineering page or contact us today to discuss how we can support you.
This article was co-authored by Paralegal, Becky Wright.
