Following the publication of our book, Landscape as a Catalyst for Change (2025), Landezine asked me to reflect on two recent policy shifts in the UK that aim to strengthen the role of landscape in addressing environmental challenges: the Urban Greening Factor (UGF) and Biodiversity Net Gain (BNG). Central to these shifts is the Environment Act 2021, which establishes a statutory framework for improving air and water quality, managing waste, and reversing biodiversity decline. It introduces long-term environmental targets, strengthens monitoring and enforcement through the Office for Environmental Protection, and embeds ecological considerations more directly within the planning process. While UGF is adopted in London planning policy, BNG is a mandatory strategy in England’s planning system.

Reflecting on the last decade in practice has been bittersweet. Landscape architects are, I think, eternal optimists so it has been difficult at times to stomach the past decade – the self-flagellation of Brexit, the COVID pandemic, war in Europe and increasing geopolitical instability have coincided with the visible deterioration of natural systems and the accelerating impacts of climate change.

Recessions, austerity, and persistently low productivity in the UK have been compounded by crippling price rises and inflation following Russia’s invasion of Ukraine and more recent turmoil in the Middle East. These pressures have stalled brilliant projects, forced the closure of great practices, and bankrupted forward-thinking developers.

The once-in-a-century global pandemic was perhaps the least foreseeable event and marked a real shift in the way we think and the way we work. Lockdown made us stop and reflect, slow our pace of life, and, whilst searching the skies for vapor trails, opened our eyes to the beauty of nature, our ears to birdsong, and turned 3 million more Brits to their gardens.

During this period, even modest and temporary landscapes took on an expanded role. Spaces such as the temporary Meadow at Elephant & Castle, combining biodiverse planting, informal play, and social seating, became essential forms of everyday infrastructure, offering access to nature, space for movement, and a sense of place under conditions of restriction. For many residents, these were the only accessible open spaces within walking distance, foregrounding the importance of proximity, ecological quality, and usability. Such experiences reinforced a broader recognition: that landscape operates not only as a designed amenity, but as a critical component of urban resilience.

It will be a mark of the next decade how AI supports or complicates practice, and how metric-driven tools such as UGF and BNG are integrated more holistically. A key question remains how far value engineering can be balanced to allow landscape to retain a structuring role within projects.

What is the Urban Greening Factor?

The Urban Greening Factor (UGF) is a planning tool to evaluate the quality and quantity of urban greening and has been adopted within Local and London Plan Policies to ensure developments reach targeted minimum levels of greening. The goal of the UGF is to address urban challenges through “green infrastructure” rather than just traditional “grey infrastructure”.

UGF plays a role in improving city-wide green cover, reducing a wide range of climate change effects such as the Urban Heat Island effect, air pollution, and carbon levels, alongside creating habitats for wildlife and supporting Biodiversity Net Gain targets. It is also important for public health by improving air quality, dampening noise pollution, and providing residents with access to green spaces for mental and physical wellbeing.

In the project Cardinal Place, for example, we sought to undo some of the mistakes of the past. In the early 2000s, when Cardinal Place was originally developed, a familiar formula dominated public realm design across the UK: expanses of grey granite paving, a few oversized but poorly accommodated trees, and clipped single-species hedging. The result was often technically well detailed but environmentally sterile. The brief from the client, Landsec, emerged directly from users, tenants, and the surrounding community. The feedback was clear: transform the grey, hard landscape into something greener, more sociable, and more joyful.

Using UGF

The UGF calculation is normally carried out by the Landscape Architect – UGF sets out weightings (Factors) for each of the Surface Cover Typologies that may be included on a project. These are scored from 0 to 1 based on their habitat potential and their contribution to natural ecosystems.

As the design progresses, the anticipated area for each Surface Cover Type can be fed into the calculator to assess the UGF. Within the calculator, the area of each surface type is multiplied by its factor. The collated score is finally divided by the total site area (the full extent of the red line boundary) to calculate the overall UGF score.

On the whole, the minimum targeted score tends to be 0.3 for a commercial development and 0.4 for residential developments, although this can vary from borough to borough.

Interventions, such as linear rain gardens as we designed on our project for the Guide Dogs for the Blind Association, can perform several functions simultaneously: separating pedestrians from vehicles, managing surface water as part of the site’s drainage strategy, and increasing planting opportunities — thereby improving the project’s UGF score.

In practice, the Urban Greening Factor operates as a positive iterative planning policy tool that helps to push clients and developers to maximize on site urban greening with an onus on integrated blue and green infrastructure systems.

As with Biodiversity Net Gain, how the planning red line is drawn can dramatically affect the overall score, but unlike BNG, the Urban Greening Factor is only a material consideration at planning rather than being a mandatory, statutory requirement under the Environment Act 2021.

