The Wild Between: Habitat Corridors and the Connected City

There is a hedgehog somewhere near you, right now, nose to a fence panel. On the other side lies everything it needs; beetles, a mate, a dry corner to nest; and between the two, six feet of larch-lap and a concrete gravel board. To us it is a boundary. To the hedgehog it is the edge of the world.

This is the quiet tragedy of the modern town: not that we have banished nature, but that we have chopped it into pieces too small to live in. Rewilding the city is often imagined as adding - more meadows, more trees, more ponds. And it is that. But the deeper work, the work that turns a scattering of green patches into something a living system can actually use, is joining. It is the wild between.

Islands are where wildness disappears

Ecologists have a bleak phrase for what happens when habitat is broken up: fragmentation. A wood becomes a copse becomes a lone oak in a car park. A meadow becomes a verge. Each surviving fragment holds a smaller population, and small populations are fragile ones. Cut off from their neighbours, they can't top up their numbers after a bad winter, can't find unrelated mates, can't recolonise once local disaster strikes. Genetic diversity narrows. Isolation, slowly, becomes extinction.

The response — the idea at the heart of this whole blog — is deceptively simple. If you reconnect the fragments, you give life its options back. A habitat corridor is any strip or stepping-stone of living ground that lets a creature move from one patch to another: a hedgerow, a railway embankment, a chain of wildlife-friendly gardens, a river and its banks, a ribbon of long grass through a mown park. The corridor itself need not be a whole habitat. It needs only to be passable.

Does it actually work? The evidence says yes

This is where a good rewilding article earns its keep, because "connect nature and nature recovers" sounds like the kind of thing that ought to be true but might just be wishful. It isn't. It is one of the better-tested propositions in conservation science.

A landmark meta-analysis by Gilbert-Norton and colleagues, published in Conservation Biology in 2010, pooled 78 experiments from 35 separate studies and asked a blunt question: do corridors move animals and plants between patches, or don't they? The answer was a clear yes; connected habitats saw roughly half as much again in movement compared with unconnected ones, and, tellingly, purpose-built corridors outperformed accidental ones.

Movement is the mechanism. The prize is what it produces over time. In one of ecology's great slow experiments, researchers in South Carolina restored patches of open savannah and linked some of them with corridors while leaving others stranded. Reporting eighteen years of results in Science in 2019, Damschen and colleagues found that the connected patches steadily gained plant species the isolated ones did not — a compounding advantage that reached around 14% more species and, remarkably, showed no sign of levelling off. Connection didn't just hold the line. It let diversity accumulate, year on year.

And the benefit reaches down into the genes. Work by Christie and Knowles has shown that corridors help maintain genetic resilience across populations more or less regardless of how far a species can disperse on its own — the connective tissue matters even for the homebodies.

Why cities, specifically, need the threads

You might reasonably ask whether findings from savannahs and nature reserves translate to a landscape of cul-de-sacs and retail parks. They do — and here the most useful single study is a global meta-analysis by Beninde, Veith and Hochkirch, published in Ecology Letters in 2015, which combed the evidence from 75 cities worldwide to ask what actually predicts biodiversity within an urban area. Of all the variables they tested, two stood out above the rest: the size of green patches and the corridors between them. Their conclusion was unambiguous — the single most important strategy for keeping cities rich in life is to make habitat patches bigger and to weave them together with a network of corridors.

Read that again, because it reframes the whole task. In the city, connection isn't a nice-to-have that comes after the "real" habitat is built. It is the real habitat.

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More, bigger, better and joined"

Britain arrived at the same conclusion from the policy direction. In 2010, Professor Sir John Lawton's review of England's wildlife sites, Making Space for Nature, distilled everything the country needed to do for nature into four words: more, bigger, better and joined. That last word did a great deal of work. It has since become the backbone of the Nature Recovery Network and the Local Nature Recovery Strategies now being drawn up region by region — an explicit national attempt to stop managing wild places as a scatter of lonely islands and start managing them as a web.

The strategy scales all the way down. Which is the good news for anyone with a garden, a balcony, or a stretch of pavement they're allowed to plant.

From the map to your own back fence

Here is the part that matters most, because it is the part you can do this weekend.

Open the hedgehog highway. Hedgehogs roam one to two kilometres in a single night, quartering many gardens in search of food and mates; which is why a single tidy, sealed garden is useless to them, and a street of connected gardens is a lifeline. British hedgehog numbers have fallen somewhere between 30% and 75% since the year 2000, and in 2024 the western European hedgehog was listed as near threatened on the IUCN Red List. Habitat fragmentation through our ever more 'secure' fences and walls, is a prime culprit. The fix, championed by the Hedgehog Street campaign run by the People's Trust for Endangered Species and the British Hedgehog Preservation Society since 2011, is almost comically small: a 13cm by 13cm hole at the base of a fence, roughly the size of a CD case. Big enough for a hedgehog, too small for most pets. Cut one on each side of your plot and you have turned your garden from a dead end into a through-road. Ask your neighbours to do the same and you've started a corridor.

