Practise all four skills, the right way

For centuries the European beaver was hunted almost to extinction, prized for its fur and for a glandular secretion used in perfume and medicine. By 1900 only a few hundred animals survived across the entire continent, scattered in isolated pockets from France to Siberia. The species had effectively vanished from Britain by the sixteenth century. For most people, the beaver became a creature of folklore rather than a living part of the landscape.

Recent decades have seen a remarkable reversal. Reintroduction programmes, some official and some unauthorised, have returned beavers to rivers across Europe. The results have surprised even the scientists who championed them. Beavers are what ecologists call a keystone species: by felling trees and building dams, a single family can reshape an entire stretch of river. The ponds they create slow the flow of water, trap sediment, and form wetlands that attract dragonflies, amphibians, fish and birds.

The benefits extend beyond wildlife. In several catchments, beaver wetlands have measurably reduced downstream flooding by holding back water during heavy rain and releasing it slowly. During droughts, the same ponds act as reservoirs. One long-term study in Devon found that water leaving a beaver-managed site was cleaner, with far lower levels of agricultural pollutants, than water entering it.

Not everyone is enthusiastic. Farmers whose fields border rivers sometimes find crops flooded or drainage channels blocked. Foresters lose valuable timber. Critics argue that reintroducing a species absent for four centuries amounts to gardening the wild rather than restoring it. Supporters counter that the modern landscape is already heavily managed, and that beavers simply do, for free, work that engineers would otherwise be paid to attempt.

What most observers now agree on is that coexistence requires management. Flow devices — pipes that limit how high a pond can rise — allow dams to remain while protecting roads and farmland. Where conflict is severe, animals can be trapped and moved rather than killed. The debate, in other words, has shifted from whether beavers should return to how their return should be governed.

A   In late spring, a healthy honey-bee colony often grows too large for its home. About half the workers, together with the old queen, then leave in a dramatic cloud and gather as a swarm — a beard of perhaps ten thousand bees hanging from a branch. The swarm now faces a problem on which its survival depends: within a day or two, with no map and no manager, it must choose a single new home from many possible cavities scattered across the landscape, and it must choose well. A cavity that is too small, too damp or too exposed will doom the colony.

B   The search is carried out by a few hundred experienced foragers acting as scouts. A scout that finds a candidate cavity inspects it carefully — walking its walls, measuring its volume — and then returns to the swarm and performs a waggle dance, the same code bees use to advertise flowers. The direction and length of the dance encode where the site is. Crucially, the better the scout judges the site to be, the more vigorously and the longer she dances. A mediocre site earns a brief, half-hearted performance; an excellent one earns minutes of enthusiastic repetition.

C   At first many sites are on offer, and rival groups of dancers advertise competing cavities at the same time. What stops the swarm splitting? Bees that have danced for one site go and inspect the sites others are advertising, and they dance for a site only as long as their own assessment supports it. Weak sites therefore lose their dancers quickly, while a genuinely good site keeps recruiting. Support drains from the poorer options and pools around the best one, so that over a few hours a clear favourite emerges without any bee comparing all the options itself.

D   The final commitment is triggered not by a majority but by a quorum. Scouts returning to a site count how many other scouts are already there. Once the number at one cavity passes a threshold — roughly fifteen bees — the scouts switch from advertising to a signal that tells the whole swarm to prepare for take-off. The quorum works because reaching it almost always means one site has decisively out-competed the rest. Waiting for unanimity would be slower and no more accurate.

E   Researchers who study this process argue that it holds lessons for human groups. A swarm decides well because its members investigate independently, share honest assessments in proportion to what they found, and let support accumulate rather than deferring to a leader — the colony, in fact, has no leader, not even the queen. Committees that copy these features — independent judgement, frank reporting, and a clear threshold for action — tend to make better decisions than those dominated by the loudest or most senior voice.

It is easy to assume that the public park — that ordinary stretch of grass, trees and paths open to anyone — has always existed. In fact it is largely a nineteenth-century invention, and a deliberate one. Before industrialisation, most people lived close to fields and woods, while the few landscaped parks that existed were private, the gardens of palaces and great houses, closed to the general population. The idea that a city should set aside large areas of green specifically for the use of all its citizens was, at the time, genuinely radical.

The change was driven by crisis. The industrial city of the early nineteenth century was overcrowded and polluted, its working districts packed with housing and almost devoid of open space. Reformers, including doctors alarmed by repeated epidemics, began to argue that cities needed green space in the way a body needs to breathe. Parks, they said, would act as the “lungs of the city”, places where the poor could find fresh air, exercise and relief from the surrounding density. The phrase was rhetorical, but it captured a real conviction that access to nature was a matter of public health, not luxury.

There was a social argument too. Supporters hoped that a well-kept park would be a shared public space in which different classes might mix peacefully, and in which the habits of the crowded slum might give way to calmer behaviour. Whether parks ever truly mixed the classes is doubtful, but the aspiration shaped their design. Early municipal parks were not intended to display a city’s wealth so much as to improve its people.

The way these parks looked was carefully considered. Rather than the geometric avenues of aristocratic gardens, designers favoured winding paths, irregular lakes and clumps of trees arranged to imitate the countryside. The aim was to give a city dweller, within a short walk of home, the experience of being somewhere rural and restful. This naturalistic style, pioneered in Britain and copied across Europe and North America, became the template for the urban park almost everywhere.

The original arguments have proved unexpectedly durable. Today parks are valued not only for recreation but for measurable environmental services: they lower urban temperatures during heatwaves, absorb rainfall that would otherwise overwhelm drains, and support wildlife in otherwise hostile cities. The Victorian reformers spoke metaphorically when they called parks the lungs of the city; modern researchers, measuring air, heat and water, have given the metaphor a literal edge. The public park, invented to solve the problems of the first industrial age, turns out to be useful for the problems of the present one.