Conservation often conjures images of small nature reserves, protected woodlands, or wildflower meadows. But increasingly, experts argue that conservation must operate at much larger scales, covering landscapes, networks, and even entire regions. When habitat is too small, fragmented, or isolated, even good quality nature reserves struggle.

But how big do wildlife restoration projects and conservation areas need to be? When it comes to green space, what do we know, what remains uncertain, and where should our efforts focus?

Why scale matters for nature restoration projects

When the natural world is protected only in tiny patches, fragmentation reduces sites’ viability. A small, isolated conservation area can’t support viable populations of many species. Genetic diversity declines, reproductive success drops, and changes in biological structure at the edges of nature reserves can degrade habitat quality.

  • Connectivity is essential. Species often move seasonally to seek food or to breed, but barriers such as roads, urban areas or farmland can restrict that movement. If habitat patches are too far apart, or the surrounding environment is too hostile, movement and genetic strength suffer.
  • In a conservation area, factors such as predation, competition, carbon storage and water systems often function properly over large tracts of land comprising good quality green and blue spaces. Green space helps counter carbon emissions by acting as a carbon sink and storing carbon in soil.
Common dormice need areas of good quality connected habitat in rural areas to survive.

Nature restoration projects: UK case studies

The NatureScot Research Report 1271 examines large-scale nature restoration and rewilding case studies. It states that restoring connected landscapes rather than disconnected small sites brings greater benefits for species richness, connectivity, and ecosystem services.

Connectivity networks in England were scrutinised in a research article in the Royal Society Publishing titled “Habitat patches providing south-north connectivity are under-protected in a fragmented landscape.”

It found that many areas important for enabling species’ range to extend due to climate change are not protected, and that protecting these would significantly improve connectivity with only modest increases in the size of the protected area of green space.

The article stated:

We find high-flow patches are often left out of existing protected areas … Across 12 of 16 habitat networks, connectivity protection falls short of area protection by 13.6% on average.

Special nature reserve: The Lake District.

A conservation area needs size for biodiversity

Researchers from Nottingham Trent University in a study published in March 2025, reinforced the idea that size matters when it comes to nature reserves and preserving species. The report, titled: “Want to preserve biodiversity? Go big, researchers say” found that larger continuous habitat incorporating green and blue spaces offers most if not all the benefits needed to support more species and more stable populations.

It stated:

Large, undisturbed forests are better for harbouring biodiversity than fragmented landscapes.

The Wildlife Trusts have set a `30by30’ target: to protect 30% of land and sea for nature by 2030. This is a national and global policy aim, partly because cumulative evidence shows that below certain thresholds of habitat protection and habitat cover, species decline accelerates.

What is a viable size for restoration projects?

  • Large areas and corridors: Rather than many disconnected small nature reserves, a mix of large core areas plus linking corridors with tree cover and different vegetation type categories between them creates the best outcomes.
  • Thresholds of habitat cover: Some studies suggest that once habitat cover in a landscape drops below 30%, fragmentation effects such as loss of connectivity and local extinctions, increase sharply. So, as a first step, it’s often proposed to restore habitat cover up toward or above this threshold.
  • Spatial modelling to identify priority areas: The studies noted above show that not every area is equally important: some locations act as stepping stones or hubs in green infrastructure networks that facilitate species movement.
The natural world: nature reserves are vital to many protected species including the red squirrel.

Access to urban green space benefits local communities

Having public green space near to urban areas provides a host of benefits and is an important factor in local government strategies. Access to the natural environment is known to play an important role in supporting people’s health and wellbeing and help those experiencing mental illness.

Research shows that increasing public access to urban green space boosts people’s mental health. For towns and cities in deprived areas with a lack of urban green space, green infrastructure, or community gardens, there may be air pollution issues. The opportunity to spend time in natural surroundings can lower incidence of many community health conditions for both older and young people.

The mental health benefits include improved air quality and the opportunity for physical activity which is important when there may be limited access to public green space in urban environments. As well as being beneficial for peoples’ mental wellbeing, access to the natural environment and healthy places can alleviate chronic diseases and different types of human health issues.

Green space in built-up areas also counters the urban heat island effect that the built environment creates. As well as green gentrification and green space such as urban parks, green roofs can help alleviate heat island issues in cities. This can result in reduced risks of problems with increased temperatures in the summer months, and will often be encouraged by a local council.