Plant a link in the pollinator chain. Many of our solitary bees will fly only around 300 metres to forage, so a lavish flowerbed marooned in a sea of decking and paving might as well be on the moon. The conservation charity Buglife has mapped a national network of B-Lines; three-kilometre-wide "insect pathways" threading through town and country alike precisely to solve this, with the aim of restoring 150,000 hectares of flower-rich habitat along them. It's a sobering context: England has lost around 97% of its flower-rich grassland since the 1930s. Your contribution is a border of single, open, nectar-rich flowers that bloom across the whole season, a patch of long grass, a few square metres left gloriously untidy. Each becomes a stepping stone. You can even check whether your home sits on a mapped B-Line and log what you plant.

Think in layers and ribbons, not islands. A native hedge outperforms a fence on every ecological measure...it is a corridor, a food source and a nesting site in one. A line of shrubs, a climber-clad wall, a strip of unmown grass linking one border to the next: these give smaller creatures continuous cover to travel under, which many will not cross open ground to reach. Even a chain of pots along a balcony rail are stepping stones for insects.

Don't forget the wet corridors. Frogs, toads, newts and dragonflies move along damp routes. A small pond, no bigger than a washing-up bowl, so long as it has a gentle exit ramp, plugs your garden into that hidden network. Ditches, rain gardens and boggy corners all count.

An honest word: corridors are not magic

Rewilding deserves clear eyes, so it's worth saying what the science also shows. Not every corridor works as hoped; the follow-up literature is full of well-meaning links that few animals actually used. Quality matters as much as connection; a strip of the right habitat, well managed and genuinely passable, beats a token green line every time. Poorly designed corridors can even carry unwelcome passengers, spreading invasive plants or disease. And connection can never substitute for the patches themselves: Beninde's team were equally emphatic that you need size as well as linkage. A corridor between two habitats too small to sustain anything simply joins two problems.

None of this is an argument against corridors. It is an argument for doing them thoughtfully - for asking not just "is it green?" but "can something actually live and travel here?"

The city as a living thing

The deepest shift urban rewilding asks of us is a shift in how we see. A city is not the built environment with a few parks tolerated inside it. It is, or could be, a single connected organism, but as a ''body'' whose gardens, verges, railways, rivers and rooftops are stitched together well enough for wildness to circulate through them like blood.

Every fence hole, every unmown metre, every native hedge and washing-bowl pond is one stitch in that fabric. On its own, a stitch does very little. Together, street by street, garden by garden, they become the wild between: the connective tissue that lets a fragmented, paved-over landscape breathe again, and turns a scattering of islands back into somewhere life can move.

The hedgehog is still stuck

at the fence. The question urban rewilding puts to each of us is whether we're going to cut the hole.

References & further reading

• Lawton, J.H. et al. (2010). Making Space for Nature: A Review of England's Wildlife Sites and Ecological Network. Report to Defra. (The "more, bigger, better and joined" review underpinning the Nature Recovery Network.)

• Gilbert-Norton, L., Wilson, R., Stevens, J.R. & Beard, K.H. (2010). A meta-analytic review of corridor effectiveness. Conservation Biology, 24(3), 660–668.

• Beninde, J., Veith, M. & Hochkirch, A. (2015). Biodiversity in cities needs space: a meta-analysis of factors determining intra-urban biodiversity variation. Ecology Letters, 18(6), 581–592.

• Damschen, E.I., Brudvig, L.A., Haddad, N.M. et al. (2019). Ongoing accumulation of plant diversity through habitat connectivity in an 18-year experiment. Science, 365(6460), 1478–1480.

• Christie, M.R. & Knowles, L.L. (2015). Habitat corridors facilitate genetic resilience irrespective of species dispersal abilities or population sizes. Evolutionary Applications, 8(5), 454–463.

• Buglife — B-Lines initiative. https://www.buglife.org.uk/our-work/b-lines/

• Hedgehog Street (People's Trust for Endangered Services & British Hedgehog Preservation Society). https://www.hedgehogstreet.org/

• Natural England / Defra — Nature Recovery Network and Local Nature Recovery Strategies.

• The Wildlife Trusts — How to create a hedgehog hole. https://www.wildlifetrusts.org/actions/how-create-hedgehog-hole