An analysis of ecological connectivity in London using terrestrial habitat-proxy species

In the heart of a bustling city, nature does not stop at the edge of a park or the boundary of a neighborhood. It flows through the cracks in the pavement, along the lines of street trees, and across the rooftops, connecting the wild and the domestic in a complex web. For decades, scientists and city planners have tried to measure the health of these urban ecosystems, often relying on simple counts: how much green space exists, or how many trees cover the ground. These structural measurements are easy to see and map, but they tell only part of the story. They show where the green is, but not how animals actually move through it. To truly understand if a city can support wildlife, one must look beyond the static picture of vegetation and ask a more functional question: can a creature get from one patch of habitat to another without getting lost or blocked? This is the realm of landscape ecology, a field that treats cities not as collections of separate parks, but as interconnected landscapes where the movement of life is just as important as the presence of life itself.

A recent study by Thomas O'Callaghan-Brown at the University of Oxford takes this functional approach to the city of London, challenging the way the city currently measures and manages its nature. Instead of simply counting acres of grass or trees, the researcher used a computer model to simulate how four different types of animals would navigate the city. These animals were chosen as "proxy species," standing in for larger groups of wildlife with similar needs. The group included the European badger and the European stag beetle, which rely on woodlands, and the European hedgehog and the small heath butterfly, which prefer grasslands. Within each pair, one animal is a generalist, comfortable in many different environments, while the other is a specialist, requiring very specific conditions to survive. By running these simulations across the entire city, the study mapped out the invisible pathways that connect habitats, revealing where animals can move freely and where they are forced into narrow, dangerous bottlenecks.

The results of this functional map offered a surprising contrast to the city's official green rankings. London's current environmental strategies prioritize areas based on the percentage of green space and tree canopy cover. However, when the researcher compared these official rankings with the movement patterns of the simulated animals, the two lists did not match. A borough that looked very green on a standard map was not necessarily a good place for a specialist animal to travel through. For instance, the borough of Kensington and Chelsea ranked very low for overall green space and tree cover, yet it emerged as a critical hub for the movement of badgers and stag beetles. Conversely, some of the greenest boroughs were less important for connecting the wider network of wildlife habitats. This suggests that simply having a lot of greenery does not guarantee that it is useful for the animals that need to move between different parts of the city.

The study also highlighted a significant gap in how city governance handles nature. London is divided into 32 separate administrative districts, or boroughs, each with its own council and environmental plans. The simulation revealed that a substantial portion of the movement for these animals crosses these political boundaries. For the woodland species, more than 10 percent of their total movement occurred across borough lines. Even for the grassland species, a significant amount of travel happened between districts. This finding underscores a critical reality: nature does not respect the lines drawn on a map by human governments. When policies are made in isolation by a single borough, they risk missing the larger connections that keep the city's wildlife alive. The study identified specific "pinch points"—narrow corridors where the flow of animals is concentrated—which could be targeted for protection to ensure the network remains intact.

Perhaps the most striking discovery was that the standard measures of green space and tree cover were poor predictors of how well the city functions for specialist species. While generalist animals, like the hedgehog, could navigate the city reasonably well even in areas with less green cover, the specialists, such as the stag beetle, struggled in areas that looked green on paper but lacked the specific connections they needed. The correlation between the amount of green space and the ability of these specialists to move was weak. This indicates that a city could be full of parks and trees and still fail to support the most vulnerable wildlife if those green spaces are not linked together in a way that allows for safe passage. The study suggests that to build a truly "nature-smart" city, planners must move beyond counting acres and start designing for movement, ensuring that the functional connections between habitats are preserved across administrative boundaries.

By treating the city as a living, moving system rather than a static collection of green patches, this research offers a new way to think about urban conservation. It demonstrates that the value of a piece of land depends not just on what is growing there, but on where it leads. For London, and for cities around the world, this means that protecting nature requires a level of cooperation that crosses political lines. It calls for a shift in policy from managing isolated pockets of nature to managing the entire landscape as a connected whole. If cities are to remain places where both people and wildlife can thrive, the invisible highways of the natural world must be recognized, mapped, and protected with the same care given to the roads and bridges of the human world.