Other reasons for increasing access to green space in towns, cities and other places include general public health; parks offer a chance for social interaction, human activity and social cohesion in a local area as well as the opportunity to bring nature into the landscape.

Scaling up nature reserves: the trade-offs

While larger tracts of green space in rural areas appear to be most beneficial, scaling up UK conservation areas and nature restoration projects involves compromises:

The pros:

  • Greater resilience. Larger connected habitats are more able to withstand storms, fire and climate extremes.
  • More species and more stable populations: wide-ranging species, predators or pollinators may need larger ranges.
  • Carbon storage, flood mitigation and water purification are more effective over broad catchment scales.

The cons:

  • Large tracts of land are expensive and converting agricultural or other productive land has economic and social consequences.
  • Usually, land is privately owned: coordinating across landowners is complex, requiring incentives or compensation to create conservation areas.
  • Landowners and local communities may resist conservation areas that limit land use such as grazing or new development, and be concerned about impacts from predators.
  • Large areas of green space need proper management such as invasive species control and connectivity route monitoring.
Important green space: peatland in the Forsinard Reserve, Scotland.

Scaling up in practice

How is this playing out on the ground in UK policy and conservation practice?

  • The UK has increased its formally protected areas of land and sea, but many are in poor condition, fragmented, or have compromised connectivity.
  • Several large-scale restoration initiatives are underway including peat restoration, planting tree species, woodland expansion and nature corridors. The National Trust’s recent projects, work by other trusts and government funding for habitat networks indicate that scaling is becoming part of mainstream conservation. The Trust aims to provide greater public access to nature and green space; enabling more people to enjoy the natural environment where there is land designated as open spaces is a recognised way of improving people’s health and well being.
  • The UK government has committed to protect 30% of land and seas by 2030, however, the British Ecological Society states that the term “protect” needs to mean effective protection leading to well-managed, connected, and ecologically viable areas.

Nature reserves: the unknowns

There are still grey areas in the science, such as:

  • The optimal area of green space for many species is unknown: for some insects, small patches of green space may suffice; for mammals even large reserves might be too small.
  • Trade-offs between quality and size: high-quality small nature reserves may find they outperform a larger but degraded area, complicating funding allocations.
  • Scale of management versus scale of protection: even when large areas are protected, management is resource intensive. Sometimes small sites with high investment perform at higher levels compared to larger, poorly managed ones.
  • Land use pressures on green space: housing demand, farming and infrastructure all compete.
Precious places in the natural environment: open spaces in the Cairngorms National Park.

Examples of scaling up

  • Covering 600 square kilometres, Cairngorms Connect is a fascinating nature reserve and the biggest habitat restoration project in Britain.
  • Cornwall Wildlife Trust’s Tor-to-Shore initiative aims to link land and sea by rewilding, creating conservation corridors and marine conservation work.
  • The National Trust’s Turning the Tide for Nature initiative involves thousands of hectares of green space where wetlands, bogs and wood pasture will be restored.
  • The Wildlife Trusts’ 30by30 campaign aims to ensure that land protected by 2030 meets the scale and quality needed for real biodiversity gains.
Green space: the Coaley Peak Nature Reserve in the Cotswolds.

So, how big should nature reserves be?

Based on current evidence, British nature reserves find:

  • A connected landscape of 10,000-100,000 hectares (or more) is likely necessary to support wide-ranging mammals, woodland interior specialists and resilient habitat networks.
  • There will be local variations: what works in the uplands, heathlands, peatlands, valleys, or urban fringe will differ. But the components of size, quality, connectivity and long-term management are the benchmarks for success when it comes to green open spaces or blue spaces.

Large restoration projects outperform fragmented areas

In conservation, while size cannot guarantee success, it changes the game when it comes to green space. Small, well-managed reserves will have local value, but many of our ecological crises demand landscape-scale action. The question isn’t just one of size, it’s also how connected, resilient and durable nature reserves are.

A successful wildlife conservation area must be big enough to allow nature to roam, regenerate and adjust. If we only protect pockets of green space surrounded by hostile land, many species, especially those sensitive to disturbance, may still fall between the cracks.