Greenfield vs brownfield land: what does it mean?

Last updated: 2 July 2025

Greenfield and brownfield land are familiar terms used in the planning world, but the wildlife interests of these different sites might come as a surprise. 

The term greenfield land will most likely conjure up images of the countryside, untouched by development and teeming with wildlife, whereas by contrast, brownfield land is often associated more with ex-industrial sites and urban areas.  

But what many of us might not know, is that brownfield sites that have been left in a semi-natural state can be more wildlife-rich than some greenfield sites. For example, agricultural land that has been intensively used will often have limited biodiversity value, despite its greenfield status. Meanwhile, an abandoned brownfield site can contain a mosaic of habitats that are attractive to a whole range of wildlife, including invertebrates of locally or nationally high conservation value. 

Therefore, we need to make sure that all the necessary ecological assessments are carried out for development proposals on brownfield sites. We don’t want any assumptions that the site has no value for wildlife, just because it’s brownfield! 

Before we explore the planning issues associated with greenfield and brownfield land, let’s define what the two terms actually mean. The term ‘Green Belt’ is also explained below for clarity.  

Greenfield land (or a defined greenfield site) is land that has not been built on before. It is usually found in rural/countryside areas but can also be found in more urban areas in the form of parks, playing fields and allotments.  

Brownfield land is a site that has been built on or altered by human activity before (also known as previously-developed land). It includes land which is or was occupied by a permanent structure, including the curtilage of the developed land and any associated fixed surface infrastructure. Quarries and sand/gravel pits are also classed as brownfield land.  

However, there are some exceptions to this, which include:

• Land that is or has been occupied by agricultural or forestry buildings.
• Land that has been developed for minerals extraction or waste disposal by landfill. purposes where provision for restoration has been made.
• Land in built-up areas such as private residential gardens.
• Parks, recreation grounds and allotments.
• Land that was previously developed but where the remains of the permanent structure or fixed surface structure have blended into the landscape in the process of time. 

You may also have heard the term ‘Green Belt’ so it’s worth outlining this here for clarity. ‘Green Belt’ should not be confused with ‘greenfield’ land. 

Greenfield is a land use description whereas the Green Belt is a planning policy designation for land surrounding some urban areas. Green Belt designation covers land in a variety of uses and includes both brownfield and greenfield sites.

Essentially, the Green Belt is a policy for controlling urban growth and takes the form of a ring of countryside around some towns and cities. It was first introduced in the 1930s to limit urban sprawl around London. 

There are currently 14 Green Belts in England which cover almost 13% of the country’s land area. CPRE, the countryside charity (formerly known as The Campaign to Protect Rural England) is the leading organisation campaigning on Green Belt issues in England and publishes a range of useful resources if you want to find out more (search in the ‘About us’ section of their website here). 

There are 11 Green Belts in Scotland and 1 in Wales. Northern Ireland has no Green Belt designations.  

In December 2024, the Government introduced the concept of ‘grey belt’ through the updated National Planning Policy Framework (NPPF). Grey belt refers to areas within the Green Belt that consist of previously developed land or land that makes a limited contribution to the Green Belt's intended purposes. 

Local planning authorities are responsible for allocating grey belt development land in very special circumstances. Areas of particular importance, such as sites with environmental designations, are excluded from grey belt allocation.  

To find out more about grey belt, take a look at the Green Belt planning practice guidance. 

Housing on greenfield land is typically built at lower densities and may be harder to integrate with existing communities and infrastructure.  

Greenfield developments can have other disadvantages such as soil sealing (the covering of the ground by an impermeable material such as concrete or tarmac) which may have implications for flood risk, and the loss of agricultural land. The loss of countryside often makes them unpopular with local communities too.  

On the other hand, greenfield sites do present opportunities to include extensive natural greenspace within new developments and may replace intensively used agricultural land that has limited biodiversity value.  

National planning policy generally favours brownfield land for development over greenfield land, as it is widely seen as having a number of sustainability advantages such as: 

• By reusing land it reduces the conversion of undeveloped land (usually farmland) to urban uses.

• It often provides better access to existing facilities such as shops and schools, therefore reducing travel costs and carbon emissions.

• In urban areas it can be developed at higher densities, which reduces the amount of land required for a given number of homes and generally also has lower carbon costs.

However, in some cases brownfield land can harbour biodiversity of significant value which needs to be carefully assessed and protected. 

Brownfield sites in urban areas that are left in a semi-natural state not only provide significant biodiversity benefits but can also help people and the environment in the following ways: 

• Climate cooling 

• Noise reduction 

• Flood mitigation 

• Capturing/storing carbon dioxide (CO2)  

• Access to nature and greenspace 

It is important to consider the pros and cons of each individual site, whether it comprises greenfield or brownfield land.  

The environmental costs and benefits of development on greenfield or brownfield land are complex. Much depends on the form of development and the uses it is replacing.  

The RSPB takes a biodiversity-led approach to questions of greenfield vs brownfield. It is acknowledged that brownfield development has some sustainability advantages, however biodiversity of significant value must be protected wherever it is found, and adequate provision of accessible wildlife-rich greenspace must be made in all developments.  

With regards to the Green Belt, the RSPB welcomes the additional protection it indirectly provides for nature. However, as we do not consider it to be primarily an environmental policy, we feel that other organisations such as the CPRE are better placed to engage with Green Belt policy issues.  

The biodiversity value of a brownfield site can often be overlooked. We need to make sure that this doesn’t happen!  

When a brownfield site is proposed for development, either as an allocated site in a local plan or in a planning application, here’s what to look out for: 

• Check to see whether an ecological survey has been carried out. If it hasn’t, then ask the local planning authority to request one from the applicant. If the site contains structures, it may be home to bats or nesting birds, and if it has returned to a semi-natural state then it may be supporting reptiles or other wildlife.  

• If ecological assessments have been submitted, make sure that the surveys have been carried out at the correct times of the day/year for that particular species (eg, the best time to survey for breeding birds or flowering plants is early spring to late summer in the early morning or evening). 

• Compare the findings with your own local knowledge and experiences of the site. Make the Planning Officer aware of any discrepancies between the submitted information and your own evidence.   

• If a survey identifies the presence of protected species, adequate mitigation for any impacts caused by the development must be proposed, as well as enhancements. If this is not the case, make the Planning Officer aware of this.  

• Depending on the scale of the development, an Environmental Impact Assessment (EIA) may be required to identify the effects of the proposal on the environment. See our guide for more information on the EIA process (link below) 

Buglife’s Brownfield Hub  

What is an ecological assessment and when is it needed?

An overview of Environmental Impact Assessment