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.  

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. Within settlement limits, greenfield land can also be zoned for development (eg housing). 

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 

Greenfield land in Northern Ireland includes both land within settlement development limits and countryside beyond. 

Within settlement limits, housing on greenfield land is typically built at lower densities than city or town centre land 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, appropriately designed greenfield sites do present opportunities to include extensive nature-rich natural greenspace within new developments and increase the site’s biodiversity value.  

Outside of settlement limits, housing on greenfield land is small scale usually comprising one or two units and is usually only permitted in certain circumstances which are set out in policy – eg an infill dwelling or a dwelling on a farm. These are generally referred to as ‘acceptable in principle’ types of development, but they must also satisfy a number of other policy provisions to be approved. Each local planning authority (LPA) will have its own list of acceptable in principle developments in the countryside.  

For all other types of developments (that are not included within the LPA’s acceptable in principle list), unless allocated for development in the local development plan, the applicant will need to demonstrate that there are overriding reasons why the development proposed is essential and could not therefore be located within a settlement.  

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 many 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.  

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 development plan or in a planning application, here’s what to look out for: 
 

• Check to see if a biodiversity checklist has been completed and whether a Preliminary Ecological Assessment was considered necessary. This will inform the need for other ecological surveys. If it hasn’t then ask the LPA 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. See our guide for more information on ecological assessments (link below).  

• 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). See this DAERA advice for more information.  

• 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, the mitigation hierarchy approach should be applied. Impacts caused by the development should be avoided wherever possible (eg by looking for alternative sites or redesigning the scheme), followed by the mitigation of any impacts that can’t be avoided. Surveys should outline any mitigation measures 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