Biodiversity Net Gain

Biodiversity Net Gain (BNG) is a mandatory strategy in England’s planning system that ensures new developments contribute to the recovery of nature. Under the Environment Act 2021, developers must deliver a measurable 10% increase in biodiversity compared to the site’s original state.

Effective from 2024, it seeks to ensure that development leaves the environment in a better state with improvements that are secured for at least 30 years, achieved on-site, off-site, or via statutory credits.

Key Aspects of BNG

– Mandatory Requirement: A 10% gain is required for most developments to receive planning permission.
– The Mitigation Hierarchy: Developers must follow a specific order of steps: avoid, minimize, remediate, and only then compensate for biodiversity losses.
– Measurement: A statutory biodiversity metric is used to calculate the value of habitats before and after development, ensuring a measurable gain.
– Delivery Methods: BNG can be achieved through on-site habitat creation, off-site enhancements, or as a last resort, purchasing national biodiversity credits.
– Long-Term Management: Created or enhanced habitats must be secured and managed for a minimum of 30 years.

The Biodiversity Gain Hierarchy

Developers must follow a specific order of priority when meeting their 10% target:
– On-site Gains: Enhance or create habitats within the development’s boundary (the preferred method).
– Off-site Gains: If on-site is not possible, developers can create habitat on their other land or buy “units” from a biodiversity gain site – refer to links at the end of this article.
– Statutory Credits: As a last resort, developers can buy credits from the government, which uses the funds for habitat creation.

Exemptions and Implementation

While most developments require BNG, some exceptions apply, such as small-scale self-build projects or developments below certain size thresholds.

Developers must submit a Biodiversity Gain Plan as part of the planning process to demonstrate how they will meet the 10% requirement. Local Planning Authorities are responsible for approving these plans.
Biodiversity Net Gain (BNG) calculations in the UK must be carried out by a “competent person,” typically a qualified ecologist or environmental consultant, using the statutory biodiversity metric.

Key considerations

Existing trees, particularly native species, score highly in the BNG baseline, and their potential removal greatly affects the post-development value. Simply planting new trees rarely replaces the high biodiversity value of mature specimens; therefore, retaining existing, high-value trees is strongly prioritized to meet BNG requirements.

Early Challenges

While BNG represents a landmark environmental policy, its implementation has not been without challenges.

– There have been resource and capacity gaps across often overstretched planning departments, leading to delays in processing applications due to the additional administrative burden of BNG.
– There are some concerns over how local planning authorities will monitor and enforce the 30 year obligation period, with potential risk of non-delivery, especially for myriads of small sites.
– From a design perspective, the reliance on numerical metrics can sometimes encourage a “design by numbers” approach. Landscape architects must balance ecological targets with the creation of meaningful, people-centred places, and this requires all consultants working together rather than in silos.
– The impact on small sites was not properly thought through. The ‘de-minimis’ threshold was set far too low (25m²) as it is much more difficult to deliver BNG on small sites, and the cost of the BNG process (for applicants and local authority) can outweigh the benefits delivered.
– Social injustice – the biodiversity gains may be delivered far from the community impacted by a development, meaning local residents lose access to nature while the benefits are “offset” elsewhere. Local authorities did hope to create habitat banks within the local parks to the developments, but that has proved too difficult.

Proposed changes

The Government undertook a review of BNG in the summer of 2024, and it has since signalled some key changes to BNG that will come into effect potentially in 2026, should Parliamentary time allow the amendments to the primary legislation.

– Sites under 0.2Ha will be exempt from BNG – the ‘de-minimis’ threshold is proposed to be increased from below 25m² to a more sensible 0.2Ha minimum area.
– It is likely that brownfield residential developments up to 2.5 hectares will be exempt from BNG
– Developments whose purpose is for nature conservation may well be exempt
– Development of Parks, public gardens and playing fields may be exempt in the future rather than having to deliver 10%

A Step in the Right Direction

Despite these early challenges, Biodiversity Net Gain represents an important step forward.
The UK remains one of the most nature-depleted countries in the world. Policies that embed ecological recovery within the development process are therefore essential if we are to restore biodiversity while continuing to build our cities – England and Wales adopted BNG in 2024, and Scotland is due to bring in their own BNG version in 2027.

BNG does not solve every problem, but it establishes a clear principle: development should leave nature in a better condition than it found it. For landscape architects, that principle offers both a responsibility and an opportunity. This ‘design by numbers’ approach relies heavily on quantitative targets, metrics, and scoring systems rather than holistic or creative landscape design – hitting required ‘scores’ rather than thinking more broadly about how a place works for BOTH people, and nature!