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 reserves struggle. But how big is “big enough”?

What do we know, what remains uncertain, and where should efforts focus?

Why scale really does matter

When nature is protected only in tiny patches, fragmentation reduces sites’ viability. Small, isolated areas can’t support viable populations of many species. Genetic diversity declines, reproductive success drops, and changes in biological structure at the site edges 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.
  • Ecological processes scale up. Factors such as predation, competition, carbon storage and hydrology often function properly (or optimally) over large areas. Small areas may fail to sustain ecological dynamics.

For these reasons, many conservation scientists and organisations argue scale is essential if conservation is to succeed long-term.

Common dormice need areas of connected habitat to enable their survival.

What research tells us: models, case studies and targets

Recent research, including UK-based studies, gives us insights into the scale that’s needed and the factors that matter when deciding.

UK case studies and landscape-level restoration

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. Scale in these projects often involves thousands of hectares.

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.

The research 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.

This suggests that even protected areas may not be addressing the most critical areas for movement and climate resilience.

Research-based findings on size and biodiversity

A study featured in ScienceDirect investigating ponds in Switzerland compared pond size to diversity of aquatic plants, molluscs, insects and amphibians. It found that larger ponds had significantly greater species richness. Size here explained up to approximately 30% of variability in species richness for those groups.

Researchers from Nottingham Trent University in a study published in March 2025, reinforced the idea that size matters when it comes to preserving species. The report, titled: “Want to preserve biodiversity? Go big, researchers say” found that larger continuous habitat supports more species and more stable populations.

It stated:

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

Policy targets

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.

So, what is a viable size for a conservation area?

  • Large areas and corridors: Rather than many disconnected small reserves, a mix of large core areas plus linking corridors between them creates the best outcomes. This allows species movement and a buffer from problematic issues at site edges and climate shifts.
  • 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, it’s often proposed to restore habitat cover up toward or above this threshold: `30by30’ is based partly on this theory. But it’s not just percentage area; it’s also the quality of habitat, its configuration and connectivity.
  • 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 networks that facilitate species movement. Protecting or restoring those areas can yield good results.

Trade-offs, limitations and social factors

While larger tracts of land appear to be most beneficial, scaling up conservation involves trade-offs: here are the main pros and cons.

The pros:

  • Greater resilience. Larger connected habitats are more able to withstand disturbance from, for example, storms, fire and climate extremes.
  • More species and more stable populations. Particularly for wide-ranging species, predators or pollinators that need larger ranges.
  • Ecosystem services at scale. Carbon storage, flood mitigation and water purification are more effective over broad catchment scales.

The cons:

  • Land cost / opportunity cost. Large tracts of land are expensive and converting agricultural or other productive land has economic and social consequences.
  • Land ownership complexity. In many countries, including the UK, land is privately owned in fragmented parcels. Coordinating across landowners is complex, requiring incentives or compensation.
  • Social acceptance and stakeholder conflict. Farmers, landowners and local communities may resist conservation that limits land use such as grazing or development. There may also be worries about wildlife impacts, for example from predators and crop damage.
  • Management and maintenance. To maintain good habitat quality, large spaces need proper management which might involve invasive species control and monitoring of connectivity routes.
Peatland in the Forsinard Reserve, Scotland.

UK policy and initiatives: scaling up in practice

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

  • More protected areas: The UK has increased its formally protected areas of land and sea, but many protected areas are in poor condition or are small, fragmented, or have compromised connectivity.
  • Nature restoration and rewilding programmes: Several large-scale restoration initiatives are underway including peat restoration, woodland expansion and nature corridors. The National Trust’s recent projects, other trusts and government funding for habitat networks indicate that scaling is becoming part of mainstream conservation.
  • 30by30 commitment: 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 of land and sea.

What is still unknown

Despite progress, there are grey areas in the science:

  • Optimal area size for many species is unknown: For some insects, small patches may suffice; for mammals (especially large or wide-ranging) even large reserves might be too small. Data gaps remain.
  • Trade-offs between quality and size: A very high-quality small reserve may outperform a larger but degraded area. When budget is limited, it raises the question of where efforts should be directed first.
  • Scale of management versus scale of protection: Even when large areas are protected, management (restoration, controlling invasive species, ensuring connectivity) is resource intensive. Sometimes small sites with high investment outperform larger but poorly managed ones.
  • Social and economic limits: Land use pressures, housing demand, farming, infrastructure all compete. Scaling up requires navigating social, political, legal and economic constraints.
The Cairngorms National Park.

Case examples: scaling up in action

  • Covering 600 square kilometres, Cairngorms Connect is the biggest habitat restoration project in Britain.
  • Cornwall Wildlife Trust’s Tor-to-Shore initiative aims to link the land to the sea; it   involves rewilding, creating conservation corridors and marine conservation work.
  • The National Trust’s Turning the Tide for Nature initiative involves many thousands of hectares where wetlands, bogs and wood pasture will be restored to create ecological and climate benefits.
  • The Wildlife Trusts’ 30by30 campaign aims to ensure that land protected by 2030 meets the scale and quality needed for real biodiversity gains.

So, how big is “big enough?”

Based on current evidence, here’s what “big enough” might look like for many British conservation scenarios:

  • 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. For smaller species like insects and plants, smaller patches matter, but only when they are connected and embedded in landscapes with sufficient habitat cover. Regions or networks achieving 30% habitat cover, with wildlife corridors and high quality replanted or restored areas will be much more resilient.
  • Importantly, “big enough” will vary locally: what works in the uplands, heathlands, peatlands, valleys, or urban fringe will differ. But the principle holds: the components of size, quality, connectivity and long-term management are the benchmarks for success.

Large expanses outperform fragmented areas

In conservation, while size cannot guarantee success, it changes the game. A small, well-managed reserve will have local value. But many of the ecological crises we face – declining pollinators, loss of forest species, range shifts under climate change – demand landscape-scale action. The question isn’t only “How big?” but “How connected, how resilient and how durable?”

A successful conservation area must be big enough to allow nature to roam, regenerate and adjust. If we only protect islands in a sea of hostile land, many species, especially those sensitive to disturbance, may still fall between the cracks.