The swift problem: when a species' habitat is the building, green infrastructure misses it

A new study comparing how urban planning takes nature into account concludes that the standard instruments, environmental offsetting, sustainable development and nature-based solutions such as green roofs, street trees and wetlands, have become good at demonstrating what nature does for people and much less willing to ask whether other species have interests of their own ^[1][2]. The gap bites hardest for animals whose habitat is the building fabric: UK swift numbers have fallen by around 60% since 1995, and in 2021 the species was added to a list of birds at greatest risk of extinction ^[3][4].

Swifts nest in gaps under eaves and roof tiles, and those gaps can disappear when older buildings are demolished, re-roofed or insulated, according to the researcher writing at phys.org ^[5]. That is the awkward case for the toolkit. A 60% decline leaves the population at roughly two-fifths of its 1995 level ^[6], and the usual levers do not reach the cause. Nothing about a street tree, a wetland or an offset elsewhere restores a cavity closed during a retrofit.

The study's diagnosis is about justification rather than intent. Trees get planted because they cool streets, wetlands get protected because they hold floodwater, parks get funded because they improve human health ^[7]. Those benefits are real, the author writes, but they leave nature looking like a service provider, which raises the question of what remains of the protective argument when a tree no longer provides enough shade or a wetland becomes more valuable as development land ^[8]. The alternative framing offered, multispecies justice, starts from the premise that animals, plants and ecosystems are co-inhabitants rather than amenities ^[9].

In practice the author asks for changes to decision inputs, not for wildlife reserves: judging a river restoration partly on whether fish and frogs are likely to thrive in it, designing developments around established wildlife routes instead of treating them as obstacles to mitigate later, extending environmental assessment of a new road to badger and bat routes alongside drainage and emissions, and leaving some places undisturbed during breeding seasons ^[10][11].

Precedents exist, with caveats the author states plainly. New Zealand's Whanganui River was recognised as a legal person in 2017 with guardians appointed to represent its interests, and Colombia's Atrato River was recognised as a subject of rights in 2016 under a similar guardianship system ^[12][13]. Those rights still have to operate inside existing political and legal systems, and research suggests implementation in Colombia has been uneven ^[14]. Barcelona has built green corridors linking parks to the hills beyond the city so wildlife can move through ^[15].

The cheapest intervention in the study is regulatory. Scotland is the first nation to require swift bricks by law in new buildings; the bricks are hollow, contain a nesting cavity, and cost roughly 30 pounds each ^[16][17]. The author's point is that the mandate reclassifies another species from an unexpected problem into a design input ^[18]. With more than half the world's population now living in urban areas and cities still expanding into wildlife habitat, the classification is doing more work than the hardware ^[19].

Two things to track. First, England: the account we have breaks off mid-sentence on attempts to require swift bricks there by law, so the outcome is not established in this source ^[20]. Second, whether Scotland's requirement is audited for occupancy rather than installation, since a mandated cavity and an occupied one are different measurements, and only the second bears on the 60% ^[3].